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Bakhiet A, Passmore W, Nath U, Das A, Pillai A. Can a Fully Electronic Patient Record-Based Virtual Fracture Clinic Increase Compliance With British Orthopaedic Association Guidelines for the Assessment of Acute Orthopaedic Trauma Patients? Cureus 2023; 15:e46942. [PMID: 37841983 PMCID: PMC10570870 DOI: 10.7759/cureus.46942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/13/2023] [Indexed: 10/17/2023] Open
Abstract
Introduction There is clear guidance for the follow-up of acute orthopaedic trauma patients within 72 hours of presentation as per British Orthopaedic Association (BOA) guidelines. The virtual fracture clinic (VFC) model has been adopted nationwide to increase compliance with these guidelines. Traditionally our VFC was paper-based, but recently it has been made completely electronic with the introduction of Hive which is a comprehensive electronic patient record (EPR). The aim of this audit was to assess the effectiveness of the Hive VFC and to see the impact it has on improving the patient experience. Methods Data was collected retrospectively by looking at referrals to the Hive VFC across a seven-month period from its date of introduction. No patients were excluded and data was collected for 2,158 patients. Patient demographics, referral details, and outcomes were recorded on a Microsoft Excel version 16.0 for Windows spreadsheet (Microsoft Corporation, Washington, United States). Data was analysed using Microsoft Excel. Results Data was collected for 2,158 patients between September 9, 2022, and March 31, 2023, in the Hive VFC. The largest proportion of injuries was found in the foot and ankle region with 32% of referrals (n=688), followed by hand and wrist with 30% (n=651), upper limb with 28% (n=595), and lower limb with 7% (n=142). There was a 50.4% (n=125) increase in the number of patients seen in the VFC across the study period with 248 patients being seen in September 2022, increasing to 373 in March 2023. The number of patients with acute traumatic orthopaedic injuries that were assessed within 72 hours on average was 94.5% per month. There was an increase of 7.3% during the study period from September 2022 to March 2023, 89.9% to 96.5%, respectively. Conclusion We believe that Hive VFC is a clinically sound and effective way of assessing acute traumatic orthopaedic patients and increasing compliance with BOA and NICE guidelines. The number of patients needing acute orthopaedic assessment is rising steadily, and this should alert us to find more convenient, time and cost-saving methods of delivering safe and effective patient care.
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Affiliation(s)
- Abdelwakeel Bakhiet
- Trauma and Orthopaedics, Wythenshawe Hospital, Manchester University National Health Service (NHS) Foundation Trust, Manchester, GBR
| | - William Passmore
- Trauma and Orthopaedics, University of Manchester, Manchester, GBR
| | - Upamanyu Nath
- Trauma and Orthopaedics, Wythenshawe Hospital, Manchester University National Health Service (NHS) Foundation Trust, Manchester, GBR
| | - Abhirun Das
- Trauma and Orthopaedics, Wythenshawe Hospital, Manchester University National Health Service (NHS) Foundation Trust, Manchester, GBR
| | - Anand Pillai
- Trauma and Orthopaedics, Wythenshawe Hospital, Manchester University National Health Service (NHS) Foundation Trust, Manchester, GBR
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Steffens S, Antell EH, Cook EK, Rao G, Britt RD, Sedlak DL, Alvarez-Cohen L. An Artifact of Perfluoroalkyl Acid (PFAA) Removal Attributed to Sorption Processes in a Laccase Mediator System. Environ Sci Technol Lett 2023; 10:337-342. [PMID: 37064824 PMCID: PMC10100556 DOI: 10.1021/acs.estlett.3c00173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 03/21/2023] [Accepted: 03/22/2023] [Indexed: 06/19/2023]
Abstract
Fungi and laccase mediator systems (LMSs) have a proven track record of oxidizing recalcitrant organic compounds. There has been considerable interest in applying LMSs to the treatment of perfluoroalkyl acids (PFAAs), a class of ubiquitous and persistent environmental contaminants. Some laboratory experiments have indicated modest losses of PFAAs over extended periods, but there have been no clear demonstrations of a transformation mechanism or the kinetics that would be needed for remediation applications. We set out to determine if this was a question of identifying and optimizing a rate-limiting step but discovered that observed losses of PFAAs were experimental artifacts. While unable to replicate the oxidation of PFAAs, we show that interactions of the PFAA compounds with laccase and laccase mediator mixtures could cause an artifact that mimics transformation (≲60%) of PFAAs. Furthermore, we employed a surrogate compound, carbamazepine (CBZ), and electron paramagnetic resonance spectroscopy to probe the formation of the radical species that had been proposed to be responsible for contaminant oxidation. We confirmed that under conditions where sufficient radical concentrations were produced to oxidize CBZ, no PFAA removal took place.
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Affiliation(s)
- Sophia
D. Steffens
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
| | - Edmund H. Antell
- Department
of Civil and Environmental Engineering, University of California, Berkeley, California 94720, United States
| | - Emily K. Cook
- Department
of Civil and Environmental Engineering, University of California, Berkeley, California 94720, United States
| | - Guodong Rao
- Department
of Chemistry, University of California, Davis, California 95616, United States
| | - R. David Britt
- Department
of Chemistry, University of California, Davis, California 95616, United States
| | - David L. Sedlak
- Department
of Civil and Environmental Engineering, University of California, Berkeley, California 94720, United States
| | - Lisa Alvarez-Cohen
- Department
of Civil and Environmental Engineering, University of California, Berkeley, California 94720, United States
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3
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Adjei D, Reyes Y, Kumar A, Ward S, Denisov SA, Alahmadi M, Sevilla MD, Wnuk SF, Mostafavi M, Adhikary A. Pathways of the Dissociative Electron Attachment Observed in 5- and 6-Azidomethyluracil Nucleosides: Nitrogen (N 2) Elimination vs Azide Anion (N 3-) Elimination. J Phys Chem B 2023; 127:1563-1571. [PMID: 36780335 PMCID: PMC9984991 DOI: 10.1021/acs.jpcb.2c08257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Abstract
5-Azidomethyl-2'-deoxyuridine (5-AmdU, 1) has been successfully employed for the metabolic labeling of DNA and fluorescent imaging of live cells. 5-AmdU also demonstrated significant radiosensitization in breast cancer cells via site-specific nitrogen-centered radical (π-aminyl (U-5-CH2-NH•), 2, and σ-iminyl (U-5-CH═N•), 3) formation. This work shows that these nitrogen-centered radicals are not formed via the reduction of the azido group in 6-azidomethyluridine (6-AmU, 4). Radical assignments were performed using electron spin resonance (ESR) in supercooled solutions, pulse radiolysis in aqueous solutions, and theoretical (DFT) calculations. Radiation-produced electron addition to 4 leads to the facile N3- loss, forming a stable neutral C-centered allylic radical (U-6-CH2•, 5) through dissociative electron attachment (DEA) via the transient negative ion, TNI (U-6-CH2-N3•-), in agreement with DFT calculations. In contrast, TNI (U-5-CH2-N3•-) of 1, via facile N2 loss (DEA) and protonation from the surrounding water, forms radical 2. Subsequently, 2 undergoes rapid H-atom abstraction from 1 and produces the metastable intermediate α-azidoalkyl radical (U-5-CH•-N3). U-5-CH•-N3 converts facilely to radical 3. N3- loss from U-6-CH2-N3•- is thermodynamically controlled, whereas N2 loss from U-5-CH2-N3•- is dictated by protonation from the surrounding waters and resonance conjugation of the azidomethyl side chain at C5 with the pyrimidine ring.
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Affiliation(s)
- Daniel Adjei
- Institut de Chimie Physique, UMR 8000 CNRS, Bât. 349, Université Paris-Saclay; 91405, Orsay, Cedex, France
| | - Yahaira Reyes
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, USA
| | - Anil Kumar
- Department of Chemistry, 146 Library Drive, Oakland University, Rochester, Michigan 48309, USA
| | - Samuel Ward
- Department of Chemistry, 146 Library Drive, Oakland University, Rochester, Michigan 48309, USA
| | - Sergey A. Denisov
- Institut de Chimie Physique, UMR 8000 CNRS, Bât. 349, Université Paris-Saclay; 91405, Orsay, Cedex, France
| | - Moaadh Alahmadi
- Department of Chemistry, 146 Library Drive, Oakland University, Rochester, Michigan 48309, USA
| | - Michael D. Sevilla
- Department of Chemistry, 146 Library Drive, Oakland University, Rochester, Michigan 48309, USA
| | - Stanislaw F. Wnuk
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, USA
| | - Mehran Mostafavi
- Institut de Chimie Physique, UMR 8000 CNRS, Bât. 349, Université Paris-Saclay; 91405, Orsay, Cedex, France
| | - Amitava Adhikary
- Department of Chemistry, 146 Library Drive, Oakland University, Rochester, Michigan 48309, USA
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4
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Devonport J, Sully L, Boudalis AK, Hassell-Hart S, Leech MC, Lam K, Abdul-Sada A, Tizzard GJ, Coles SJ, Spencer J, Vargas A, Kostakis GE. Room-Temperature Cu(II) Radical-Triggered Alkyne C-H Activation. JACS Au 2021; 1:1937-1948. [PMID: 34841411 PMCID: PMC8611675 DOI: 10.1021/jacsau.1c00310] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Indexed: 06/13/2023]
Abstract
A dimeric Cu(II) complex [Cu(II)2L2(μ2-Cl)Cl] (1) built from an asymmetric tridentate ligand (2-(((2-aminocyclohexyl)imino)methyl)-4,6-di-tert-butylphenol) and weakly coordinating anions has been synthesized and structurally characterized. In dichloromethane solution, 1 exists in a monomeric [Cu(II)LCl] (1') (85%)-dimeric (1) (15%) equilibrium, and cyclic voltammetry (CV) and electron paramagnetic resonance (EPR) studies indicate structural stability and redox retention. Addition of phenylacetylene to the CH2Cl2 solution populates 1' and leads to the formation of a transient radical species. Theoretical studies support this notion and show that the radical initiates an alkyne C-H bond activation process via a four-membered ring (Cu(II)-O···H-Calkyne) intermediate. This unusual C-H activation method is applicable for the efficient synthesis of propargylamines, without additives, within 16 h, at low loadings and in noncoordinating solvents including late-stage functionalization of important bioactive molecules. Single-crystal X-ray diffraction studies, postcatalysis, confirmed the framework's stability and showed that the metal center preserves its oxidation state. The scope and limitations of this unconventional protocol are discussed.
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Affiliation(s)
- Jack Devonport
- Department
of Chemistry, School of Life Sciences, University
of Sussex, Brighton BN1 9QJ, U.K.
| | - Lauren Sully
- Department
of Chemistry, School of Life Sciences, University
of Sussex, Brighton BN1 9QJ, U.K.
| | - Athanassios K. Boudalis
- Institut
de Chimie de Strasbourg (UMR 7177, CNRS-Unistra), Université
de Strasbourg, 4 rue Blaise Pascal, CS 90032, F-67081 Strasbourg, France
- Université
de Strasbourg, CNRS, Institut de Physique et Chimie des Matériaux
de Strasbourg (IPCMS), UMR 7504, F-67000 Strasbourg, France
| | - Storm Hassell-Hart
- Department
of Chemistry, School of Life Sciences, University
of Sussex, Brighton BN1 9QJ, U.K.
| | - Matthew C. Leech
- School
of Science, Department of Pharmaceutical Chemical and Environmental
Sciences, University of Greenwich, Central Avenue, Chatham Maritime ME4 4TB, U.K.
| | - Kevin Lam
- School
of Science, Department of Pharmaceutical Chemical and Environmental
Sciences, University of Greenwich, Central Avenue, Chatham Maritime ME4 4TB, U.K.
| | - Alaa Abdul-Sada
- Department
of Chemistry, School of Life Sciences, University
of Sussex, Brighton BN1 9QJ, U.K.
| | - Graham J. Tizzard
- UK
National Crystallography Service, Chemistry, University of Southampton, Southampton SO1 71BJ, U.K.
| | - Simon J. Coles
- UK
National Crystallography Service, Chemistry, University of Southampton, Southampton SO1 71BJ, U.K.
| | - John Spencer
- Department
of Chemistry, School of Life Sciences, University
of Sussex, Brighton BN1 9QJ, U.K.
| | - Alfredo Vargas
- Department
of Chemistry, School of Life Sciences, University
of Sussex, Brighton BN1 9QJ, U.K.
| | - George E. Kostakis
- Department
of Chemistry, School of Life Sciences, University
of Sussex, Brighton BN1 9QJ, U.K.
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Abstract
The decoherence, or dephasing, of electron spins in paramagnetic molecules limits sensitivity and resolution in electron paramagnetic resonance spectroscopy, and it represents a challenge for utilizing paramagnetic molecules as qubit units in quantum information devices. For organic radicals in dilute frozen aqueous solution at cryogenic temperatures, electron spin decoherence is driven by neighboring nuclear spins. Here, we show that this nuclear-spin-driven decoherence can be quantitatively predicted from the molecular structure and solvation geometry of the radicals. We use a fully deterministic quantum model of the electron spin and up to 2000 neighboring protons with a static spin Hamiltonian that includes nucleus-nucleus couplings. We present experiments and simulations of two nitroxide radicals and one trityl radical, which have decoherence time scales of 4-5 μs below 60 K. We show that nuclei within 12 Å of the electron spin contribute to decoherence, with the strongest impact from protons 4-8 Å away.
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6
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Niedbalski P, Parish C, Wang Q, Hayati Z, Song L, Martins AF, Sherry AD, Lumata L. Transition Metal Doping Reveals Link between Electron T 1 Reduction and 13C Dynamic Nuclear Polarization Efficiency. J Phys Chem A 2017; 121:9221-9228. [PMID: 29125294 PMCID: PMC5793213 DOI: 10.1021/acs.jpca.7b09448] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Optimal efficiency of dissolution dynamic nuclear polarization (DNP) is essential to provide the required high sensitivity enhancements for in vitro and in vivo hyperpolarized 13C nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI). At the nexus of the DNP process are the free electrons, which provide the high spin alignment that is transferred to the nuclear spins. Without changing DNP instrumental conditions, one way to improve 13C DNP efficiency is by adding trace amounts of paramagnetic additives such as lanthanide (e.g., Gd3+, Ho3+, Dy3+, Tb3+) complexes to the DNP sample, which has been observed to increase solid-state 13C DNP signals by 100-250%. Herein, we have investigated the effects of paramagnetic transition metal complex R-NOTA (R = Mn2+, Cu2+, Co2+) doping on the efficiency of 13C DNP using trityl OX063 as the polarizing agent. Our DNP results at 3.35 T and 1.2 K show that doping the 13C sample with 3 mM Mn2+-NOTA led to a substantial improvement of the solid-state 13C DNP signal by a factor of nearly 3. However, the other transition metal complexes Cu2+-NOTA and Co2+-NOTA complexes, despite their paramagnetic nature, had essentially no impact on solid-state 13C DNP enhancement. W-band electron paramagnetic resonance (EPR) measurements reveal that the trityl OX063 electron T1 was significantly reduced in Mn2+-doped samples but not in Cu2+- and Co2+-doped DNP samples. This work demonstrates, for the first time, that not all paramagnetic additives are beneficial to DNP. In particular, our work provides a direct evidence that electron T1 reduction of the polarizing agent by a paramagnetic additive is an essential requirement for the improvement seen in solid-state 13C DNP signal.
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Affiliation(s)
- Peter Niedbalski
- Department of Physics, The University of Texas at Dallas, Richardson, TX 75080, USA
| | - Christopher Parish
- Department of Physics, The University of Texas at Dallas, Richardson, TX 75080, USA
| | - Qing Wang
- Department of Physics, The University of Texas at Dallas, Richardson, TX 75080, USA
| | - Zahra Hayati
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
| | - Likai Song
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
| | - André F. Martins
- Advanced Imaging Research Center, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Chemistry, The University of Texas at Dallas, Richardson, TX 75080, USA
| | - A. Dean Sherry
- Advanced Imaging Research Center, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Chemistry, The University of Texas at Dallas, Richardson, TX 75080, USA
| | - Lloyd Lumata
- Department of Physics, The University of Texas at Dallas, Richardson, TX 75080, USA
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7
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Abstract
Since the original observation by Zeeman, that spectral lines can be affected by magnetic fields, 'magnetic spectroscopy' has evolved into the broad arsenal of techniques known as 'magnetic resonance'. This review focuses on nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), and muon spin resonance (μSR): methods which have provided unparalleled insight into the structures, reactivity and dynamics of molecules, and thereby contributed to a detailed understanding of important aspects of chemistry, and the materials, biomedical, and environmental sciences. Magnetic resonance imaging (MRI), in vivo magnetic resonance spectroscopy (MRS) and functional magnetic resonance spectroscopy (fMRS) are also described. EPR is outlined as a principal method for investigating free radicals, along with biomedical applications, and mention is given to the more recent innovation of pulsed EPR techniques. In the final section of the article, the various methods known as μSR are collected under the heading 'muon spin resonance', in order to emphasise their complementarity with the more familiar NMR and EPR.
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8
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Hayes EC, Porter TR, Barrows CJ, Kaminsky W, Mayer JM, Stoll S. Electronic Structure of a Cu(II)-Alkoxide Complex Modeling Intermediates in Copper-Catalyzed Alcohol Oxidations. J Am Chem Soc 2016; 138:4132-45. [PMID: 26907976 PMCID: PMC4988936 DOI: 10.1021/jacs.5b13088] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In the copper-catalyzed oxidation of alcohols to aldehydes, a Cu(II)-alkoxide (Cu(II)-OR) intermediate is believed to modulate the αC-H bond strength of the deprotonated substrate to facilitate the oxidation. As a structural model for these intermediates, we characterized the electronic structure of the stable compound Tp(tBu)Cu(II)(OCH2CF3) (Tp(tBu) = hydro-tris(3-tert-butyl-pyrazolyl)borate) and investigated the influence of the trifluoroethoxide ligand on the electronic structure of the complex. The compound exhibits an electron paramagnetic resonance (EPR) spectrum with an unusually large gzz value of 2.44 and a small copper hyperfine coupling Azz of 40 × 10(-4) cm(-1) (120 MHz). Single-crystal electron nuclear double resonance (ENDOR) spectra show that the unpaired spin population is highly localized on the copper ion (≈68%), with no more than 15% on the ethoxide oxygen. Electronic absorption and magnetic circular dichroism (MCD) spectra show weak ligand-field transitions between 5000 and 12,000 cm(-1) and an intense ethoxide-to-copper charge transfer (LMCT) transition at 24,000 cm(-1), resulting in the red color of this complex. Resonance Raman (rR) spectroscopy reveals a Cu-O stretch mode at 592 cm(-1). Quantum chemical calculations support the interpretation and assignment of the experimental data. Compared to known Cu(II)-thiolate and Cu(II)-alkylperoxo complexes from the literature, we found an increased σ interaction in the Cu(II)-OR bond that results in the spectroscopic features. These insights lay the basis for further elucidating the mechanism of copper-catalyzed alcohol oxidations.
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Affiliation(s)
- Ellen C. Hayes
- Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195
| | | | - Charles J. Barrows
- Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195
| | - Werner Kaminsky
- Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195
| | | | - Stefan Stoll
- Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195
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9
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Zhen Z, Tang W, Chuang YJ, Todd T, Zhang W, Lin X, Niu G, Liu G, Wang L, Pan Z, Chen X, Xie J. Tumor vasculature targeted photodynamic therapy for enhanced delivery of nanoparticles. ACS Nano 2014; 8:6004-13. [PMID: 24806291 PMCID: PMC4076019 DOI: 10.1021/nn501134q] [Citation(s) in RCA: 181] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 05/07/2014] [Indexed: 05/18/2023]
Abstract
Delivery of nanoparticle drugs to tumors relies heavily on the enhanced permeability and retention (EPR) effect. While many consider the effect to be equally effective on all tumors, it varies drastically among the tumors' origins, stages, and organs, owing much to differences in vessel leakiness. Suboptimal EPR effect represents a major problem in the translation of nanomedicine to the clinic. In the present study, we introduce a photodynamic therapy (PDT)-based EPR enhancement technology. The method uses RGD-modified ferritin (RFRT) as "smart" carriers that site-specifically deliver (1)O2 to the tumor endothelium. The photodynamic stimulus can cause permeabilized tumor vessels that facilitate extravasation of nanoparticles at the sites. The method has proven to be safe, selective, and effective. Increased tumor uptake was observed with a wide range of nanoparticles by as much as 20.08-fold. It is expected that the methodology can find wide applications in the area of nanomedicine.
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Affiliation(s)
- Zipeng Zhen
- Department of Chemistry, University, of Georgia, Athens, Georgia 30602, United States
| | - Wei Tang
- Department of Chemistry, University, of Georgia, Athens, Georgia 30602, United States
| | - Yen-Jun Chuang
- Department of Physics, University of Georgia, Athens, Georgia 30602, United States
| | - Trever Todd
- Department of Chemistry, University, of Georgia, Athens, Georgia 30602, United States
| | - Weizhong Zhang
- Department of Chemistry, University, of Georgia, Athens, Georgia 30602, United States
| | - Xin Lin
- National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), Bethesda, Maryland 20852, United States
| | - Gang Niu
- National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), Bethesda, Maryland 20852, United States
| | - Gang Liu
- Key Laboratory of Molecular Vaccinology and Molecular Diagnostics & Center for Molecular Imaging and Translational Medicine, School of Public Health, Xiamen University, Xiamen, 361102, China
| | - Lianchun Wang
- Department of Biochemistry and Complex Carbohydrate Research Center (CCRC), University of Georgia, Athens, Georgia 30602, United States
| | - Zhengwei Pan
- Department of Physics, University of Georgia, Athens, Georgia 30602, United States
| | - Xiaoyuan Chen
- National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), Bethesda, Maryland 20852, United States
| | - Jin Xie
- Department of Chemistry, University, of Georgia, Athens, Georgia 30602, United States
- Bio-Imaging Research Center (BIRC), University of Georgia, Athens, Georgia 30602, United States
- Address correspondence to
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10
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Williams BB, Flood AB, Salikhov I, Kobayashi K, Dong R, Rychert K, Du G, Schreiber W, Swartz HM. In vivo EPR tooth dosimetry for triage after a radiation event involving large populations. Radiat Environ Biophys 2014; 53:335-46. [PMID: 24711003 PMCID: PMC11064839 DOI: 10.1007/s00411-014-0534-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 02/27/2014] [Indexed: 05/26/2023]
Abstract
The management of radiation injuries following a catastrophic event where large numbers of people may have been exposed to life-threatening doses of ionizing radiation will rely critically on the availability and use of suitable biodosimetry methods. In vivo electron paramagnetic resonance (EPR) tooth dosimetry has a number of valuable and unique characteristics and capabilities that may help enable effective triage. We have produced a prototype of a deployable EPR tooth dosimeter and tested it in several in vitro and in vivo studies to characterize the performance and utility at the state of the art. This report focuses on recent advances in the technology, which strengthen the evidence that in vivo EPR tooth dosimetry can provide practical, accurate, and rapid measurements in the context of its intended use to help triage victims in the event of an improvised nuclear device. These advances provide evidence that the signal is stable, accurate to within 0.5 Gy, and can be successfully carried out in vivo. The stability over time of the radiation-induced EPR signal from whole teeth was measured to confirm its long-term stability and better characterize signal behavior in the hours following irradiation. Dosimetry measurements were taken for five pairs of natural human upper central incisors mounted within a simple anatomic mouth model that demonstrates the ability to achieve 0.5 Gy standard error of inverse dose prediction. An assessment of the use of intact upper incisors for dose estimation and screening was performed with volunteer subjects who have not been exposed to significant levels of ionizing radiation and patients who have undergone total body irradiation as part of bone marrow transplant procedures. Based on these and previous evaluations of the performance and use of the in vivo tooth dosimetry system, it is concluded that this system could be a very valuable resource to aid in the management of a massive radiological event.
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Affiliation(s)
- Benjamin B Williams
- Department of Radiology, EPR Center for the Study of Viable Systems, Geisel School of Medicine at Dartmouth, Hanover, NH, USA,
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11
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Wieser A, Vasilenko E, Aladova E, Fattibene P, Semiochkina N, Smetanin M. Electron paramagnetic resonance measurements of absorbed dose in teeth from citizens of Ozyorsk. Radiat Environ Biophys 2014; 53:321-333. [PMID: 24604722 PMCID: PMC3996272 DOI: 10.1007/s00411-014-0527-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 02/21/2014] [Indexed: 06/03/2023]
Abstract
In 1945, within the frame of the Uranium Project for the production of nuclear weapons, the Mayak nuclear facilities were constructed at the Lake Irtyash in the Southern Urals, Russia. The nuclear workers of the Mayak Production Association (MPA), who lived in the city of Ozyorsk, are the focus of epidemiological studies for the assessment of health risks due to protracted exposure to ionising radiation. Electron paramagnetic resonance measurements of absorbed dose in tooth enamel have already been used in the past, in an effort to validate occupational external doses that were evaluated in the Mayak Worker Dosimetry System. In the present study, 229 teeth of Ozyorsk citizens not employed at MPA were investigated for the assessment of external background exposure in Ozyorsk. The annually absorbed dose in tooth enamel from natural background radiation was estimated to be (0.7 ± 0.3) mGy. For citizens living in Ozyorsk during the time of routine noble gas releases of the MPA, which peaked in 1953, the average excess absorbed dose in enamel above natural background was (36 ± 29) mGy, which is consistent with the gamma dose obtained by model calculations. In addition, there were indications of possible accidental gaseous MPA releases that affected the population of Ozyorsk, during the early and late MPA operation periods, before 1951 and after 1960.
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Affiliation(s)
- A Wieser
- Institute of Radiation Protection, Helmholtz Zentrum München - German Research Center for Environmental Health, 85764, Neuherberg, Germany,
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12
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Kunjachan S, Pola R, Gremse F, Theek B, Ehling J, Moeckel D, Hermanns-Sachweh B, Pechar M, Ulbrich K, Hennink WE, Storm G, Lederle W, Kiessling F, Lammers T. Passive versus active tumor targeting using RGD- and NGR-modified polymeric nanomedicines. Nano Lett 2014; 14:972-81. [PMID: 24422585 PMCID: PMC3940962 DOI: 10.1021/nl404391r] [Citation(s) in RCA: 239] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Enhanced permeability and retention (EPR) and the (over-) expression of angiogenesis-related surface receptors are key features of tumor blood vessels. As a consequence, EPR-mediated passive and Arg-Gly-Asp (RGD) and Asn-Gly-Arg (NGR) based active tumor targeting have received considerable attention in the last couple of years. Using several different in vivo and ex vivo optical imaging techniques, we here visualized and quantified the benefit of RGD- and NGR-based vascular vs EPR-mediated passive tumor targeting. This was done using ∼ 10 nm sized polymeric nanocarriers, which were either labeled with DY-676 (peptide-modified polymers) or with DY-750 (peptide-free polymers). Upon coinjection into mice bearing both highly leaky CT26 and poorly leaky BxPC3 tumors, it was found that vascular targeting did work, resulting in rapid and efficient early binding to tumor blood vessels, but that over time, passive targeting was significantly more efficient, leading to higher overall levels and to more efficient retention within tumors. Although this situation might be different for larger carrier materials, these insights indicate that caution should be taken not to overestimate the potential of active over passive tumor targeting.
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Affiliation(s)
- Sijumon Kunjachan
- Dept. of Experimental Molecular Imaging, University Hospital and Helmholtz Institute for Biomedical Engineering, RWTH Aachen, Pauwelsstrasse 30, 52074 Aachen, Germany
| | - Robert Pola
- Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Square 2, 162 06 Prague 6, Czech Republic
| | - Felix Gremse
- Dept. of Experimental Molecular Imaging, University Hospital and Helmholtz Institute for Biomedical Engineering, RWTH Aachen, Pauwelsstrasse 30, 52074 Aachen, Germany
| | - Benjamin Theek
- Dept. of Experimental Molecular Imaging, University Hospital and Helmholtz Institute for Biomedical Engineering, RWTH Aachen, Pauwelsstrasse 30, 52074 Aachen, Germany
| | - Josef Ehling
- Dept. of Experimental Molecular Imaging, University Hospital and Helmholtz Institute for Biomedical Engineering, RWTH Aachen, Pauwelsstrasse 30, 52074 Aachen, Germany
| | - Diana Moeckel
- Dept. of Experimental Molecular Imaging, University Hospital and Helmholtz Institute for Biomedical Engineering, RWTH Aachen, Pauwelsstrasse 30, 52074 Aachen, Germany
| | - Benita Hermanns-Sachweh
- Electron Microscopy, Institute of Pathology, Medical Faculty, RWTH Aachen, Pauwelstrasse 30, 52074 Aachen, Germany
| | - Michal Pechar
- Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Square 2, 162 06 Prague 6, Czech Republic
| | - Karel Ulbrich
- Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Square 2, 162 06 Prague 6, Czech Republic
| | - Wim E. Hennink
- Dept. of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
| | - Gert Storm
- Dept. of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
- Dept. of Controlled Drug Delivery, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, PO Box 217, 7500 AE, Enschede, The Netherlands
| | - Wiltrud Lederle
- Dept. of Experimental Molecular Imaging, University Hospital and Helmholtz Institute for Biomedical Engineering, RWTH Aachen, Pauwelsstrasse 30, 52074 Aachen, Germany
| | - Fabian Kiessling
- Dept. of Experimental Molecular Imaging, University Hospital and Helmholtz Institute for Biomedical Engineering, RWTH Aachen, Pauwelsstrasse 30, 52074 Aachen, Germany
| | - Twan Lammers
- Dept. of Experimental Molecular Imaging, University Hospital and Helmholtz Institute for Biomedical Engineering, RWTH Aachen, Pauwelsstrasse 30, 52074 Aachen, Germany
- Dept. of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
- Dept. of Controlled Drug Delivery, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, PO Box 217, 7500 AE, Enschede, The Netherlands
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Yang Y, Ramelot TA, Ni S, McCarrick RM, Kennedy MA. Applications of NMR-based PRE and EPR-based DEER spectroscopy to homodimer chain exchange characterization and structure determination. Methods Mol Biol 2014; 1091:215-27. [PMID: 24203336 PMCID: PMC4075034 DOI: 10.1007/978-1-62703-691-7_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The success of homodimer structure determination by conventional solution NMR spectroscopy relies greatly on interchain distance restraints (less than 6 Å) derived from nuclear Overhauser effects (NOEs) obtained from (13)C-edited, (12)C-filtered NOESY experiments. However, these experiments may fail when the mixed (13)C-/(12)C-homodimer is never significantly populated due to slow homodimer chain exchange. Thus, knowledge of the homodimer chain exchange kinetics can be put to practical use in preparing samples using the traditional NMR method. Here, we described detailed procedures for using paramagnetic resonance enhancements (PREs) and EPR spectroscopy to measure homodimer chain exchange kinetics. In addition, PRE and EPR methods can be combined to provide mid-range (<30 Å) and long-range (17-80 Å) interchain distance restraints for homodimer structure determination as a supplement to short-range intrachain and interchain distance restraints (less than 6 Å) typically obtained from (1)H-(1)H NOESY experiments. We present a summary of how to measure these distances using NMR-based PREs and EPR-based double electron electron resonance (DEER) measurements and how to include them in homodimer structure calculations.
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Affiliation(s)
- Yunhuang Yang
- Department of Chemistry and Biochemistry, and the Northeast Structural Genomics Consortium, Miami University, Oxford, Ohio, USA, 45056,To whom correspondence should be addressed. Tel: +1 523 529 8267; Fax: +1 513 529 5715; and
| | - Theresa A. Ramelot
- Department of Chemistry and Biochemistry, and the Northeast Structural Genomics Consortium, Miami University, Oxford, Ohio, USA, 45056
| | - Shuisong Ni
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio, USA, 45056
| | - Robert M. McCarrick
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio, USA, 45056
| | - Michael A. Kennedy
- Department of Chemistry and Biochemistry, and the Northeast Structural Genomics Consortium, Miami University, Oxford, Ohio, USA, 45056,To whom correspondence should be addressed. Tel: +1 523 529 8267; Fax: +1 513 529 5715; and
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14
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Abstract
An overview is provided of the importance of molecular species containing unpaired electrons in catalytic systems, as revealed using ESR spectroscopy. The review aims to demonstrate the considerable extent of scientific progress that has been made in this broad topic during the past few decades. Studies of catalytically active surfaces, including zeolites, are surveyed, and the detection of radical species, formed as intermediates in their reactions, using matrix isolation and spin-trapping techniques. Radical cation formation in zeolites is discussed, and the employment of muon spin rotation and relaxation techniques to study the mobility of labelled radicals in various porous and catalytic media. Among the specific types of catalytic media considered are those for photocatalysis, water splitting, degradation of environmental pollutants, hydrocarbon conversions, fuel cells and sensor devices employing graphene. The review concludes with recent developments in the study of enzymes and their reactions, using ESR-based methods.
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Mainali L, Raguz M, O’Brien WJ, Subczynski WK. Properties of membranes derived from the total lipids extracted from the human lens cortex and nucleus. Biochim Biophys Acta 2013; 1828:1432-40. [PMID: 23438364 PMCID: PMC3633468 DOI: 10.1016/j.bbamem.2013.02.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 02/08/2013] [Accepted: 02/14/2013] [Indexed: 11/21/2022]
Abstract
Human lens lipid membranes prepared using a rapid solvent exchange method from the total lipids extracted from the clear lens cortex and nucleus of 41- to 60-year-old donors were investigated using electron paramagnetic resonance spin-labeling. Profiles of the phospholipid alkyl-chain order, fluidity, oxygen transport parameter, and hydrophobicity were assessed across coexisting membrane domains. Membranes prepared from the lens cortex and nucleus were found to contain two distinct lipid environments, the bulk phospholipid-cholesterol domain and the cholesterol bilayer domain (CBD). The alkyl chains of phospholipids were strongly ordered at all depths, indicating that the amplitude of the wobbling motion of alkyl chains was small. However, profiles of the membrane fluidity, which explicitly contain time (expressed as the spin-lattice relaxation rate) and depend on the rotational motion of spin labels, show relatively high fluidity of alkyl chains close to the membrane center. Profiles of the oxygen transport parameter and hydrophobicity have a rectangular shape and also indicate a high fluidity and hydrophobicity of the membrane center. The amount of CBD was greater in nuclear membranes than in cortical membranes. The presence of the CBD in lens lipid membranes, which at 37°C showed a permeability coefficient for oxygen about 60% smaller than across a water layer of the same thickness, would be expected to raise the barrier for oxygen transport across the fiber cell membrane. Properties of human membranes are compared with those obtained for membranes made of lipids extracted from cortex and nucleus of porcine and bovine eye lenses.
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Affiliation(s)
- Laxman Mainali
- Department of Biophysics, Milwaukee, WI 53226, USA
- Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Marija Raguz
- Department of Biophysics, Milwaukee, WI 53226, USA
- Medical College of Wisconsin, Milwaukee, WI 53226, USA
- Department of Medical Physics and Biophysics, School of Medicine, University of Split, Split, Croatia
| | - William J. O’Brien
- Department of Ophthalmology and Microbiology/Molecular Genetics, Milwaukee, WI 53226, USA
- Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Witold K. Subczynski
- Department of Biophysics, Milwaukee, WI 53226, USA
- Medical College of Wisconsin, Milwaukee, WI 53226, USA
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Edeghere O, Shankar G, Bartholomew A, Ramachandra S, Singh V, Banandur P, Parr L, Yap K, Olowokure B, Ibbotson S. International Collaboration for Improved Public Health Emergency Preparedness and Response in India. Online J Public Health Inform 2013. [PMCID: PMC3692801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Objective Introduction Methods Results Conclusions
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Affiliation(s)
- Obaghe Edeghere
- The Health Protection Agency, Birmingham, United Kingdom;,Obaghe Edeghere, E-mail:
| | - Giri Shankar
- The Health Protection Agency, Birmingham, United Kingdom
| | | | | | - Vivek Singh
- Indian Institute of Public Health, Hyderabad, India
| | | | - Linda Parr
- The Health Protection Agency, Birmingham, United Kingdom
| | - Kenny Yap
- The Health Protection Agency, Birmingham, United Kingdom
| | | | - Sue Ibbotson
- The Health Protection Agency, Birmingham, United Kingdom
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17
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Yang Y, Ramelot TA, Ni S, McCarrick RM, Kennedy MA. Measurement of rate constants for homodimer subunit exchange using double electron-electron resonance and paramagnetic relaxation enhancements. J Biomol NMR 2013; 55:47-58. [PMID: 23180051 PMCID: PMC3697061 DOI: 10.1007/s10858-012-9685-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Accepted: 11/04/2012] [Indexed: 06/05/2023]
Abstract
Here, we report novel methods to measure rate constants for homodimer subunit exchange using double electron-electron resonance (DEER) electron paramagnetic resonance spectroscopy measurements and nuclear magnetic resonance spectroscopy based paramagnetic relaxation enhancement (PRE) measurements. The techniques were demonstrated using the homodimeric protein Dsy0195 from the strictly anaerobic bacterium Desulfitobacterium hafniense Y51. At specific times following mixing site-specific MTSL-labeled Dsy0195 with uniformly (15)N-labeled Dsy0195, the extent of exchange was determined either by monitoring the decrease of MTSL-labeled homodimer from the decay of the DEER modulation depth or by quantifying the increase of MTSL-labeled/(15)N-labeled heterodimer using PREs. Repeated measurements at several time points following mixing enabled determination of the homodimer subunit dissociation rate constant, k (-1), which was 0.037 ± 0.005 min(-1) derived from DEER experiments with a corresponding half-life time of 18.7 min. These numbers agreed with independent measurements obtained from PRE experiments. These methods can be broadly applied to protein-protein and protein-DNA complex studies.
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Affiliation(s)
- Yunhuang Yang
- Department of Chemistry and Biochemistry, and Northeast Structural Genomics Consortium (NESG), Miami University, Oxford, Ohio 45056
| | - Theresa A. Ramelot
- Department of Chemistry and Biochemistry, and Northeast Structural Genomics Consortium (NESG), Miami University, Oxford, Ohio 45056
| | - Shuisong Ni
- Department of Chemistry and Biochemistry, and Northeast Structural Genomics Consortium (NESG), Miami University, Oxford, Ohio 45056
| | - Robert M. McCarrick
- Department of Chemistry and Biochemistry, and Northeast Structural Genomics Consortium (NESG), Miami University, Oxford, Ohio 45056
| | - Michael A. Kennedy
- Department of Chemistry and Biochemistry, and Northeast Structural Genomics Consortium (NESG), Miami University, Oxford, Ohio 45056
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18
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Abstract
No chemotherapeutic drug can be effective until it is delivered to its target site. Nano-sized drug carriers are designed to transport therapeutic or diagnostic materials from the point of administration to the drug's site of action. This task requires the nanoparticle carrying the drug to complete a journey from the injection site to the site of action. The journey begins with the injection of the drug carrier into the bloodstream and continues through stages of circulation, extravasation, accumulation, distribution, endocytosis, endosomal escape, intracellular localization and-finally-action. Effective nanoparticle design should consider all of these stages to maximize drug delivery to the entire tumor and effectiveness of the treatment.
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Affiliation(s)
- Joseph W Nichols
- Department of Bioengineering, University of Utah, Salt Lake City, UT 84108
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19
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Li Y, Budamagunta MS, Luo J, Xiao W, Voss JC, Lam KS. Probing of the assembly structure and dynamics within nanoparticles during interaction with blood proteins. ACS Nano 2012; 6:9485-95. [PMID: 23106540 PMCID: PMC3922124 DOI: 10.1021/nn302317j] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Fully understanding the influence of blood proteins on the assembly structure and dynamics within nanoparticles is difficult because of the complexity of the system and the difficulty in probing the diverse elements and milieus involved. Here we show the use of site-specific labeling with spin probes and fluorophores combined with electron paramagnetic resonance (EPR) spectroscopy and fluorescence resonance energy transfer (FRET) measurements to provide insights into the molecular architecture and dynamics within nanoparticles. These tools are especially useful for determining nanoparticle stability in the context of blood proteins and lipoproteins and have allowed us to quantitatively analyze the dynamic changes in assembly structure, local stability, and cargo diffusion of a class of novel telodendrimer-based micellar nanoparticles. When combined with human plasma and individual plasma components, we find that non-cross-linked nanoparticles immediately lose their original assembly structure and release their payload upon interaction with lipoproteins. In contrast, serum albumins and immunoglobulin gamma have moderate affects on the integrity of the nanoparticles. Disulfide cross-linked nanoparticles show minimal interaction with lipoproteins and can better retain their assembly structure and payload in vitro and in vivo. We further demonstrate how the enhanced stability and release property of disulfide cross-linked nanoparticles can be reversed in reductive conditions. These findings identify factors that are crucial to the performance of nanomedicines and provide design modes to control their interplay with blood factors.
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Affiliation(s)
- Yuanpei Li
- Department of Biochemistry and Molecular Medicine, UC Davis Cancer Center, University of California Davis, Sacramento, CA 95817, USA
| | - Madhu S. Budamagunta
- Department of Biochemistry and Molecular Medicine, UC Davis Cancer Center, University of California Davis, Sacramento, CA 95817, USA
| | - Juntao Luo
- Department of Pharmacology, SUNY Upstate Cancer Research Institute, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Wenwu Xiao
- Department of Biochemistry and Molecular Medicine, UC Davis Cancer Center, University of California Davis, Sacramento, CA 95817, USA
| | - John C. Voss
- Department of Biochemistry and Molecular Medicine, UC Davis Cancer Center, University of California Davis, Sacramento, CA 95817, USA
| | - Kit S. Lam
- Department of Biochemistry and Molecular Medicine, UC Davis Cancer Center, University of California Davis, Sacramento, CA 95817, USA
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20
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Palmer J, Potter L, Johnson D, Zweier J, Ahmad R. Dual-scan acquisition for accelerated continuous-wave EPR oximetry. J Magn Reson 2012; 222:53-58. [PMID: 22820009 PMCID: PMC3423522 DOI: 10.1016/j.jmr.2012.05.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 05/11/2012] [Accepted: 05/26/2012] [Indexed: 06/01/2023]
Abstract
Statistical analysis reveals that, given a fixed acquisition time, linewidth (and thus pO(2)) can be more precisely determined from multiple scans with different modulation amplitudes and sweep widths than from a single-scan. For a Lorentzian lineshape and an unknown but spatially uniform modulation amplitude, the analysis suggests the use of two scans, each occupying half of the total acquisition time. We term this mode of scanning as dual-scan acquisition. For unknown linewidths in a range [Γ(min), Γ(max)], practical guidelines are provided for selecting the modulation amplitude and sweep width for each dual-scan component. Following these guidelines can allow for a 3-4 times reduction in spectroscopic acquisition time versus an optimized single-scan, without requiring hardware modifications. Findings are experimentally verified using L-band spectroscopy with an oxygen-sensitive particulate probe.
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Affiliation(s)
- J. Palmer
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - L.C. Potter
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - D.H. Johnson
- Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
| | - J.L. Zweier
- Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
| | - R. Ahmad
- Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
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21
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Silakov A, Olsen MT, Sproules S, Reijerse EJ, Rauchfuss TB, Lubitz W. EPR/ENDOR, Mössbauer, and quantum-chemical investigations of diiron complexes mimicking the active oxidized state of [FeFe]hydrogenase. Inorg Chem 2012; 51:8617-28. [PMID: 22800196 PMCID: PMC3420818 DOI: 10.1021/ic3013766] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Understanding the catalytic process of the heterolytic splitting and formation of molecular hydrogen is one of the key topics for the development of a future hydrogen economy. With an interest in elucidating the enzymatic mechanism of the [Fe(2)(S(2)C(2)H(4)NH)(CN)(2)(CO)(2)(μ-CO)] active center uniquely found in [FeFe]hydrogenases, we present a detailed spectroscopic and theoretical analysis of its inorganic model [Fe(2)(S(2)X)(CO)(3)(dppv)(PMe(3))](+) [dppv = cis-1,2-bis(diphenylphosphino)ethylene] in two forms with S(2)X = ethanedithiolate (1edt) and azadithiolate (1adt). These complexes represent models for the oxidized mixed-valent Fe(I)Fe(II) state analogous to the active oxidized "H(ox)" state of the native H-cluster. For both complexes, the (31)P hyperfine interactions were determined by pulse electron paramagnetic resonance and electron nuclear double resonance (ENDOR) methods. For 1edt, the (57)Fe parameters were measured by electron spin-echo envelope modulation and Mössbauer spectroscopy, while for 1adt, (14)N and selected (1)H couplings could be obtained by ENDOR and hyperfine sublevel correlation spectroscopy. The spin density was found to be predominantly localized on the Fe(dppv) site. This spin distribution is different from that of the H-cluster, where both the spin and charge densities are delocalized over the two Fe centers. This difference is attributed to the influence of the "native" cubane subcluster that is lacking in the inorganic models. The degree and character of the unpaired spin delocalization was found to vary from 1edt, with an abiological dithiolate, to 1adt, which features the authentic cofactor. For 1adt, we find two (14)N signals, which are indicative for two possible isomers of the azadithiolate, demonstrating its high flexibility. All interaction parameters were also evaluated through density functional theory calculations at various levels.
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Affiliation(s)
- Alexey Silakov
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34–36, Mülheim a.d. Ruhr, 45470, Germany
| | - Matthew T. Olsen
- Department of Chemistry, University of Illinois, A328 Chemical & Life Sciences Lab, 600 South Mathews Avenue, Urbana, IL 61801, USA
| | - Stephen Sproules
- School of Chemistry and Photon Science Institute, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Eduard J. Reijerse
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34–36, Mülheim a.d. Ruhr, 45470, Germany
| | - Thomas B. Rauchfuss
- Department of Chemistry, University of Illinois, A328 Chemical & Life Sciences Lab, 600 South Mathews Avenue, Urbana, IL 61801, USA
| | - Wolfgang Lubitz
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34–36, Mülheim a.d. Ruhr, 45470, Germany
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22
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Kittell AW, Hustedt EJ, Hyde JS. Inter-spin distance determination using L-band (1-2 GHz) non-adiabatic rapid sweep electron paramagnetic resonance (NARS EPR). J Magn Reson 2012; 221:51-6. [PMID: 22750251 PMCID: PMC3957363 DOI: 10.1016/j.jmr.2012.05.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 05/04/2012] [Accepted: 05/07/2012] [Indexed: 05/23/2023]
Abstract
Site-directed spin-labeling electron paramagnetic resonance (SDSL EPR) provides insight into the local structure and motion of a spin probe strategically attached to a molecule. When a second spin is introduced to the system, macromolecular information can be obtained through measurement of inter-spin distances either by continuous wave (CW) or pulsed electron double resonance (ELDOR) techniques. If both methodologies are considered, inter-spin distances of 8-80 Å can be experimentally determined. However, there exists a region at the upper limit of the conventional X-band (9.5 GHz) CW technique and the lower limit of the four-pulse double electron-electron resonance (DEER) experiment where neither method is particularly reliable. The work presented here utilizes L-band (1.9 GHz) in combination with non-adiabatic rapid sweep (NARS) EPR to address this opportunity by increasing the upper limit of the CW technique. Because L-band linewidths are three to seven times narrower than those at X-band, dipolar broadenings that are small relative to the X-band inhomogeneous linewidth become observable, but the signal loss, due to the frequency dependence of the Boltzmann factor, has made L-band especially challenging. NARS has been shown to increase sensitivity by a factor of five, and overcomes much of this loss, making L-band distance determination more feasible. Two different systems are presented, and distances of 18-30 Å have been experimentally determined at physiologically relevant temperatures. Measurements are in excellent agreement with a helical model and values determined by DEER.
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Affiliation(s)
- Aaron W. Kittell
- National Biomedical EPR Center, Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Eric J. Hustedt
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - James S. Hyde
- National Biomedical EPR Center, Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
- Corresponding author: James S. Hyde, PhD, Professor of Biophysics, Director, National Biomedical EPR Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, Phone: 414-456-4005,
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23
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Wu S, Liu S, Sim S, Pedersen LG. Weakly Antiferromagentic Coupling Via Superexchange Interaction Between Mn(II)-Mn(II) Atoms: A QM/MM Study of the Active Site of Human Cytosolic X-Propyl Aminopeptidase P. J Phys Chem Lett 2012; 3:2293-2297. [PMID: 23145216 PMCID: PMC3491985 DOI: 10.1021/jz300768g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We investigate the dinuclear manganese, Mn(II)-Mn(II), active site of human cytosolic X-propyl aminopeptidase (XPNPEP1) employing the QM/MM method. The optimized structure supports two manganese atoms at the active site and excludes the possibility of a single Mn(II) atom or other combination of divalent metal ions: Ca(II), Fe(II), Mg(II). A broken symmetry solution verifies an antiferromagnetically coupled state between the Mn(II)-Mn(II) pair, which is the ground state. From the energy difference between the high spin state (HS) and the broken symmetry state (BS), we estimate the exchange coupling constant, J, to be 5.15 cm(-1). Also, we observe multiple bridges (p orbitals) from solvent and two carboxylate linking to the Mn(II)-Mn(II), which leads to the weakly antiferromagnetic interaction of d(5)-d(5) electrons through superexchange coupling.
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Affiliation(s)
- Sangwook Wu
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-329
| | - Shubin Liu
- Research Computing Center, University of North Carolina, Chapel Hill, North Carolina 27599-3420
| | - Sooyeon Sim
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-329
| | - Lee G. Pedersen
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-329
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Zamora PL, Villamena FA. Theoretical and experimental studies of the spin trapping of inorganic radicals by 5,5-dimethyl-1-pyrroline N-oxide (DMPO). 3. Sulfur dioxide, sulfite, and sulfate radical anions. J Phys Chem A 2012; 116:7210-8. [PMID: 22668066 PMCID: PMC3428032 DOI: 10.1021/jp3039169] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Radical forms of sulfur dioxide (SO(2)), sulfite (SO(3)(2-)), sulfate (SO(4)(2-)), and their conjugate acids are known to be generated in vivo through various chemical and biochemical pathways. Oxides of sulfur are environmentally pervasive compounds and are associated with a number of health problems. There is growing evidence that their toxicity may be mediated by their radical forms. Electron paramagnetic resonance (EPR) spin trapping using the commonly used spin trap, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), has been employed in the detection of SO(3)(•-) and SO(4)(•-). The thermochemistries of SO(2)(•-), SO(3)(•-), SO(4)(•-), and their respective conjugate acids addition to DMPO were predicted using density functional theory (DFT) at the PCM/B3LYP/6-31+G**//B3LYP/6-31G* level. No spin adduct was observed for SO(2)(•-) by EPR, but an S-centered adduct was observed for SO(3)(•-)and an O-centered adduct for SO(4)(•-). Determination of adducts as S- or O-centered was made via comparison based on qualitative trends of experimental hfcc's with theoretical values. The thermodynamics of the nonradical addition of SO(3)(2-) and HSO(3)(-) to DMPO followed by conversion to the corresponding radical adduct via the Forrester-Hepburn mechanism was also calculated. Adduct acidities and decomposition pathways were investigated as well, including an EPR experiment using H(2)(17)O to determine the site of hydrolysis of O-centered adducts. The mode of radical addition to DMPO is predicted to be governed by several factors, including spin population density, and geometries stabilized by hydrogen bonds. The thermodynamic data supports evidence for the radical addition pathway over the nucleophilic addition mechanism.
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Affiliation(s)
- Pedro L. Zamora
- Department of Pharmacology, The Davis Heart and Lung Research Institute and Center for Biomedical EPR Spectroscopy and Imaging, College of Medicine, The Ohio State University, Columbus, Ohio, USA 43210
| | - Frederick A. Villamena
- Department of Pharmacology, The Davis Heart and Lung Research Institute and Center for Biomedical EPR Spectroscopy and Imaging, College of Medicine, The Ohio State University, Columbus, Ohio, USA 43210
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Popova AM, Hatmal MM, Frushicheva M, Price EA, Qin PZ, Haworth IS. Nitroxide sensing of a DNA microenvironment: mechanistic insights from EPR spectroscopy and molecular dynamics simulations. J Phys Chem B 2012; 116:6387-96. [PMID: 22574834 PMCID: PMC3382087 DOI: 10.1021/jp303303v] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The behavior of the nitroxide spin labels 1-oxyl-4-bromo-2,2,5,5-tetramethylpyrroline (R5a) and 1-oxyl-2,2,5,5-tetramethylpyrroline (R5) attached at a phosphorothioate-substituted site in a DNA duplex is modulated by the DNA in a site- and stereospecific manner. A better understanding of the mechanisms of R5a/R5 sensing of the DNA microenvironment will enhance our capability to relate information from nitroxide spectra to sequence-dependent properties of DNA. Toward this goal, electron paramagnetic resonance (EPR) spectroscopy and molecular dynamics (MD) simulations were used to investigate R5 and R5a attached as R(p) and S(p) diastereomers at phosphorothioate (pS)C(7) of d(CTACTG(pS)C(7)Y(8)TTAG). d(CTAAAGCAGTAG) (Y = T or U). X-band continuous-wave EPR spectra revealed that the dT(8) to dU(8) change alters nanosecond rotational motions of R(p)-R5a but produces no detectable differences for S(p)-R5a, R(p)-R5, and S(p)-R5. MD simulations were able to qualitatively account for these spectral variations and provide a plausible physical basis for the R5/R5a behavior. The simulations also revealed a correlation between DNA backbone B(I)/B(II) conformations and R5/R5a rotational diffusion, thus suggesting a direct connection between DNA local backbone dynamics and EPR-detectable R5/R5a motion. These results advance our understanding of how a DNA microenvironment influences nitroxide motion and the observed EPR spectra. This may enable use of R5/R5a for a quantitative description of the sequence-dependent properties of large biologically relevant DNA molecules.
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Affiliation(s)
- Anna M. Popova
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0744
| | - Ma’mon M. Hatmal
- Department of Biochemistry, University of Southern California, Los Angeles, California 90033-1039
| | - Maria Frushicheva
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0744
| | - Eric A. Price
- Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-0744
| | - Peter Z. Qin
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0744
| | - Ian S. Haworth
- Department of Biochemistry, University of Southern California, Los Angeles, California 90033-1039
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, California 90089-9121
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Ahmad R, Potter LC, Khramtsov VV. Spectral modeling for accelerated pH spectroscopy using EPR. J Magn Reson 2012; 218:86-92. [PMID: 22578559 PMCID: PMC3351691 DOI: 10.1016/j.jmr.2012.03.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Revised: 03/01/2012] [Accepted: 03/02/2012] [Indexed: 05/31/2023]
Abstract
A data modeling and processing method for electron paramagnetic resonance (EPR)-based pH spectroscopy is presented. The proposed method models the EPR spectrum of a pH-sensitive probe in both protonated and unprotonated forms. Under slow-exchange conditions, the EPR spectrum of a sample with an unknown pH value can be accurately represented by a weighted sum of the two models, with the pH value completely determined by their relative weights. Unlike traditional pH spectroscopy, which relies on locating resonance peaks, the proposed modeling-based approach utilizes the information from the entire scan and hence leads to more accurate estimation of pH for a given acquisition time. By employing the proposed methodology, we expect a reduction in the pH estimation error by more than a factor of three, which represents an order of magnitude reduction in acquisition time compared to the traditional method.
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Affiliation(s)
- R Ahmad
- Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA.
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Subczynski WK, Wisniewska A, Widomska J. Can macular xanthophylls replace cholesterol in formation of the liquid-ordered phase in lipid-bilayer membranes? Acta Biochim Pol 2012; 59:109-114. [PMID: 22428142 PMCID: PMC3963429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 03/01/2012] [Indexed: 05/31/2023]
Abstract
Lateral organization of membranes made from binary mixtures of dimyristoylphosphatidylcholine (DMPC) or dipalmitoylphosphatidylcholine (DPPC) and macular xanthophylls (lutein or zeaxanthin) was investigated using the saturation-recovery (SR) EPR spin-labeling discrimination by oxygen transport (DOT) method in which the bimolecular collision rate of molecular oxygen with the nitroxide spin label is measured. This work was undertaken to examine whether or not lutein and zeaxanthin, macular xanthophylls that parallel cholesterol in its function as a regulator of both membrane fluidity and hydrophobicity, can parallel other structural functions of cholesterol, including formation of the liquid-ordered phase in membranes. The DOT method permits discrimination of different membrane phases when the collision rates (oxygen transport parameter) differ in these phases. Additionally, membrane phases can be characterized by the oxygen transport parameter in situ without the need for separation, which provides information about the dynamics of each phase. In gel-phase membranes, two coexisting phases were discriminated in the presence of macular xanthophylls - namely, the liquid-ordered-like and solid-ordered-like phases. However, in fluid-phase membranes, xanthophylls only induce the solitary liquid-ordered-like phase, while at similar concentrations, cholesterol induces coexisting liquid-ordered and liquid-disordered phases. No significant differences between the effects of lutein and zeaxanthin were found.
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Affiliation(s)
| | - Anna Wisniewska
- Department of Biophysics, Faculty of Biochemistry, Biophysics, and Biotechnology, Jagiellonian University, Krakow, Poland
| | - Justyna Widomska
- Department of Biophysics, Medical University of Lublin, Lublin, Poland
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Ahmad R, Som S, Johnson DH, Zweier JL, Kuppusamy P, Potter LC. Multisite EPR oximetry from multiple quadrature harmonics. J Magn Reson 2012; 214:135-143. [PMID: 22154283 PMCID: PMC3257390 DOI: 10.1016/j.jmr.2011.10.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Revised: 10/24/2011] [Accepted: 10/25/2011] [Indexed: 05/31/2023]
Abstract
Multisite continuous wave (CW) electron paramagnetic resonance (EPR) oximetry using multiple quadrature field modulation harmonics is presented. First, a recently developed digital receiver is used to extract multiple harmonics of field modulated projection data. Second, a forward model is presented that relates the projection data to unknown parameters, including linewidth at each site. Third, a maximum likelihood estimator of unknown parameters is reported using an iterative algorithm capable of jointly processing multiple quadrature harmonics. The data modeling and processing are applicable for parametric lineshapes under nonsaturating conditions. Joint processing of multiple harmonics leads to 2-3-fold acceleration of EPR data acquisition. For demonstration in two spatial dimensions, both simulations and phantom studies on an L-band system are reported.
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Affiliation(s)
- R Ahmad
- Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA.
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29
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Crayton SH, Tsourkas A. pH-titratable superparamagnetic iron oxide for improved nanoparticle accumulation in acidic tumor microenvironments. ACS Nano 2011; 5:9592-601. [PMID: 22035454 PMCID: PMC3246562 DOI: 10.1021/nn202863x] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
A wide variety of nanoparticle platforms are being developed for the diagnosis and treatment of malignancy. While many of these are passively targeted or rely on receptor-ligand interactions, metabolically directed nanoparticles provide a complementary approach. It is known that both primary and secondary events in tumorigenesis alter the metabolic profile of developing and metastatic cancers. One highly conserved metabolic phenotype is a state of up-regulated glycolysis and reduced use of oxidative phosphorylation, even when oxygen tension is not limiting. This metabolic shift, termed the Warburg effect, creates a "hostile" tumor microenvironment with increased levels of lactic acid and low extracellular pH. In order to exploit this phenomenon and improve the delivery of nanoparticle platforms to a wide variety of tumors, a pH-responsive iron oxide nanoparticle was designed. Specifically, glycol chitosan (GC), a water-soluble polymer with pH-titratable charge, was conjugated to the surface of superparamagnetic iron oxide nanoparticles (SPIO) to generate a T(2)*-weighted MR contrast agent that responds to alterations in its surrounding pH. Compared to control nanoparticles that lack pH sensitivity, these GC-SPIO nanoparticles demonstrated potent pH-dependent cellular association and MR contrast in vitro. In murine tumor models, GC-SPIO also generated robust T(2)*-weighted contrast, which correlated with increased delivery of the agent to the tumor site, measured quantitatively by inductively coupled plasma mass spectrometry. Importantly, the increased delivery of GC-SPIO nanoparticles cannot be solely attributed to the commonly observed enhanced permeability and retention effect since these nanoparticles have similar physical properties and blood circulation times as control agents.
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Affiliation(s)
| | - Andrew Tsourkas
- Corresponding Author: Dr. Andrew Tsourkas, 210 S. 33rd Street, 240 Skirkanich Hall, Philadelphia, PA 19104, Phone: 215-898-8167, Fax: 215-573-2071,
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Mainali L, Raguz M, Camenisch TG, Hyde JS, Subczynski WK. Spin-label saturation-recovery EPR at W-band: applications to eye lens lipid membranes. J Magn Reson 2011; 212:86-94. [PMID: 21745756 PMCID: PMC3163743 DOI: 10.1016/j.jmr.2011.06.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 06/15/2011] [Accepted: 06/16/2011] [Indexed: 05/03/2023]
Abstract
Saturation-recovery (SR) EPR at W-band (94 GHz) to obtain profiles of the membrane fluidity and profiles of the oxygen transport parameter is demonstrated for lens lipid membranes using phosphatidylcholine (n-PC), stearic acid (n-SASL), and cholesterol analog (ASL and CSL) spin labels, and compared with results obtained in parallel experiments at X-band (9.4 GHz). Membranes were derived from the total lipids extracted from 2-year-old porcine lens cortex and nucleus. Two findings are especially significant. First, measurements of the spin-lattice relaxation times T1 for n-PCs allowed T1 profiles across the membrane to be obtained. These profiles reflect local membrane properties differently than profiles of the order parameter. Profiles obtained at W-band are, however, shifted to longer T1 values compared to those obtained at X-band. Second, using cholesterol analog spin labels and relaxation agents (hydrophobic oxygen and water-soluble NiEDDA), the cholesterol bilayer domain was discriminated in membranes made from lipids of the lens nucleus. However, membranes made from cortical lipids show a single homogeneous environment. Profiles of the oxygen transport parameter obtained from W-band measurements are practically identical to those obtained from X-band measurements, and are very similar to those obtained earlier at X-band for membranes made of 2-year-old bovine cortical and nuclear lens lipids (M. Raguz, J. Widomska, J. Dillon, E.R. Gaillard, W.K. Subczynski, Biochim. Biophys. Acta 1788 (2009) 2380-2388). Results demonstrate that SR EPR at W-band has the potential to be a powerful tool for studying samples of small volume, ∼30 nL, compared with the sample volume of ∼3 μL at X-band.
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Affiliation(s)
- Laxman Mainali
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Marija Raguz
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
- Department of Medical Physics and Biophysics, School of Medicine, University of Split, Split, Croatia
| | | | - James S. Hyde
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Witold K. Subczynski
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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31
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Khan N, Blinco JP, Bottle SE, Hosokawa K, Swartz HM, Micallef AS. The evaluation of new and isotopically labeled isoindoline nitroxides and an azaphenalene nitroxide for EPR oximetry. J Magn Reson 2011; 211:170-7. [PMID: 21665499 PMCID: PMC3143274 DOI: 10.1016/j.jmr.2011.05.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 05/14/2011] [Accepted: 05/14/2011] [Indexed: 05/26/2023]
Abstract
Isoindoline nitroxides are potentially useful probes for viable biological systems, exhibiting low cytotoxicity, moderate rates of biological reduction and favorable Electron Paramagnetic Resonance (EPR) characteristics. We have evaluated the anionic (5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl; CTMIO), cationic (5-(N,N,N-trimethylammonio)-1,1,3,3-tetramethylisoindolin-2-yloxyl iodide, QATMIO) and neutral (1,1,3,3-tetramethylisoindolin-2-yloxyl; TMIO) nitroxides and their isotopically labeled analogs ((2)H(12)- and/or (2)H(12)-(15)N-labeled) as potential EPR oximetry probes. An active ester analogue of CTMIO, designed to localize intracellularly, and the azaphenalene nitroxide 1,1,3,3-tetramethyl-2,3-dihydro-2-azaphenalen-2-yloxyl (TMAO) were also studied. While the EPR spectra of the unlabeled nitroxides exhibit high sensitivity to O(2) concentration, deuteration resulted in a loss of superhyperfine features and a subsequent reduction in O(2) sensitivity. Labeling the nitroxides with (15)N increased the signal intensity and this may be useful in decreasing the detection limits for in vivo measurements. The active ester nitroxide showed approximately 6% intracellular localization and low cytotoxicity. The EPR spectra of TMAO nitroxide indicated an increased rigidity in the nitroxide ring, due to dibenzo-annulation.
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Affiliation(s)
- Nadeem Khan
- EPR Centre for Viable Systems, Department of Radiology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
| | - James P. Blinco
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, Faculty of Science and Technology, Queensland University of Technology, Brisbane, Queensland 4001, Australia
| | - Steven E. Bottle
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, Faculty of Science and Technology, Queensland University of Technology, Brisbane, Queensland 4001, Australia
| | - Kazuyuki Hosokawa
- ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, Faculty of Science and Technology, Queensland University of Technology, Brisbane, Queensland 4001, Australia
| | - Harold M. Swartz
- EPR Centre for Viable Systems, Department of Radiology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
| | - Aaron S. Micallef
- Australian Institute for Bioengineering and Nanotechnology and School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, Queensland 4072, Australia
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Tseitlin M, Quine RW, Eaton SS, Eaton GR. Use of polyphase continuous excitation based on the Frank sequence in EPR. J Magn Reson 2011; 211:221-7. [PMID: 21737326 PMCID: PMC3148075 DOI: 10.1016/j.jmr.2011.06.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Revised: 05/14/2011] [Accepted: 06/06/2011] [Indexed: 05/12/2023]
Abstract
Polyphase continuous excitation based on the Frank sequence is suggested as an alternative to single pulse excitation in EPR. The method allows reduction of the source power, while preserving the excitation bandwidth of a single pulse. For practical EPR implementation the use of a cross-loop resonator is essential to provide isolation between the spin system and the resonator responses to the excitation. Provided that a line broadening of about 5% is acceptable, the cumulative turning angle of the magnetization vector generated by the excitation sequence can be quite large and can produce signal amplitudes that are comparable to that achieved with a higher power 90° pulse.
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Affiliation(s)
- Mark Tseitlin
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208
| | - Richard W. Quine
- School of Engineering and Computer Science, University of Denver, Denver, CO 80208
| | - Sandra S. Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208
| | - Gareth R. Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208
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Velayutham M, Hemann C, Zweier JL. Removal of H₂O₂ and generation of superoxide radical: role of cytochrome c and NADH. Free Radic Biol Med 2011; 51:160-70. [PMID: 21545835 PMCID: PMC3112007 DOI: 10.1016/j.freeradbiomed.2011.04.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Revised: 03/10/2011] [Accepted: 04/04/2011] [Indexed: 11/20/2022]
Abstract
In cells, mitochondria, endoplasmic reticulum, and peroxisomes are the major sources of reactive oxygen species (ROS) under physiological and pathophysiological conditions. Cytochrome c (cyt c) is known to participate in mitochondrial electron transport and has antioxidant and peroxidase activities. Under oxidative or nitrative stress, the peroxidase activity of Fe³⁺cyt c is increased. The level of NADH is also increased under pathophysiological conditions such as ischemia and diabetes and a concurrent increase in hydrogen peroxide (H₂O₂) production occurs. Studies were performed to understand the related mechanisms of radical generation and NADH oxidation by Fe³⁺cyt c in the presence of H₂O₂. Electron paramagnetic resonance (EPR) spin trapping studies using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) were performed with NADH, Fe³⁺cyt c, and H₂O₂ in the presence of methyl-β-cyclodextrin. An EPR spectrum corresponding to the superoxide radical adduct of DMPO encapsulated in methyl-β-cyclodextrin was obtained. This EPR signal was quenched by the addition of the superoxide scavenging enzyme Cu,Zn-superoxide dismutase (SOD1). The amount of superoxide radical adduct formed from the oxidation of NADH by the peroxidase activity of Fe³⁺cyt c increased with NADH and H₂O₂ concentration. From these results, we propose a mechanism in which the peroxidase activity of Fe³⁺cyt c oxidizes NADH to NAD(•), which in turn donates an electron to O₂, resulting in superoxide radical formation. A UV-visible spectroscopic study shows that Fe³⁺cyt c is reduced in the presence of both NADH and H₂O₂. Our results suggest that Fe³⁺cyt c could have a novel role in the deleterious effects of ischemia/reperfusion and diabetes due to increased production of superoxide radical. In addition, Fe³⁺cyt c may play a key role in the mitochondrial "ROS-induced ROS-release" signaling and in mitochondrial and cellular injury/death. The increased oxidation of NADH and generation of superoxide radical by this mechanism may have implications for the regulation of apoptotic cell death, endothelial dysfunction, and neurological diseases. We also propose an alternative electron transfer pathway, which may protect mitochondria and mitochondrial proteins from oxidative damage.
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Affiliation(s)
- Murugesan Velayutham
- Address correspondence to: Murugesan Velayutham, Ph.D, TMRF, Room 130, 420, W. 12th Avenue, The Ohio State University, Columbus, OH - 43210, Phone: 614-292-9082, Fax: 614-292-8454, , Jay L. Zweier, MD, Davis Heart and Lung Research Institute, 473 W. 12th Ave, Room 611C, The Ohio State University, Columbus, OH - 43210, Phone: 614-247-7788, Fax: 614-292-8778,
| | | | - Jay L. Zweier
- Address correspondence to: Murugesan Velayutham, Ph.D, TMRF, Room 130, 420, W. 12th Avenue, The Ohio State University, Columbus, OH - 43210, Phone: 614-292-9082, Fax: 614-292-8454, , Jay L. Zweier, MD, Davis Heart and Lung Research Institute, 473 W. 12th Ave, Room 611C, The Ohio State University, Columbus, OH - 43210, Phone: 614-247-7788, Fax: 614-292-8778,
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Raguz M, Mainali L, Widomska J, Subczynski WK. The immiscible cholesterol bilayer domain exists as an integral part of phospholipid bilayer membranes. Biochim Biophys Acta 2011; 1808:1072-80. [PMID: 21192917 PMCID: PMC3062709 DOI: 10.1016/j.bbamem.2010.12.019] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 12/15/2010] [Accepted: 12/16/2010] [Indexed: 11/18/2022]
Abstract
Electron paramagnetic resonance (EPR) spin-labeling methods were used to study the organization of cholesterol and phospholipids in membranes formed from Chol/POPS (cholesterol/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylserine) mixtures, with mixing ratios from 0 to 3. It was confirmed using the discrimination by oxygen transport and polar relaxation agent accessibility methods that the immiscible cholesterol bilayer domain (CBD) was present in all of the suspensions when the mixing ratio exceeded the cholesterol solubility threshold (CST) in the POPS membrane. The behavior of phospholipid molecules was monitored with phospholipid analogue spin labels (n-PCs), and the behavior of cholesterol was monitored with the cholesterol analogue spin labels CSL and ASL. Results indicated that phospholipid and cholesterol mixtures can form a membrane suspension up to a mixing ratio of ~2. Additionally, EPR spectra for n-PC, ASL, and CSL indicated that both phospholipids and cholesterol exist in these suspensions in the lipid-bilayer-like structures. EPR spectral characteristics of n-PCs (spin labels located in the phospholipid cholesterol bilayer, outside the CBD) change with increase in the cholesterol content up to and beyond the CST. These results present strong evidence that the CBD forms an integral part of the phospholipid bilayer when formed from a Chol/POPS mixture up to a mixing ratio of ~2. Interestingly, CSL in cholesterol alone (without phospholipids) when suspended in buffer does not detect formation of bilayer-like structures. A broad, single-line EPR signal is given, similar to that obtained for the dry film of cholesterol before addition of the buffer. This broad, single-line signal is also observed in suspensions formed for Chol/POPS mixtures (as a background signal) when the Chol/POPS ratio is much greater than 3. It is suggested that the EPR spin-labeling approach can discriminate and characterize the fraction of cholesterol that forms the CBD within the phospholipid bilayer.
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Affiliation(s)
- Marija Raguz
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
- Department of Medical Physics and Biophysics, School of Medicine, University of Split, Split, Croatia
| | - Laxman Mainali
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | | | - Witold K. Subczynski
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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Palmer J, Potter L, Ahmad R. Optimization of magnetic field sweep and field modulation amplitude for continuous-wave EPR oximetry. J Magn Reson 2011; 209:337-340. [PMID: 21334232 PMCID: PMC3086786 DOI: 10.1016/j.jmr.2011.01.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Revised: 11/22/2010] [Accepted: 01/10/2011] [Indexed: 05/30/2023]
Abstract
For continuous-wave electron paramagnetic resonance spectroscopy, what settings of magnetic field sweep width and field modulation amplitude yield the best accuracy in estimated linewidth? Statistical bounds on estimation error presented in this work provide practical guidance: set the sweep width and modulation amplitude to 8 and 4 times the half-width half-maximum linewidth, Γ, respectively. For unknown linewidths in the range [Γ(min),Γ(max)] the worst-case estimation error is minimized by using settings designed for Γ(max). The analysis assumes a Lorentzian lineshape and a constant modulation amplitude across the extent of the irradiated paramagnetic probe. The analytical guidelines are validated using L-band spectroscopy with a particulate LiNc-BuO probe.
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Affiliation(s)
- J. Palmer
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - L.C. Potter
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - R. Ahmad
- Center of Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
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Tseitlin M, Quine RW, Eaton SS, Eaton GR, Halpern HJ, Ardenkjaer-Larsen JH. Use of the Frank sequence in pulsed EPR. J Magn Reson 2011; 209:306-9. [PMID: 21371924 PMCID: PMC3107679 DOI: 10.1016/j.jmr.2011.01.032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 01/28/2011] [Accepted: 01/28/2011] [Indexed: 05/12/2023]
Abstract
The Frank polyphase sequence has been applied to pulsed EPR of triarylmethyl radicals at 25 6 MHz (9.1 mT magnetic field), using 256 phase pulses. In EPR, as in NMR, use of a Frank sequence of phase steps permits pulsed FID signal acquisition with very low power microwave/RF pulses (ca. 1.5 mW in the application reported here) relative to standard pulsed EPR. A 0.2 mM aqueous solution of a triarylmethyl radical was studied using a 16 mm diameter cross-loop resonator to isolate the EPR signal detection system from the incident pulses.
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Affiliation(s)
- Mark Tseitlin
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208
| | - Richard W. Quine
- School of Engineering and Computer Science, University of Denver, Denver, CO 80208
| | - Sandra S. Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208
| | - Gareth R. Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208
| | - Howard J. Halpern
- University of Chicago, Department of Radiation and Cellular Oncology, and University of Chicago Medical Center, 5835 S. Cottage Grove, Chicago, IL 60637, USA
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Ahmad R, Som S, Kesselring E, Kuppusamy P, Zweier JL, Potter LC. Digital detection and processing of multiple quadrature harmonics for EPR spectroscopy. J Magn Reson 2010; 207:322-31. [PMID: 20971667 PMCID: PMC2993834 DOI: 10.1016/j.jmr.2010.09.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 09/24/2010] [Accepted: 09/24/2010] [Indexed: 05/12/2023]
Abstract
A quadrature digital receiver and associated signal estimation procedure are reported for L-band electron paramagnetic resonance (EPR) spectroscopy. The approach provides simultaneous acquisition and joint processing of multiple harmonics in both in-phase and out-of-phase channels. The digital receiver, based on a high-speed dual-channel analog-to-digital converter, allows direct digital down-conversion with heterodyne processing using digital capture of the microwave reference signal. Thus, the receiver avoids noise and nonlinearity associated with analog mixers. Also, the architecture allows for low-Q anti-alias filtering and does not require the sampling frequency to be time-locked to the microwave reference. A noise model applicable for arbitrary contributions of oscillator phase noise is presented, and a corresponding maximum-likelihood estimator of unknown parameters is also reported. The signal processing is applicable for Lorentzian lineshape under nonsaturating conditions. The estimation is carried out using a convergent iterative algorithm capable of jointly processing the in-phase and out-of-phase data in the presence of phase noise and unknown microwave phase. Cramér-Rao bound analysis and simulation results demonstrate a significant reduction in linewidth estimation error using quadrature detection, for both low and high values of phase noise. EPR spectroscopic data are also reported for illustration.
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Affiliation(s)
- R Ahmad
- Center of Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA.
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Zhang X, Lee SW, Zhao L, Xia T, Qin PZ. Conformational distributions at the N-peptide/boxB RNA interface studied using site-directed spin labeling. RNA 2010; 16:2474-2483. [PMID: 20980674 PMCID: PMC2995408 DOI: 10.1261/rna.2360610] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Accepted: 09/11/2010] [Indexed: 05/30/2023]
Abstract
In bacteriophage λ, interactions between a 22-amino acid peptide (called the N-peptide) and a stem-loop RNA element (called boxB) play a critical role in transcription anti-termination. The N-peptide/boxB complex has been extensively studied, and serves as a paradigm for understanding mechanisms of protein/RNA recognition. Particularly, ultrafast spectroscopy techniques have been applied to monitor picosecond fluorescence decay behaviors of 2-aminopurines embedded at various positions of the boxB RNA. The studies have led to a model in which the bound N-peptide exists in dynamic equilibrium between two states, with peptide C-terminal fragment either stacking on (i.e., the stacked state) or peeling away from (i.e., the unstacked state) the RNA loop. The function of the N-peptide/boxB complex seems to correlate with the fraction of the stacked state. Here, the N-peptide/boxB system is studied using the site-directed spin labeling technique, in which X-band electron paramagnetic resonance spectroscopy is applied to monitor nanosecond rotational behaviors of stable nitroxide radicals covalently attached to different positions of the N-peptide. The data reveal that in the nanosecond regime the C-terminal fragment of bound N-peptide adopts multiple discrete conformations within the complex. The characteristics of these conformations are consistent with the proposed stacked and unstacked states, and their distributions vary upon mutations within the N-peptide. These results suggest that the dynamic two-state model remains valid in the nanosecond regime, and represents a unique mode of function in the N-peptide/boxB RNA complex. It also demonstrates a connection between picosecond and nanosecond dynamics in a biological complex.
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Affiliation(s)
- Xiaojun Zhang
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0744, USA
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Ward R, Bowman A, Sozudogru E, El-Mkami H, Owen-Hughes T, Norman DG. EPR distance measurements in deuterated proteins. J Magn Reson 2010; 207:164-7. [PMID: 20805036 PMCID: PMC3516800 DOI: 10.1016/j.jmr.2010.08.002] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 07/09/2010] [Accepted: 08/06/2010] [Indexed: 05/02/2023]
Abstract
One of the major problems facing distance determination by pulsed EPR, on spin-labeled proteins, has been the short relaxation time T(m). Solvent deuteration has previously been used to slow relaxation and so extend the range of distance measurement and sensitivity. We demonstrate here that deuteration of the underlying protein, as well as the solvent, extends the T(m) to a considerable degree. Longer T(m) gives greatly enhanced sensitivity, much extended distance measurement, more reliable distance distribution calculation and better baseline correction.
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Affiliation(s)
- Richard Ward
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Andrew Bowman
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Erman Sozudogru
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | | | - Tom Owen-Hughes
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - David G. Norman
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
- Corresponding author. Fax: +44(0)1382 386373
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Ahmad R, Caia G, Potter L, Petryakov S, Kuppusamy P, Zweier J. In vivo multisite oximetry using EPR-NMR coimaging. J Magn Reson 2010; 207:69-77. [PMID: 20850361 PMCID: PMC2956866 DOI: 10.1016/j.jmr.2010.08.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 05/19/2010] [Accepted: 08/17/2010] [Indexed: 05/29/2023]
Abstract
Coimaging employing electron paramagnetic resonance (EPR) imaging and MRI is used for rapid in vivo oximetry conducted simultaneously across multiple organs of a mouse. A recently developed hybrid EPR-NMR coimaging instrument is used for both EPR and NMR measurements. Oxygen sensitive particulate EPR probe is implanted in small localized pockets, called sites, across multiple regions of a live mouse. Three dimensional MRI is used to generate anatomic visualization, providing precise locations of implant sites. The pO₂ values, one for every site, are then estimated from EPR measurements. To account for radio frequency (RF) phase inhomogeneities inside a large resonator carrying a lossy sample, a generalization of an existing EPR data model is proposed. Utilization of known spectral lineshape, sparse distribution, and known site locations reduce the EPR data collection by more than an order of magnitude over a conventional spectral-spatial imaging, enhancing the feasibility of in vivo EPR oximetry for clinically relevant models.
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Affiliation(s)
- R. Ahmad
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, OH, 43210, USA
| | - G. Caia
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, OH, 43210, USA
| | - L.C. Potter
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - S. Petryakov
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, OH, 43210, USA
| | - P. Kuppusamy
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, OH, 43210, USA
| | - J.L. Zweier
- Center for Biomedical EPR Spectroscopy and Imaging, Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, OH, 43210, USA
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Quine RW, Rinard GA, Eaton SS, Eaton GR. Quantitative rapid scan EPR spectroscopy at 258 MHz. J Magn Reson 2010; 205:23-7. [PMID: 20382055 PMCID: PMC3097513 DOI: 10.1016/j.jmr.2010.03.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2009] [Revised: 03/17/2010] [Accepted: 03/18/2010] [Indexed: 05/05/2023]
Abstract
Experimental data obtained with an electron paramagnetic resonance (EPR) rapid scan spectrometer were translated through the reverse transfer functions of the spectrometer hardware to the sample position. Separately, theoretical calculations were performed to predict signal and noise amplitudes at the sample position for specified experimental conditions. A comparison was then made between the translated experimental values and the calculated values. Excellent agreement was obtained.
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Affiliation(s)
| | | | - Sandra S. Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208
| | - Gareth R. Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208
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Meenakshisundaram G, Eteshola E, Blank A, Lee SC, Kuppusamy P. A molecular paramagnetic spin-doped biopolymeric oxygen sensor. Biosens Bioelectron 2010; 25:2283-9. [PMID: 20371170 PMCID: PMC2866758 DOI: 10.1016/j.bios.2010.03.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2009] [Revised: 03/01/2010] [Accepted: 03/08/2010] [Indexed: 11/15/2022]
Abstract
Electron paramagnetic resonance (EPR) oximetry is a powerful technique capable of providing accurate, reliable, and repeated measurements of tissue oxygenation, which is crucial to the diagnosis and treatment of several pathophysiological conditions. Measurement of tissue pO(2) by EPR involves the use of paramagnetic, oxygen-sensitive probes, which can be either soluble (molecular) in nature or insoluble paramagnetic materials. Development of innovative strategies to enhance the biocompatibility and in vivo application of these oxygen-sensing probes is crucial to the growth and clinical applicability of EPR oximetry. Recent research efforts have aimed at encapsulating particulate probes in bioinert polymers for the development of biocompatible EPR probes. In this study, we have developed novel EPR oximetry probes, called perchlorotriphenylmethyl triester (PTM-TE):polydimethyl siloxane (PDMS) chips, by dissolving and incorporating the soluble (molecular) EPR probe, PTM-TE, in an oxygen-permeable polymer matrix, PDMS. We demonstrate that such incorporation (doping) of PTM-TE in PDMS enhanced its oxygen sensitivity several fold. The cast-molding method of fabricating chips enabled them to be made with increasing amounts of PTM-TE (spin density). Characterization of the spin distribution within the PDMS matrix, using EPR micro-imaging, revealed potential inhomogeneties, albeit with no adverse effect on the oxygen-sensing characteristics of PTM-TE:PDMS. The chips were resistant to autoclaving or in vitro oxidoreductant treatment, thus exhibiting excellent in vitro biostability. Our results establish PTM-TE:PDMS as a viable probe for biological oxygen-sensing, and also validate the incorporation of soluble probes in polymer matrices as an innovative approach to the development of novel probes for EPR oximetry.
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Affiliation(s)
- Guruguhan Meenakshisundaram
- Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
- Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
| | - Edward Eteshola
- Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - Aharon Blank
- Schulich Faculty of Chemistry, Technion - Israel Institute of Technology, Haifa, 32000, Israel
| | - Stephen C. Lee
- Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - Periannan Kuppusamy
- Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
- Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
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Samuni Y, Ishii H, Hyodo F, Samuni U, Krishna MC, Goldstein S, Mitchell JB. Reactive oxygen species mediate hepatotoxicity induced by the Hsp90 inhibitor geldanamycin and its analogs. Free Radic Biol Med 2010; 48:1559-63. [PMID: 20211249 PMCID: PMC2862863 DOI: 10.1016/j.freeradbiomed.2010.03.001] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 02/24/2010] [Accepted: 03/01/2010] [Indexed: 11/19/2022]
Abstract
Geldanamycin (GM), a benzoquinone ansamycin antibiotic, is a natural product inhibitor of Hsp90 with potent and broad anti-cancer properties. Because of its adverse effects on liver, its less toxic derivatives 17-(allylamino)-17-demethoxygeldanamycin (17-AAG) and 17-(dimethylaminoethylamino)-17-demethoxygeldanamycin (17-DMAG) are currently being evaluated for the treatment of cancer. Previously, it has been demonstrated that the redox cycling of GM by NADPH-cytochrome P450 reductase leads to the formation of the GM semiquinone and superoxide radicals, the latter being identified using spin-trapping. We hypothesized that the different hepatotoxicity induced by GM, 17-AAG and 17-DMAG reflects the redox active properties of the quinone moiety and possibly the extent of superoxide formation, which may stimulate cellular oxidative injury. Our data demonstrate that superoxide can be efficiently trapped during the reduction of GM, 17-AAG and 17-DMAG by NADPH-cytochrome P450 reductase, and that superoxide formation rate followed the order 17-DMAG > 17-AAG > GM. In the absence of superoxide scavengers, the rate of NADPH oxidation followed the order 17-DMAG > GM > 17-AAG. The half-wave one-electron reduction potentials (E(1/2)) of GM, 17-AAG and 17-DMAG in DMSO have been determined to be -0.37, -0.13 and -0.015V (vs. Ag/AgCl), respectively. If the same order of E(1/2) follows in neutral aqueous media, thermodynamic considerations imply that 17-DMAG is more readily reduced by the P450 reductase as well as by superoxide. The order of the drug cytotoxicity toward rat primary hepatocytes, as determined by their effect on cell viability and on intracellular oxidant level, was opposite to the order of E(1/2) of the respective quinone/semiquinone couples. These results suggest that hepatotoxicity exhibited by the Hsp90 inhibitors belonging to benzoquinone ansamycins could be attributed to superoxide. The apparent discrepancy between the order of toxicity and the orders of superoxide formation rate, which is correlated with E(1/2), is discussed.
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Affiliation(s)
- Yuval Samuni
- Radiation Biology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Hisanari Ishii
- Radiation Biology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Fuminori Hyodo
- Radiation Biology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Uri Samuni
- Chemistry & Biochemistry Dep. Queens College, City University of New York, Flushing, NY 11367, USA
| | - Murali C. Krishna
- Radiation Biology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
- Correspondence: Murali C. Krishna, Radiation Biology Branch, Center for Cancer Research, NCI, NIH, Bethesda, MD 20892, , Phone: 301-451-6752, Fax: 301-480-2238
| | - Sara Goldstein
- Institute of Chemistry, The Accelerator Laboratory, the Hebrew University of Jerusalem, Jerusalem 91904, ISRAEL
| | - James B. Mitchell
- Radiation Biology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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Stoian SA, Paraschiv C, Kiritsakas N, Lloret F, Münck E, Bominaar EL, Andruh M. Mössbauer, electron paramagnetic resonance, and magnetic susceptibility studies on members of a new family of cyano-bridged 3d-4f complexes. Demonstration of anisotropic exchange in a Fe-Gd complex. Inorg Chem 2010; 49:3387-401. [PMID: 20225831 PMCID: PMC2856468 DOI: 10.1021/ic902516r] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The synthesis and crystallographic characterization of a new family of M(mu-CN)Ln complexes are reported. Two structural series have been prepared by reacting in water rare earth nitrates (Ln(III) = La, Pr, Nd, Sm, Eu, Gd, Dy, Ho) with K(3)[M(CN)(6)] (M(III) = Fe, Co) in the presence of hexamethylenetetramine (hmt). The first series consists of six isomorphous heterobinuclear complexes, [(CN)(5)M-CN-Ln(H(2)O)(8)].2hmt ([FeLa] 1, [FePr] 2, [FeNd] 3, [FeSm] 4, [FeEu] 5, [FeGd] 6), while the second series consists of four isostructural ionic complexes, [M(CN)(6)][Ln(H(2)O)(8)].hmt ([FeDy] 7, [FeHo] 8, [CoEu] 9, [CoGd] 10). The hexamethylenetetramine molecules contribute to the stabilization of the crystals by participating in an extended network of hydrogen bond interactions. In both series the aqua ligands are hydrogen bonded to the nitrogen atoms from both the terminal CN(-) groups and the hmt molecules. The [FeGd] complex has been analyzed with (57)Fe Mossbauer spectroscopy and magnetic susceptibility measurements. We have also analyzed the [FeLa] complex, in which the paramagnetic Gd(III) is replaced by diamagnetic La(III), with (57)Fe Mossbauer spectroscopy, electron paramagnetic resonance (EPR), and magnetic susceptibility measurements, to obtain information about the low-spin Fe(III) site that is not accessible in the presence of a paramagnetic ion at the complementary site. For the same reason, the [CoGd] complex, containing diamagnetic Co(III), was studied with EPR and magnetic susceptibility measurements, which confirmed the S = 7/2 spin of Gd(III). Prior knowledge about the paramagnetic sites in [FeGd] allows a detailed analysis of the exchange interactions between them. In particular, the question of whether the exchange interaction in [FeGd] is isotropic or anisotropic has been addressed. Standard variable-temperature magnetic susceptibility measurements provide only the value for a linear combination of J(x), J(y), and J(z) but contain no information about the values of the individual exchange parameters J(x), J(y), and J(z). In contrast, the spin-Hamiltonian analysis of the variable-field, variable-temperature Mossbauer spectra reveals an exquisite sensitivity on the anisotropic exchange parameters. Analysis of these dependencies in conjunction with adopting the g-values obtained for [FeLa], yielded the values J(x) = +0.11 cm(-1), J(y) = +0.33 cm(-1), and J(z) = +1.20 cm(-1) (S(1).J.S(2) convention). The consistency of these results with magnetic susceptibility data is analyzed. The exchange anisotropy is rooted in the spatial anisotropy of the low-spin Fe(III) ion. The condition for anisotropic exchange is the presence of low-lying orbital excited states at the ferric site that (i) effectively interact through spin-orbit coupling with the orbital ground state and (ii) have an exchange parameter with the Gd site with a value different from that for the ground state. Density functional theory (DFT) calculations, without spin-orbit coupling, reveal that the unpaired electron of the t(2g)(5) ground configuration of the Fe(III) ion occupies the xy orbital, that is, the orbital along the plane perpendicular to the Fe...Gd vector. The exchange-coupling constants for this orbital, j(xy), and for the other t(2g) orbitals, j(yz) and j(xz), have been determined using a theoretical model that relates them to the anisotropic exchange parameters and the g-values of Fe(III). The resulting values, j(yz) = -5.7 cm(-1), j(xz) = -4.9 cm(-1), and j(xy) = +0.3 cm(-1) are quite different. The origin of the difference is briefly discussed.
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Affiliation(s)
- Sebastian A. Stoian
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Ave., Pittsburgh, PA 15213
| | - Carmen Paraschiv
- Inorganic Chemistry Laboratory, Faculty of Chemistry, University of Bucharest, Str. Dumbrava Rosie nr. 23, 020464 Bucharest, Romania
| | - Nathalie Kiritsakas
- Laboratoire de Chimie de Coordination Organique, UMR CNRS 7140, Université Louis Pasteur, F-67000, Strasbourg, France
| | - Francesc Lloret
- Departamento de Química Inorgànica/Instituto de Ciencia Molecular (ICMoL), Universitat de València, Polígono La Coma s/n, 46980 Paterna, València, Spain
| | - Eckard Münck
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Ave., Pittsburgh, PA 15213
| | - Emile L. Bominaar
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Ave., Pittsburgh, PA 15213
| | - Marius Andruh
- Inorganic Chemistry Laboratory, Faculty of Chemistry, University of Bucharest, Str. Dumbrava Rosie nr. 23, 020464 Bucharest, Romania
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Crane JM, Lilly AA, Randall LL. Characterization of interactions between proteins using site-directed spin labeling and electron paramagnetic resonance spectroscopy. Methods Mol Biol 2010; 619:173-90. [PMID: 20419411 DOI: 10.1007/978-1-60327-412-8_11] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Site-directed spin-labeling and the analysis of proteins by electron paramagnetic resonance spectroscopy provides a powerful tool for identifying sites of contact within protein complexes at the resolution of aminoacyl side chains. Here we describe the method as we have used it to study interactions of proteins involved in export via the Sec secretory system in Escherichia coli. The method is amendable to the study of most protein interactions.
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Zoppellaro G, Bren KL, Ensign AA, Harbitz E, Kaur R, Hersleth HP, Ryde U, Hederstedt L, Andersson KK. Review: studies of ferric heme proteins with highly anisotropic/highly axial low spin (S = 1/2) electron paramagnetic resonance signals with bis-histidine and histidine-methionine axial iron coordination. Biopolymers 2009; 91:1064-82. [PMID: 19536822 PMCID: PMC2852197 DOI: 10.1002/bip.21267] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Six-coordinated heme groups are involved in a large variety of electron transfer reactions because of their ability to exist in both the ferrous (Fe(2+)) and ferric (Fe(3+)) state without any large differences in structure. Our studies on hemes coordinated by two histidines (bis-His) and hemes coordinated by histidine and methionine (His-Met) will be reviewed. In both of these coordination environments, the heme core can exhibit ferric low spin (electron paramagnetic resonance EPR) signals with large g(max) values (also called Type I, highly anisotropic low spin, or highly axial low spin, HALS species) as well as rhombic EPR (Type II) signals. In bis-His coordinated hemes rhombic and HALS envelopes are related to the orientation of the His groups with respect to each other such that (i) parallel His planes results in a rhombic signal and (ii) perpendicular His planes results in a HALS signal. Correlation between the structure of the heme and its ligands for heme with His-Met axial ligation and ligand-field parameters, as derived from a large series of cytochrome c variants, show, however, that for such a combination of axial ligands there is no clear-cut difference between the large g(max) and the "small g-anisotropy" cases as a result of the relative Met-His arrangements. Nonetheless, a new linear correlation links the average shift delta of the heme methyl groups with the g(max) values.
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Affiliation(s)
- Giorgio Zoppellaro
- Department of Molecular Biosciences, University of Oslo, PO Box 1041 Blindern, Oslo NO–0316, Norway
| | - Kara L. Bren
- Department of Chemistry, University of Rochester, Rochester, New York 146270216, USA
| | - Amy A. Ensign
- Department of Chemistry, University of Rochester, Rochester, New York 146270216, USA
| | - Espen Harbitz
- Department of Molecular Biosciences, University of Oslo, PO Box 1041 Blindern, Oslo NO–0316, Norway
| | - Ravinder Kaur
- Department of Chemistry, University of Rochester, Rochester, New York 146270216, USA
| | - Hans-Petter Hersleth
- Department of Molecular Biosciences, University of Oslo, PO Box 1041 Blindern, Oslo NO–0316, Norway
| | - Ulf Ryde
- Department Theoretical Chemistry, Lund University, Chemical Centre, P. O. Box 124, SE–221 00 Lund, Sweden
| | - Lars Hederstedt
- Department of Cell & Organism Biology, Lund University, Sölvegatan 35, SE–22362 Lund, Sweden
| | - K. Kristoffer Andersson
- Department of Molecular Biosciences, University of Oslo, PO Box 1041 Blindern, Oslo NO–0316, Norway
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Abstract
Electron paramagnetic resonance (EPR) and, more recently, solid-state nuclear magnetic resonance (NMR) have been employed to study photosynthetic processes, primarily related to the light-induced charge separation. Information obtained on the electronic structure, the relative orientation of the cofactors, and the changes in structure during these reactions should help to understand the efficiency of light-induced charge separation. A short introduction to the observables derived from magnetic resonance experiments is given. The relation of these observables to the electronic structure is sketched using the nitroxide group of spin labels as a simple example.
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Affiliation(s)
- Martina Huber
- Department of Molecular Physics, Leiden University, P.O. Box 9504, 2300RA Leiden, The Netherlands.
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Raguz M, Widomska J, Dillon J, Gaillard ER, Subczynski WK. Physical properties of the lipid bilayer membrane made of cortical and nuclear bovine lens lipids: EPR spin-labeling studies. Biochim Biophys Acta 2009; 1788:2380-8. [PMID: 19761756 PMCID: PMC2767447 DOI: 10.1016/j.bbamem.2009.09.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2009] [Revised: 08/24/2009] [Accepted: 09/06/2009] [Indexed: 11/15/2022]
Abstract
The physical properties of membranes derived from the total lipids extracted from the lens cortex and nucleus of a 2-year-old cow were investigated using EPR spin-labeling methods. Conventional EPR spectra and saturation-recovery curves show that spin labels detect a single homogenous environment in membranes made from cortical lipids. Properties of these membranes are very similar to those reported by us for membranes made of the total lipid extract of 6-month-old calf lenses (J. Widomska, M. Raguz, J. Dillon, E. R. Gaillard, W. K. Subczynski, Biochim. Biophys. Acta 1768 (2007) 1454-1465). However, in membranes made from nuclear lipids, two domains were detected by the EPR discrimination by oxygen transport method using the cholesterol analogue spin label and were assigned to the bulk phospholipid-cholesterol domain (PCD) and the immiscible cholesterol crystalline domain (CCD), respectively. Profiles of the order parameter, hydrophobicity, and the oxygen transport parameter are practically identical in the bulk PCD when measured for either the cortical or nuclear lipid membranes. In both membranes, lipids in the bulk PCD are strongly immobilized at all depths. Hydrophobicity and oxygen transport parameter profiles have a rectangular shape with an abrupt change between the C9 and C10 positions, which is approximately where the steroid ring structure of cholesterol reaches into the membrane. The permeability coefficient for oxygen, estimated at 35 degrees C, across the bulk PCD in both membranes is slightly lower than across the water layer of the same thickness. However, the evaluated upper limit of the permeability coefficient for oxygen across the CCD (34.4 cm/s) is significantly lower than across the water layer of the same thickness (85.9 cm/s), indicating that the CCD can significantly reduce oxygen transport in the lens nucleus.
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Affiliation(s)
- Marija Raguz
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
| | - Justyna Widomska
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
- Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland
| | - James Dillon
- Department of Ophthalmology, Columbia University, New York, New York 10032, USA
| | - Elizabeth R. Gaillard
- Department of Ophthalmology, Columbia University, New York, New York 10032, USA
- Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois, 60115, USA
| | - Witold K. Subczynski
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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Aluri S, Janib SM, Mackay JA. Environmentally responsive peptides as anticancer drug carriers. Adv Drug Deliv Rev 2009; 61:940-52. [PMID: 19628014 PMCID: PMC2757494 DOI: 10.1016/j.addr.2009.07.002] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Revised: 07/07/2009] [Accepted: 07/08/2009] [Indexed: 01/08/2023]
Abstract
The tumor microenvironment provides multiple cues that may be exploited to improve the efficacy of established chemotherapeutics; furthermore, polypeptides are uniquely situated to capitalize on these signals. Peptides provide: 1) a rich repertoire of biologically specific interactions to draw upon; 2) environmentally responsive phase behaviors, which may be tuned to respond to signatures of disease; 3) opportunities to direct self-assembly; 4) control over routes of biodegradation; 5) the option to seamlessly combine functionalities into a single polymer via a one-step biosynthesis. As development of cancer-targeted nanocarriers expands, peptides provide a unique source of functional units that may target disease. This review explores potential microenvironmental physiology indicative of tumors and peptides that have demonstrated an ability to target and deliver to these signals.
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Affiliation(s)
- Suhaas Aluri
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, CA, 90033-9121, USA
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Bobko AA, Dhimitruka I, Eubank TD, Marsh CB, Zweier JL, Khramtsov VV. Trityl-based EPR probe with enhanced sensitivity to oxygen. Free Radic Biol Med 2009; 47:654-8. [PMID: 19523513 PMCID: PMC2739013 DOI: 10.1016/j.freeradbiomed.2009.06.007] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2009] [Revised: 06/03/2009] [Accepted: 06/05/2009] [Indexed: 11/27/2022]
Abstract
An asymmetric derivative of the triarylmethyl radical, TAM-H, containing one aldehyde and two carboxyl groups, was synthesized. The electron paramagnetic resonance (EPR) spectrum of TAM-H is characterized by a doublet of narrow lines with a linewidth of 105 mG under anoxic conditions and hyperfine interaction constant of 245 mG. The partial overlap of the components of the doublet results in enhanced sensitivity of the spectral amplitudes ratio to oxygen compared with oxygen-induced linewidth broadening of a single line. Application of the TAM-H probe allows for EPR measurements in an extended range of oxygen pressures from atmospheric to 1 mm Hg, whereas the EPR spectrum linewidth of the popular TAM-based oxygen sensor Oxo63 is practically insensitive to oxygen partial pressures below 20 mm Hg. Enhanced sensitivity of the TAM-H probe relative to Oxo63 was demonstrated in the detection of oxygen consumption by Met-1 cancer cells. The TAM-H probe allowed prolonged measurements of oxygen depletion during the hypoxia stage and down to true anoxia (<or=1.5 mm Hg).
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Affiliation(s)
- Andrey A Bobko
- Dorothy M. Davis Heart & Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
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