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Thelen JL, Leite W, Urban VS, O'Neill HM, Grishaev AV, Curtis JE, Krueger S, Castellanos MM. Morphological Characterization of Self-Amplifying mRNA Lipid Nanoparticles. ACS Nano 2024; 18:1464-1476. [PMID: 38175970 DOI: 10.1021/acsnano.3c08014] [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] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2024]
Abstract
The mRNA technology has emerged as a rapid modality to develop vaccines during pandemic situations with the potential to protect against endemic diseases. The success of mRNA in producing an antigen is dependent on the ability to deliver mRNA to the cells using a vehicle, which typically consists of a lipid nanoparticle (LNP). Self-amplifying mRNA (SAM) is a synthetic mRNA platform that, besides encoding for the antigen of interest, includes the replication machinery for mRNA amplification in the cells. Thus, SAM can generate many antigen encoding mRNA copies and prolong expression of the antigen with lower doses than those required for conventional mRNA. This work describes the morphology of LNPs containing encapsulated SAM (SAM LNPs), with SAM being three to four times larger than conventional mRNA. We show evidence that SAM changes its conformational structure when encapsulated in LNPs, becoming more compact than the free SAM form. A characteristic "bleb" structure is observed in SAM LNPs, which consists of a lipid-rich core and an aqueous RNA-rich core, both surrounded by a DSPC-rich lipid shell. We used SANS and SAXS data to confirm that the prevalent morphology of the LNP consists of two-core compartments where components are heterogeneously distributed between the two cores and the shell. A capped cylinder core-shell model with two interior compartments was built to capture the overall morphology of the LNP. These findings provide evidence that bleb two-compartment structures can be a representative morphology in SAM LNPs and highlight the need for additional studies that elucidate the role of spherical and bleb morphologies, their mechanisms of formation, and the parameters that lead to a particular morphology for a rational design of LNPs for mRNA delivery.
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Affiliation(s)
- Jacob L Thelen
- GSK, Rockville Center for Vaccines Research, 14200 Shady Grove Road, Rockville, Maryland 20850, United States
| | - Wellington Leite
- Neutron Scattering Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
| | - Volker S Urban
- Neutron Scattering Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
| | - Hugh M O'Neill
- Neutron Scattering Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
| | - Alexander V Grishaev
- Institute for Bioscience and Biotechnology Research, University of Maryland, 9600 Gudelsky Drive, Rockville, Maryland 20850, United States
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
| | - Joseph E Curtis
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
| | - Susan Krueger
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - Maria Monica Castellanos
- GSK, Rockville Center for Vaccines Research, 14200 Shady Grove Road, Rockville, Maryland 20850, United States
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Oehler MA, Hayes DG, D’Souza DH, Senanayake M, Gurumoorthy V, Pingali SV, O’Neill HM, Bras W, Urban VS. Assessment of antimicrobial activity of melittin encapsulated in bicontinuous microemulsions prepared using renewable oils. J SURFACTANTS DETERG 2023; 26:387-399. [PMID: 37470058 PMCID: PMC10353728 DOI: 10.1002/jsde.12654] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Accepted: 12/13/2022] [Indexed: 12/29/2022]
Abstract
The objective of this study is to demonstrate that melittin, a well-studied antimicrobial peptide (AMP), can be solubilized in an active form in bicontinuous microemulsions (BMEs) that employ biocompatible oils. The systems investigated consisted of Winsor-III and -IV BME phases composed of Water/Aerosol-OT (AOT)/Polysorbate 85/isopropyl myristate and a Winsor-IV BME employing Polysorbate 80 and limonene. We found that melittin resided in an α-helix-rich configuration and was in an apolar environment for the AOT/Polysorbate 85 Winsor-III system, suggesting that melittin interacted with the surfactant monolayer and was in an active conformation. An apolar environment was also detected for melittin in the two Winsor-IV systems, but to a lesser extent than the Winsor-III system. Small-angle X-ray scattering analysis indicated that melittin at a concentration of 1.0 g/Laq in the aqueous subphase of the Winsor-IV systems led to the greatest impact on the BME structure (e.g., decrease of quasi-periodic repeat distance and correlation length and induction of interfacial fluidity). The antimicrobial activity of the Polysorbate 80 Winsor-IV system was evaluated against several bacteria prominent in chronic wounds and surgical site infections (SSIs). Melittin-free BMEs inhibited the growth of all tested bacteria due to its oil, limonene, while the inclusion of 1.0 g/Laq of melittin in the BMEs enhanced the activity against several bacteria. A further increase of melittin concentration in the BMEs had no further enhancement. These results demonstrate the potential utility of BMEs as a delivery platform for AMPs and other hydrophilic and lipophilic drugs to inhibit antibiotic-resistant microorganisms in chronic wounds and SSIs.
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Affiliation(s)
- Madison A. Oehler
- Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, Tennessee, USA
| | - Douglas G. Hayes
- Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, Tennessee, USA
| | - Doris H. D’Souza
- Department of Food Science, University of Tennessee, Knoxville, Tennessee, USA
| | - Manjula Senanayake
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | | | - Sai Venkatesh Pingali
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Hugh M. O’Neill
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Wim Bras
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Volker S. Urban
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
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Astner AF, Hayes DG, O'Neill H, Evans BR, Pingali SV, Urban VS, Schaeffer SM, Young TM. Assessment of cryogenic pretreatment for simulating environmental weathering in the formation of surrogate micro- and nanoplastics from agricultural mulch film. Sci Total Environ 2023; 870:161867. [PMID: 36716885 DOI: 10.1016/j.scitotenv.2023.161867] [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] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 01/11/2023] [Accepted: 01/23/2023] [Indexed: 06/18/2023]
Abstract
Microplastics (MPs) and nanoplastics (NPs) from mulch films and other plastic materials employed in vegetable and small fruit production pose a major threat to agricultural ecosystems. For conducting controlled studies on MPs' and NPs' (MNPs') ecotoxicity to soil organisms and plants and fate and transport in soil, surrogate MNPs are required that mimic MNPs that form in agricultural fields. We have developed a procedure to prepare MPs from plastic films or pellets using mechanical milling and sieving, and conversion of the resultant MPs into NPs through wet grinding, both steps of which mimic the degradation and fragmentation of plastics in nature. The major goal of this study was to determine if cryogenic exposure of two biodegradable mulch films effectively mimics the embrittlement caused by environmental weathering in terms of the dimensional, thermal, chemical, and biodegradability properties of the formed MNPs. We found differences in size, surface charge, thermal and chemical properties, and biodegradability in soil between MNPs prepared from cryogenically treated vs. environmentally weathered films, related to the photochemical reactions occurring in the environment that were not mimicked by cryogenic treatment, such as depolymerization and cross-link formation. We also investigated the size reduction process for NPs and found that the size distribution was bimodal, with populations centered at 50 nm and 150-300 nm, and as the size reduction process progressed, the former subpopulation's proportion increased. The biodegradability of MPs in soil was greater than for NPs, a counter-intuitive trend since greater surface area exposure for NPs would increase biodegradability. The result isassociated with differences in surface and chemical properties and to minor components that are readily leached out during the formation of NPs. In summary, the use of weathered plastics as feedstock would likely produce MNPs that are more realistic than cryogenically-treated unweathered films for use in experimental studies.
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Affiliation(s)
- A F Astner
- The University of Tennessee, Biosystems Engineering and Soil Science, 2506 E J. Chapman Dr, Knoxville, TN 37996, United States of America
| | - D G Hayes
- The University of Tennessee, Biosystems Engineering and Soil Science, 2506 E J. Chapman Dr, Knoxville, TN 37996, United States of America.
| | - H O'Neill
- Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America
| | - B R Evans
- Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America
| | - S V Pingali
- Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America
| | - V S Urban
- Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America
| | - S M Schaeffer
- The University of Tennessee, Biosystems Engineering and Soil Science, 2506 E J. Chapman Dr, Knoxville, TN 37996, United States of America
| | - T M Young
- The University of Tennessee, School of Natural Resources, 2505 E.J. Chapman Dr, Knoxville, TN 37996, United States of America
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Gurumoorthy V, Shrestha UR, Zhang Q, Pingali SV, Boder ET, Urban VS, Smith JC, Petridis L, O'Neill H. Disordered Domain Shifts the Conformational Ensemble of the Folded Regulatory Domain of the Multidomain Oncoprotein c-Src. Biomacromolecules 2023; 24:714-723. [PMID: 36692364 DOI: 10.1021/acs.biomac.2c01158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
c-Src kinase is a multidomain non-receptor tyrosine kinase that aberrantly phosphorylates several signaling proteins in cancers. Although the structural properties of the regulatory domains (SH3-SH2) and the catalytic kinase domain have been extensively characterized, there is less knowledge about the N-terminal disordered region (SH4UD) and its interactions with the other c-Src domains. Here, we used domain-selective isotopic labeling combined with the small-angle neutron scattering contrast matching technique to study SH4UD interactions with SH3-SH2. Our results show that in the presence of SH4UD, the radius of gyration (Rg) of SH3-SH2 increases, indicating that it has a more extended conformation. Hamiltonian replica exchange molecular dynamics simulations provide a detailed molecular description of the structural changes in SH4UD-SH3-SH2 and show that the regulatory loops of SH3 undergo significant conformational changes in the presence of SH4UD, while SH2 remains largely unchanged. Overall, this study highlights how a disordered region can drive a folded region of a multidomain protein to become flexible, which may be important for allosteric interactions with binding partners. This may help in the design of therapeutic interventions that target the regulatory domains of this important family of kinases.
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Affiliation(s)
- Viswanathan Gurumoorthy
- UT/ORNL Graduate School of Genome and Science Technology, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Utsab R Shrestha
- UT/ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Qiu Zhang
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Sai Venkatesh Pingali
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Eric T Boder
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Volker S Urban
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Jeremy C Smith
- UT/ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Loukas Petridis
- UT/ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Hugh O'Neill
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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5
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Leite WC, Wu Y, Pingali SV, Lieberman RL, Urban VS. Change in Morphology of Dimyristoylphosphatidylcholine/Bile Salt Derivative Bicelle Assemblies with Dodecylmaltoside in the Disk and Ribbon Phases. J Phys Chem Lett 2022; 13:9834-9840. [PMID: 36250687 DOI: 10.1021/acs.jpclett.2c02445] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Bicelles, composed of a mixture of long and short chain lipids, form nanostructured molecular assemblies that are attractive lipid-membrane mimics for in vitro studies of integral membrane proteins. Here we study the effect of a third component, the single chain detergent n-dodecyl-β-d-maltoside (DDM) on the morphology of bicelles composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate (CHAPSO) below (10 °C) and above (38 °C) the phase transition. In the absence of DDM, bicelles convert from ellipsoidal disks at 10 °C to extended ribbon-like structures at 38 °C. The addition of DDM reshapes the ellipsoidal disc to a circular one and the flattened ribbon to a circular-cylinder worm-like micelle. Knowledge of the influence of the single chain detergent DDM on bicelle nanoscale morphology contributes toward comprehending lipid membrane self-organization and to the goal of optimizing lipid mimics for membrane biology research.
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Affiliation(s)
- Wellington C Leite
- Neutron Scattering Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
| | - Yuqi Wu
- School of Chemistry & Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, Georgia 30332-0400, United States
| | - Sai Venkatesh Pingali
- Neutron Scattering Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
| | - Raquel L Lieberman
- School of Chemistry & Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, Georgia 30332-0400, United States
| | - Volker S Urban
- Neutron Scattering Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
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6
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Astner AF, Hayes DG, O'Neill HM, Evans BR, Pingali SV, Urban VS, Young TM. Forming Micro-and Nano-Plastics from Agricultural Plastic Films for Employment in Fundamental Research Studies. J Vis Exp 2022. [DOI: 10.3791/64112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
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Copp SM, Hamblin RL, Swingle K, Rai D, Urban VS, Ivanov SA, Montaño GA. Complex pH-Dependent Interactions between Weak Polyelectrolyte Block Copolymer Micelles and Molecular Fluorophores. Langmuir 2022; 38:2038-2045. [PMID: 35119286 DOI: 10.1021/acs.langmuir.1c02889] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Amphiphilic block copolymers with weak polyelectrolyte blocks can assemble stimulus-responsive nanostructures and interfaces. Applications of these materials in drug delivery, biomimetics, and sensing largely rely on the well-understood swelling of polyelectrolyte chains upon deprotonation, often induced by changes in pH or ionic strength. This deprotonation can also tune interfacial interactions between the polyelectrolyte blocks and surrounding solution, an effect which is less studied than morphological swelling of polyelectrolytes but can be just as critical for intended function. Here, we investigate whether the pH-driven morphological response of polyelectrolyte-bearing nanostructures also affects the interactions of these nanostructures with molecules in solution, using micelles of a short-chain polybutadiene-block-poly(acrylic acid) (pBd-pAA) as a model system. We introduce a Förster resonance energy transfer (FRET) approach to probe interactions between micelles and fluorescent molecular solutes as a function of solution pH. As expected, the pAA corona of these pBd-pAA micelles increases in thickness monotonically as a function of pH. However, FRET efficiency, which provides a metric of the spatial proximity of fluorescently labeled micelles and freely diffusing fluorophores, exhibits complex nonmonotonic behavior as a function of pH, indicating that the average separation of micelles and acceptor fluorophores is not strictly correlated with micelle swelling. Dialysis experiments quantify the affinity of fluorophores for micelles as a function of pH, confirming that changes in FRET are driven almost entirely by the pH-dependent affinity of the pAA block for the investigated molecular fluorophores, not simply by a shape change of the pAA corona. This study provides key insights into the interfacial interactions between weak-polyelectrolyte-bearing nanostructures and molecular solutes, of importance for the development of their stimulus-responsive applications.
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Affiliation(s)
- Stacy M Copp
- Department of Materials Science and Engineering, University of California, Irvine, Irvine, California 92697-2585, United States
- Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697-4575, United States
- Department of Chemical and Biomolecular Engineering, University of California, Irvine, Irvine, California 92697-2580, United States
| | - Ryan L Hamblin
- Center for Integrated Nanotechnologies, Los Alamos National Laboratories, Los Alamos, New Mexico 87545, United States
| | - Kirstie Swingle
- Center for Integrated Nanotechnologies, Los Alamos National Laboratories, Los Alamos, New Mexico 87545, United States
| | - Durgesh Rai
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Volker S Urban
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Sergei A Ivanov
- Center for Integrated Nanotechnologies, Los Alamos National Laboratories, Los Alamos, New Mexico 87545, United States
| | - Gabriel A Montaño
- Department of Applied Physics and Materials Science, Northern Arizona University, Flagstaff, Arizona 86011, United States
- Center for Materials Interfaces in Research and Applications, Northern Arizona University, Flagstaff, Arizona 86011, United States
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Urban VS, Leite W, Wu Y, Pingali SV, Lieberman RL. Controlling the morphology of lipid bicelles. Acta Crystallogr A Found Adv 2021. [DOI: 10.1107/s0108767321098354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Yuan Y, Li H, Leite W, Zhang Q, Bonnesen PV, Labbé JL, Weiss KL, Pingali SV, Hong K, Urban VS, Salmon S, O'Neill H. Biosynthesis and characterization of deuterated chitosan in filamentous fungus and yeast. Carbohydr Polym 2021; 257:117637. [PMID: 33541662 DOI: 10.1016/j.carbpol.2021.117637] [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] [Received: 09/12/2020] [Revised: 11/29/2020] [Accepted: 01/09/2021] [Indexed: 10/22/2022]
Abstract
Deuterated chitosan was produced from the filamentous fungus Rhizopus oryzae, cultivated with deuterated glucose in H2O medium, without the need for conventional chemical deacetylation. After extraction and purification, the chemical composition and structure were determined by Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and small-angle neutron scattering (SANS). 13C NMR experiments provided additional information about the position of the deuterons in the glucoseamine backbone. The NMR spectra indicated that the deuterium incorporation at the non-exchangeable hydrogen positions of the aminoglucopyranosyl ring in the C3 - C5 positions was at least 60-80 %. However, the C2 position was deuterated at a much lower level (6%). Also, SANS showed that the structure of deuterated chitosan was very similar compared to the non-deuterated counterpart. The most abundant radii of the protiated and deuterated chitosan fibers were 54 Å and 60 Å, respectively, but there is a broader distribution of fiber radii in the protiated chitosan sample. The highly deuterated, soluble fungal chitosan described here can be used as a model material for studying chitosan-enzyme complexes for future neutron scattering studies. Because the physical behavior of non-deuterated fungal chitosan mimicked that of shrimp shell chitosan, the methods presented here represent a new approach to producing a high quality deuterated non-animal-derived aminopolysaccharide for studying the structure-function association of biocomposite materials in drug delivery, tissue engineering and other bioactive chitosan-based composites.
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Affiliation(s)
- Yue Yuan
- Department of Textile Engineering, Chemistry and Science, Wilson College of Textiles, North Carolina State University, Raleigh, NC, 27606, USA
| | - Hui Li
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Wellington Leite
- Center for Structural Molecular Biology, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Qiu Zhang
- Center for Structural Molecular Biology, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Peter V Bonnesen
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Jessy L Labbé
- Fungal Systems Genetics and Biology Lab, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Kevin L Weiss
- Center for Structural Molecular Biology, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Sai Venkatesh Pingali
- Center for Structural Molecular Biology, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Kunlun Hong
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Volker S Urban
- Center for Structural Molecular Biology, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Sonja Salmon
- Department of Textile Engineering, Chemistry and Science, Wilson College of Textiles, North Carolina State University, Raleigh, NC, 27606, USA.
| | - Hugh O'Neill
- Center for Structural Molecular Biology, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
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Astner AF, Hayes DG, Pingali SV, O’Neill HM, Littrell KC, Evans BR, Urban VS. Effects of soil particles and convective transport on dispersion and aggregation of nanoplastics via small-angle neutron scattering (SANS) and ultra SANS (USANS). PLoS One 2020; 15:e0235893. [PMID: 32692771 PMCID: PMC7373282 DOI: 10.1371/journal.pone.0235893] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 06/24/2020] [Indexed: 11/18/2022] Open
Abstract
Terrestrial nanoplastics (NPs) pose a serious threat to agricultural food production systems due to the potential harm of soil-born micro- and macroorganisms that promote soil fertility and ability of NPs to adsorb onto and penetrate into vegetables and other crops. Very little is known about the dispersion, fate and transport of NPs in soils. This is because of the challenges of analyzing terrestrial NPs by conventional microscopic techniques due to the low concentrations of NPs and absence of optical transparency in these systems. Herein, we investigate the potential utility of small-angle neutron scattering (SANS) and Ultra SANS (USANS) to probe the agglomeration behavior of NPs prepared from polybutyrate adipate terephthalate, a prominent biodegradable plastic used in agricultural mulching, in the presence of vermiculite, an artificial soil. SANS with the contrast matching technique was used to study the aggregation of NPs co-dispersed with vermiculite in aqueous media. We determined the contrast match point for vermiculite was 66% D2O / 33% H2O. At this condition, the signal for vermiculite was ~50–100%-fold lower that obtained using neat H2O or D2O as solvent. According to SANS and USANS, smaller-sized NPs (50 nm) remained dispersed in water and did not undergo size reduction or self-agglomeration, nor formed agglomerates with vermiculite. Larger-sized NPs (300–1000 nm) formed self-agglomerates and agglomerates with vermiculite, demonstrating their significant adhesion with soil. However, employment of convective transport (simulated by ex situ stirring of the slurries prior to SANS and USANS analyses) reduced the self-agglomeration, demonstrating weak NP-NP interactions. Convective transport also led to size reduction of the larger-sized NPs. Therefore, this study demonstrates the potential utility of SANS and USANS with contrast matching technique for investigating behavior of terrestrial NPs in complex soil systems.
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Affiliation(s)
- Anton F. Astner
- Biosystems Engineering and Soil Science, The University of Tennessee, Knoxville, Tennessee, United States of America
| | - Douglas G. Hayes
- Biosystems Engineering and Soil Science, The University of Tennessee, Knoxville, Tennessee, United States of America
- * E-mail: (DGH); (SVP)
| | - Sai Venkatesh Pingali
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- * E-mail: (DGH); (SVP)
| | - Hugh M. O’Neill
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - Kenneth C. Littrell
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - Barbara R. Evans
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - Volker S. Urban
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
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11
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Kozlovskaya V, Liu F, Yang Y, Ingle K, Qian S, Halade GV, Urban VS, Kharlampieva E. Temperature-Responsive Polymersomes of Poly(3-methyl- N-vinylcaprolactam)- block-poly( N-vinylpyrrolidone) To Decrease Doxorubicin-Induced Cardiotoxicity. Biomacromolecules 2019; 20:3989-4000. [PMID: 31503464 DOI: 10.1021/acs.biomac.9b01026] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Despite being one of the most potent chemotherapeutics, doxorubicin (DOX) facilitates cardiac toxicity by irreversibly damaging the cardiac muscle as well as severely dysregulating the immune system and impairing the resolution of cardiac inflammation. Herein, we report synthesis and aqueous self-assembly of nanosized polymersomes from temperature-responsive poly(3-methyl-N-vinylcaprolactam)-block-poly(N-vinylpyrrolidone) (PMVC-PVPON) diblock copolymers and demonstrate their potential to minimize DOX cardiotoxicity compared to liposomal DOX. RAFT polymerization of vinylpyrrolidone and 3-methyl-N-vinylcaprolactam, which are structurally similar monomers but have drastically different hydrophobicity, allows decreasing the cloud point of PMVCm-PVPONn copolymers below 20 °C. The lower critical solution temperature (LCST) of the PMVC58-PVPONn copolymer varied from 19.2 to 18.6 and to 15.2 °C by decreasing the length of the hydrophilic PVPONn block from n = 98 to n = 65 and to n = 20, respectively. The copolymers assembled into stable vesicles at room temperature when PVPON polymerization degrees were 65 and 98. Anticancer drug DOX was entrapped with high efficiency into the aqueous PMVC58-PVPON65 polymersomal core surrounded by the hydrophobic temperature-sensitive PMVC shell and the hydrophilic PVPON corona. Unlike many liposomal, micellar, or synthetic drug delivery systems, these polymersomes exhibit an exceptionally high loading capacity of DOX (49%) and encapsulation efficiency (95%) due to spontaneous loading of the drug at room temperature from aqueous DOX solution. We also show that C57BL/6J mice injected with the lethal dose of DOX at 15 mg kg-1 did not survive the 14 day treatment, resulting in 100% mortality. The DOX-loaded PMVC58-PVPON65 polymersomes did not cause any mortality in mice indicating that they can be used for successful DOX encapsulation. The gravimetric analyses of the animal organs from mice treated with liposome-encapsulated DOX (Lipo-DOX) and PMVC58-PVPON65 polymersomes (Poly-DOX) revealed that the Lipo-DOX injection caused some toxicity manifesting as decreased body weight compared to Poly-DOX and saline control. Masses of the left ventricle of the heart, lung, and spleen reduced in the Lipo-DOX-treated mice compared to the nontoxic saline control, while no significant decrease of those masses was observed for the Poly-DOX-treated mice. Our results provide evidence for superior stability of synthetic polymersomes in vivo and show promise for the development of next-generation drug carriers with minimal side effects.
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Affiliation(s)
| | | | | | | | - Shuo Qian
- Neutron Scattering Division, Neutron Sciences Directorate , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | | | - Volker S Urban
- Neutron Scattering Division, Neutron Sciences Directorate , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
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12
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Dergunov SA, Richter AG, Kim MD, Pingali SV, Urban VS, Pinkhassik E. Deciphering and Controlling Structural and Functional Parameters of the Shells in Vesicle-Templated Polymer Nanocapsules. Langmuir 2019; 35:13020-13030. [PMID: 31403799 DOI: 10.1021/acs.langmuir.9b01495] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Vesicle-templated nanocapsules are prepared by polymerization of hydrophobic acrylic monomers and cross-linkers in the hydrophobic interior of self-assembled bilayers. Understanding the mechanism of capsule formation and the influence of synthetic parameters on the structural features and functional performance of nanocapsules is critical for the rational design of functional nanodevices, an emerging trend of application of the nanocapsule platform. This study investigated the relationship between basic parameters of the formulation and synthesis of nanocapsules and structural and functional characteristics of the resulting structures. Variations in the monomer/surfactant ratio, temperature of polymerization, and the molar fraction of the free-radical initiators were investigated with a multipronged approach, including shell thickness measurements using small-angle neutron scattering, evaluation of the structural integrity of nanocapsules with scanning electron microscopy, and determination of the retention of entrapped molecules using absorbance and fluorescence spectroscopy. Surprisingly, the thickness of the shells did not correlate with the monomer/surfactant ratio, supporting the hypothesis of substantial stabilization of the surfactant bilayer with loaded monomers. Decreasing the temperature of polymerization had no effect on the spherical structure of nanocapsules but resulted in progressively lower retention of entrapped molecules, suggesting that a spherical skeleton of nanocapsule forms rapidly, followed by filling the gaps to create the structure without pinholes. Lower content of initiators resulted in slower reactions, outlining the baseline conditions for practical synthetic protocols. Taken together, these findings provide insights into the formation of nanocapsules and offer methods for controlling the properties of nanocapsules in viable synthetic methods.
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Affiliation(s)
- Sergey A Dergunov
- Department of Chemistry , University of Connecticut , 55 North Eagleville Rd. , Storrs , Connecticut 06269-3060 , United States
| | - Andrew George Richter
- Department of Physics and Astronomy , Valparaiso University , Valparaiso , Indiana 46383 , United States
| | - Mariya D Kim
- Department of Chemistry , University of Connecticut , 55 North Eagleville Rd. , Storrs , Connecticut 06269-3060 , United States
| | - Sai Venkatesh Pingali
- Center for Structural Molecular Biology , Oak Ridge National Laboratory , P.O. Box 2008 MS-6430, Oak Ridge , Tennessee 37831-6430 , United States
| | - Volker S Urban
- Center for Structural Molecular Biology , Oak Ridge National Laboratory , P.O. Box 2008 MS-6430, Oak Ridge , Tennessee 37831-6430 , United States
| | - Eugene Pinkhassik
- Department of Chemistry , University of Connecticut , 55 North Eagleville Rd. , Storrs , Connecticut 06269-3060 , United States
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13
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Astner AF, Hayes DG, O'Neill H, Evans BR, Pingali SV, Urban VS, Young TM. Mechanical formation of micro- and nano-plastic materials for environmental studies in agricultural ecosystems. Sci Total Environ 2019; 685:1097-1106. [PMID: 31390700 DOI: 10.1016/j.scitotenv.2019.06.241] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 06/10/2019] [Accepted: 06/15/2019] [Indexed: 06/10/2023]
Abstract
Release of microplastics (MPs) and nanoplastics (NPs) into agricultural fields is of great concern due to their reported ecotoxicity to organisms that provide beneficial service to the soil such as earthworms, and the potential ability of MPs and NPs to enter the food chain. Most fundamental studies of the fate and transport of plastic particulates in terrestrial environments employ idealized MP materials as models, such as monodisperse polystyrene spheres. In contrast, plastics that reside in agricultural soils consist of polydisperse fragments resulting from degraded films employed in agriculture. There exists a need for more representative materials in fundamental studies of the fate, transport, and ecotoxicity of MPs and NPs in soil ecosystems. The objective of this study was therefore to develop a procedure to produce MPs and NPs from agricultural plastics (a mulch film prepared biodegradable polymer polybutyrate adipate-co-terephthalate (PBAT) and low-density PE [LDPE]), and to characterize the resultant materials. Soaking of PBAT films under cryogenic conditions promoted embrittlement, similar to what occurs through environmental weathering. LDPE and cryogenically-treated PBAT underwent mechanical milling followed by sieve fractionation into MP fractions of 840 μm, 250 μm, 106 μm, and 45 μm. The 106 μm fraction was subjected to wet grinding to produce NPs of average particle size 366.0 nm and 389.4 nm for PBAT and LDPE, respectively. A two-parameter Weibull model described the MPs' particle size distributions, while NPs possessed bimodal distributions. Size reduction did not produce any changes in the chemical properties of the plastics, except for slight depolymerization and an increase of crystallinity resulting from cryogenic treatment. This study suggests that MPs form from cutting and high-impact mechanical degradation as would occur during the tillage into soil, and that NPs form from the MP fragments in regions of relative weakness that possess lower molecular weight polymers and crystallinity.
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Affiliation(s)
- A F Astner
- The University of Tennessee, Biosystems Engineering and Soil Science, 2506 E J. Chapman Dr, Knoxville, TN 37996, United States of America
| | - D G Hayes
- The University of Tennessee, Biosystems Engineering and Soil Science, 2506 E J. Chapman Dr, Knoxville, TN 37996, United States of America.
| | - H O'Neill
- Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America
| | - B R Evans
- Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America
| | - S V Pingali
- Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America
| | - V S Urban
- Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America
| | - T M Young
- The University of Tennessee, Center for Renewable Carbon, 2506 Jacob Dr, Knoxville, TN 37996, United States of America
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14
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Naing SH, Oliver RC, Weiss KL, Urban VS, Lieberman RL. Solution Structure of an Intramembrane Aspartyl Protease via Small Angle Neutron Scattering. Biophys J 2019; 114:602-608. [PMID: 29414706 DOI: 10.1016/j.bpj.2017.12.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 12/04/2017] [Accepted: 12/18/2017] [Indexed: 12/14/2022] Open
Abstract
Intramembrane aspartyl proteases (IAPs) comprise one of four families of integral membrane proteases that hydrolyze substrates within the hydrophobic lipid bilayer. IAPs include signal peptide peptidase, which processes remnant signal peptides from nascent polypeptides in the endoplasmic reticulum, and presenilin, the catalytic component of the γ-secretase complex that processes Notch and amyloid precursor protein. Despite their broad biomedical reach, basic structure-function relationships of IAPs remain active areas of research. Characterization of membrane-bound proteins is notoriously challenging due to their inherently hydrophobic character. For IAPs, oligomerization state in solution is one outstanding question, with previous proposals for monomer, dimer, tetramer, and octamer. Here we used small angle neutron scattering (SANS) to characterize n-dodecyl-β-D-maltopyranoside (DDM) detergent solutions containing and absent a microbial IAP ortholog. A unique feature of SANS is the ability to modulate the solvent composition to mask all but the enzyme of interest. The signal from the IAP was enhanced by deuteration and, uniquely, scattering from DDM and buffers were matched by the use of both tail-deuterated DDM and D2O. The radius of gyration calculated for IAP and the corresponding ab initio consensus model are consistent with a monomer. The model is slightly smaller than the crystallographic IAP monomer, suggesting a more compact protein in solution compared with the crystal lattice. Our study provides direct insight into the oligomeric state of purified IAP in surfactant solution, and demonstrates the utility of fully contrast-matching the detergent in SANS to characterize other intramembrane proteases and their membrane-bound substrates.
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Affiliation(s)
- Swe-Htet Naing
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia
| | - Ryan C Oliver
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Kevin L Weiss
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Volker S Urban
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee.
| | - Raquel L Lieberman
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia.
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15
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Kang TH, Compton BG, Heller WT, Qian S, Smith GS, Urban VS, Duty CE, Do C. Potentials with small‐angle neutron scattering technique for understanding structure–property relation of 3D‐printed materials. POLYM ENG SCI 2018. [DOI: 10.1002/pen.24960] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Tae Hui Kang
- Neutron Scattering Division, Oak Ridge National Laboratory Oak Ridge Tennessee 37831
| | - Brett G. Compton
- Department of Mechanical, Aerospace and Biomedical Engineering University of Tennessee Knoxville Tennessee 37996
| | - William T. Heller
- Neutron Scattering Division, Oak Ridge National Laboratory Oak Ridge Tennessee 37831
| | - Shuo Qian
- Neutron Scattering Division, Oak Ridge National Laboratory Oak Ridge Tennessee 37831
| | - Gregory S. Smith
- Neutron Scattering Division, Oak Ridge National Laboratory Oak Ridge Tennessee 37831
| | - Volker S. Urban
- Neutron Scattering Division, Oak Ridge National Laboratory Oak Ridge Tennessee 37831
| | - Chad E. Duty
- Department of Mechanical, Aerospace and Biomedical Engineering University of Tennessee Knoxville Tennessee 37996
- Manufacturing Demonstration Facility, Oak Ridge National Laboratory Oak Ridge Tennessee 37831
| | - Changwoo Do
- Neutron Scattering Division, Oak Ridge National Laboratory Oak Ridge Tennessee 37831
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16
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Oliver RC, Naing SH, Weiss KL, Pingali SV, Lieberman RL, Urban VS. Contrast-Matching Detergent in Small-Angle Neutron Scattering Experiments for Membrane Protein Structural Analysis and Ab Initio Modeling. J Vis Exp 2018:57901. [PMID: 30394373 PMCID: PMC6235576 DOI: 10.3791/57901] [Citation(s) in RCA: 1] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The biological small-angle neutron scattering instrument at the High-Flux Isotope Reactor of Oak Ridge National Laboratory is dedicated to the investigation of biological materials, biofuel processing, and bio-inspired materials covering nanometer to micrometer length scales. The methods presented here for investigating physical properties (i.e., size and shape) of membrane proteins (here, MmIAP, an intramembrane aspartyl protease from Methanoculleus marisnigri) in solutions of micelle-forming detergents are well-suited for this small-angle neutron scattering instrument, among others. Other biophysical characterization techniques are hindered by their inability to address the detergent contributions in a protein-detergent complex structure. Additionally, access to the Bio-Deuteration Lab provides unique capabilities for preparing large-scale cultivations and expressing deuterium-labeled proteins for enhanced scattering signal from the protein. While this technique does not provide structural details at high-resolution, the structural knowledge gap for membrane proteins contains many addressable areas of research without requiring near-atomic resolution. For example, these areas include determination of oligomeric states, complex formation, conformational changes during perturbation, and folding/unfolding events. These investigations can be readily accomplished through applications of this method.
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Affiliation(s)
- Ryan C Oliver
- Neutron Scattering Division, Oak Ridge National Laboratory
| | - Swe-Htet Naing
- School of Chemistry and Biochemistry, Georgia Institute of Technology
| | - Kevin L Weiss
- Neutron Scattering Division, Oak Ridge National Laboratory
| | | | | | - Volker S Urban
- Neutron Scattering Division, Oak Ridge National Laboratory;
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17
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Hayes DG, Pingali SV, O'Neill HM, Urban VS, Ye R. Observation of a structural gradient in Winsor-III microemulsion systems. Soft Matter 2018; 14:5270-5276. [PMID: 29892769 DOI: 10.1039/c8sm00322j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We demonstrate here for the first time via small-angle neutron scattering (SANS) that the middle, bicontinuous microemulsion (BμE) phase of Winsor-III systems undergoes a gradual change of structure and composition in the vertical direction, contrary to the commonly held belief of uniform structure and composition. A vertical stage was deployed to enable precise alignment of a custom-designed rectangular cell containing the WIII system with respect to the neutron beam, allowing for several different vertical positions to be analyzed. For the water/AOT/CK-2,13 (two-tailed alkyl ethoxylate containing a 1,3-dioxolane linkage)/heptane Winsor-III system, the quasi-periodic repeat distance (d) and correlation length (ξ), obtained from the Teubner-Strey model applied to the SANS data, decreased and the surface area per volume of the surfactant monolayer (via Porod analysis) increased in the downward direction, trends that reflect an increase of surfactant concentration, consistent with the ultralow interfacial tension that often occurs for the lower liquid-liquid interface of many WIII systems. The water/sodium dodecyl sulfate (SDS)/1-pentanol/dodecane system shared the same trend with regard to d as observed for AOT/CK-2,13. In contrast, for SDS/pentanol, ξ increased and the amphiphilicity factor (fa) decreased in the downward direction, trends consistent with a decrease of cosurfactant (pentanol) concentration in the downward direction. Non-uniformity in the vertical direction has implications in the transport of solutes between WIII phases during the extractive purification of proteins or the removal of heavy metals and pollutants from wastewater, or the deposition of BμEs onto hydrophilic vs. hydrophobic surfaces as thin coatings.
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Affiliation(s)
- Douglas G Hayes
- Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, TN 37996-4531, USA.
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18
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Affiliation(s)
- Hadi M. Fares
- Department of Chemistry and Biochemistry, The Florida State University, Tallahassee, Florida 32306-4390, United States
| | - Yara E. Ghoussoub
- Department of Chemistry and Biochemistry, The Florida State University, Tallahassee, Florida 32306-4390, United States
| | - Jose D. Delgado
- Department of Chemistry and Biochemistry, The Florida State University, Tallahassee, Florida 32306-4390, United States
| | - Jingcheng Fu
- Department of Chemistry and Biochemistry, The Florida State University, Tallahassee, Florida 32306-4390, United States
| | - Volker S. Urban
- Center for Structural Molecular Biology, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Joseph B. Schlenoff
- Department of Chemistry and Biochemistry, The Florida State University, Tallahassee, Florida 32306-4390, United States
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19
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Heller WT, Cuneo M, Debeer-Schmitt L, Do C, He L, Heroux L, Littrell K, Pingali SV, Qian S, Stanley C, Urban VS, Wu B, Bras W. The suite of small-angle neutron scattering instruments at Oak Ridge National Laboratory. J Appl Crystallogr 2018. [DOI: 10.1107/s1600576718001231] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Oak Ridge National Laboratory is home to the High Flux Isotope Reactor (HFIR), a high-flux research reactor, and the Spallation Neutron Source (SNS), the world's most intense source of pulsed neutron beams. The unique co-localization of these two sources provided an opportunity to develop a suite of complementary small-angle neutron scattering instruments for studies of large-scale structures: the GP-SANS and Bio-SANS instruments at the HFIR and the EQ-SANS and TOF-USANS instruments at the SNS. This article provides an overview of the capabilities of the suite of instruments, with specific emphasis on how they complement each other. A description of the plans for future developments including greater integration of the suite into a single point of entry for neutron scattering studies of large-scale structures is also provided.
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20
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Naing SH, Kalyoncu S, Smalley DM, Kim H, Tao X, George JB, Jonke AP, Oliver RC, Urban VS, Torres MP, Lieberman RL. Both positional and chemical variables control in vitro proteolytic cleavage of a presenilin ortholog. J Biol Chem 2018; 293:4653-4663. [PMID: 29382721 DOI: 10.1074/jbc.ra117.001436] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 01/23/2018] [Indexed: 11/06/2022] Open
Abstract
Mechanistic details of intramembrane aspartyl protease (IAP) chemistry, which is central to many biological and pathogenic processes, remain largely obscure. Here, we investigated the in vitro kinetics of a microbial intramembrane aspartyl protease (mIAP) fortuitously acting on the renin substrate angiotensinogen and the C-terminal transmembrane segment of amyloid precursor protein (C100), which is cleaved by the presenilin subunit of γ-secretase, an Alzheimer disease (AD)-associated IAP. mIAP variants with substitutions in active-site and putative substrate-gating residues generally exhibit impaired, but not abolished, activity toward angiotensinogen and retain the predominant cleavage site (His-Thr). The aromatic ring, but not the hydroxyl substituent, within Tyr of the catalytic Tyr-Asp (YD) motif plays a catalytic role, and the hydrolysis reaction incorporates bulk water as in soluble aspartyl proteases. mIAP hydrolyzes the transmembrane region of C100 at two major presenilin cleavage sites, one corresponding to the AD-associated Aβ42 peptide (Ala-Thr) and the other to the non-pathogenic Aβ48 (Thr-Leu). For the former site, we observed more favorable kinetics in lipid bilayer-mimicking bicelles than in detergent solution, indicating that substrate-lipid and substrate-enzyme interactions both contribute to catalytic rates. High-resolution MS analyses across four substrates support a preference for threonine at the scissile bond. However, results from threonine-scanning mutagenesis of angiotensinogen demonstrate a competing positional preference for cleavage. Our results indicate that IAP cleavage is controlled by both positional and chemical factors, opening up new avenues for selective IAP inhibition for therapeutic interventions.
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Affiliation(s)
- Swe-Htet Naing
- School of Chemistry and Biochemistry, Atlanta, Georgia 30332
| | - Sibel Kalyoncu
- School of Chemistry and Biochemistry, Atlanta, Georgia 30332
| | - David M Smalley
- Petit Institute for Bioengineering and Biosciences, Atlanta, Georgia 30332
| | - Hyojung Kim
- School of Chemistry and Biochemistry, Atlanta, Georgia 30332; School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Xingjian Tao
- School of Chemistry and Biochemistry, Atlanta, Georgia 30332
| | - Josh B George
- School of Chemistry and Biochemistry, Atlanta, Georgia 30332
| | - Alex P Jonke
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Ryan C Oliver
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
| | - Volker S Urban
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
| | - Matthew P Torres
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332
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21
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Hayes DG, Ye R, Dunlap RN, Anunciado DB, Pingali SV, O'Neill HM, Urban VS. Bicontinuous microemulsions as a biomembrane mimetic system for melittin. Biochim Biophys Acta Biomembr 2017; 1860:624-632. [PMID: 29138064 DOI: 10.1016/j.bbamem.2017.11.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 10/06/2017] [Accepted: 11/10/2017] [Indexed: 01/26/2023]
Abstract
Antimicrobial peptides effectively kill antibiotic-resistant bacteria by forming pores in prokaryotes' biomembranes via penetration into the biomembranes' interior. Bicontinuous microemulsions, consisting of interdispersed oil and water nanodomains separated by flexible surfactant monolayers, are potentially valuable for hosting membrane-associated peptides and proteins due to their thermodynamic stability, optical transparency, low viscosity, and high interfacial area. Here, we show that bicontinuous microemulsions formed by negatively-charged surfactants are a robust biomembrane mimetic system for the antimicrobial peptide melittin. When encapsulated in bicontinuous microemulsions formed using three-phase (Winsor-III) systems, melittin's helicity increases greatly due to penetration into the surfactant monolayers, mimicking its behavior in biomembranes. But, the threshold melittin concentration required to achieve these trends is lower for the microemulsions. The extent of penetration was decreased when the interfacial fluidity of the microemulsions was increased. These results suggest the utility of bicontinuous microemulsions for isolation, purification, delivery, and host systems for antimicrobial peptides.
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Affiliation(s)
- Douglas G Hayes
- Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, TN 37996-4531, USA.
| | - Ran Ye
- Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, TN 37996-4531, USA
| | - Rachel N Dunlap
- Biology & Soft Matter Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6475, USA
| | - Divina B Anunciado
- Biology & Soft Matter Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6475, USA
| | - Sai Venkatesh Pingali
- Biology & Soft Matter Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6475, USA
| | - Hugh M O'Neill
- Biology & Soft Matter Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6475, USA
| | - Volker S Urban
- Biology & Soft Matter Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6475, USA.
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22
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Abstract
Micelle-forming detergents provide an amphipathic environment that mimics lipid bilayers and are important tools used to solubilize and stabilize membrane proteins in solution for in vitro structural investigations. Small-angle neutron scattering (SANS) at the neutron contrast match point of detergent molecules allows observing the signal from membrane proteins unobstructed by contributions from the detergent. However, we show that even for a perfectly average-contrast matched detergent there arises significant core-shell scattering from the contrast difference between aliphatic detergent tails and hydrophilic head groups. This residual signal interferes with interpreting structural data of membrane proteins. This complication is often made worse by the presence of excess empty (protein-free) micelles. We present an approach for the rational design of mixed micelles containing a deuterated detergent analog, which eliminates neutron contrast between core and shell and allows the micelle scattering to be fully contrast-matched to unambiguously resolve membrane protein structure using solution SANS.
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Affiliation(s)
- Ryan C Oliver
- Center for Structural Molecular Biology and Biology and Soft Matter Division, Oak Ridge National Laboratory , P.O. Box 2008, MS 6475, Oak Ridge, Tennessee 37831, United States
| | - Sai Venkatesh Pingali
- Center for Structural Molecular Biology and Biology and Soft Matter Division, Oak Ridge National Laboratory , P.O. Box 2008, MS 6475, Oak Ridge, Tennessee 37831, United States
| | - Volker S Urban
- Center for Structural Molecular Biology and Biology and Soft Matter Division, Oak Ridge National Laboratory , P.O. Box 2008, MS 6475, Oak Ridge, Tennessee 37831, United States
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23
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Hayes DG, Ye R, Dunlap RN, Cuneo MJ, Pingali SV, O'Neill HM, Urban VS. Protein extraction into the bicontinuous microemulsion phase of a Water/SDS/pentanol/dodecane winsor-III system: Effect on nanostructure and protein conformation. Colloids Surf B Biointerfaces 2017; 160:144-153. [PMID: 28922633 DOI: 10.1016/j.colsurfb.2017.09.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Revised: 08/22/2017] [Accepted: 09/04/2017] [Indexed: 02/04/2023]
Abstract
Bicontinuous microemulsions (BμEs), consisting of water and oil nanodomains separated by surfactant monolayers of near-zero curvature, are potentially valuable systems for purification and delivery of biomolecules, for hosting multiphasic biochemical reactions, and as templating media for preparing nanomaterials. We formed Winsor-III systems by mixing aqueous protein and sodium dodecyl sulfate (SDS) solutions with dodecane and 1-pentanol (cosurfactant) to efficiently extract proteins into the middle (BμE) phase. Bovine serum albumin (BSA) and cytochrome c partitioned to the BμE phase at 64% and 81% efficiency, respectively, producing highly concentrated protein solutions (32 and 44gL-1, respectively), through release of water and oil from the BμEs. Circular dichroism spectroscopic analysis demonstrated that BSA underwent minor secondary structural changes upon incorporation into BμEs, while the secondary structure of cytochrome c and pepsin underwent major changes. Small-angle x-ray scattering (SAXS) results show that proteins promoted an increase of the interfacial fluidity and surface area per volume for the BμE surfactant monolayers, and that each protein uniquely altered self-assembly in the Winsor-III systems. Cytochrome c partitioned via electrostatic attractions between SDS and the protein's positively-charged groups, residing near the surfactant head groups of BμE monolayers, where it decreased surfactant packing efficiency. BSA partitioned through formation of SDS-BSA complexes via hydrophobic and electrostatic attractive interactions. As the BSA-SDS ratio increased, complexes' partitioning favored BμEs over the oil excess phase due to the increased hydrophilicity of the complexes. This study demonstrates the potential utility of BμEs to purify proteins and prepare nanostructured fluids possessing high protein concentration.
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Affiliation(s)
- Douglas G Hayes
- Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, TN 37996-4531 USA.
| | - Ran Ye
- Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, TN 37996-4531 USA
| | - Rachel N Dunlap
- Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, TN 37996-4531 USA; Biology & Soft Matter Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6475, USA
| | - Matthew J Cuneo
- Biology & Soft Matter Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6475, USA
| | - Sai Venkatesh Pingali
- Biology & Soft Matter Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6475, USA
| | - Hugh M O'Neill
- Biology & Soft Matter Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6475, USA
| | - Volker S Urban
- Biology & Soft Matter Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6475, USA
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Richter AG, Dergunov SA, Kim MD, Shmakov SN, Pingali SV, Urban VS, Liu Y, Pinkhassik E. Unraveling the Single-Nanometer Thickness of Shells of Vesicle-Templated Polymer Nanocapsules. J Phys Chem Lett 2017; 8:3630-3636. [PMID: 28715200 DOI: 10.1021/acs.jpclett.7b01149] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Vesicle-templated nanocapsules have emerged as a viable platform for diverse applications. Shell thickness is a critical structural parameter of nanocapsules, where the shell plays a crucial role providing mechanical stability and control of permeability. Here we used small-angle neutron scattering (SANS) to determine the thickness of freestanding and surfactant-stabilized nanocapsules. Despite being at the edge of detectability, we were able to show the polymer shell thickness to be typically 1.0 ± 0.1 nm, which places vesicle-templated nanocapsules among the thinnest materials ever created. The extreme thinness of the shells has implications for several areas: mass-transport through nanopores is relatively unimpeded; pore-forming molecules are not limited to those spanning the entire bilayer; the internal volume of the capsules is maximized; and insight has been gained on how polymerization occurs in the confined geometry of a bilayer scaffold, being predominantly located at the phase-separated layer of monomers and cross-linkers between the surfactant leaflets.
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Affiliation(s)
- Andrew G Richter
- Department of Physics and Astronomy, Valparaiso University , Valparaiso, Indiana 46383, United States
| | - Sergey A Dergunov
- Department of Chemistry, University of Connecticut , 55 North Eagleville Rd, Storrs, Connecticut 06269-3060, United States
| | - Mariya D Kim
- Department of Chemistry, University of Connecticut , 55 North Eagleville Rd, Storrs, Connecticut 06269-3060, United States
| | - Sergey N Shmakov
- Department of Chemistry, University of Connecticut , 55 North Eagleville Rd, Storrs, Connecticut 06269-3060, United States
| | - Sai Venkatesh Pingali
- Center for Structural Molecular Biology, Oak Ridge National Laboratory , P.O. Box 2008 MS-6430, Oak Ridge, Tennessee 37831-6430, United States
| | - Volker S Urban
- Center for Structural Molecular Biology, Oak Ridge National Laboratory , P.O. Box 2008 MS-6430, Oak Ridge, Tennessee 37831-6430, United States
| | - Yun Liu
- Department of Chemical and Biological Engineering, University of Delaware , Newark, Delaware 19716, United States
- Center for Neutron Science, National Institute of Standards and Technology , 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
| | - Eugene Pinkhassik
- Department of Chemistry, University of Connecticut , 55 North Eagleville Rd, Storrs, Connecticut 06269-3060, United States
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25
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Sharma VK, Hayes DG, Urban VS, O'Neill HM, Tyagi M, Mamontov E. Nanoscopic dynamics of bicontinous microemulsions: effect of membrane associated protein. Soft Matter 2017. [PMID: 28631792 DOI: 10.1039/c7sm00875a] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Bicontinous microemulsions (BμE) generally consist of nanodomains formed by surfactant in a mixture of water and oil at nearly equal proportions and are potential candidates for the solubilization and purification of membrane proteins. Here we present the first time report of nanoscopic dynamics of surfactant monolayers within BμEs formed by the anionic surfactant sodium dodecyl sulfate (SDS) measured on the nanosecond to picosecond time scale using quasielastic neutron scattering (QENS). BμEs investigated herein consisted of middle phases isolated from Winsor-III microemulsion systems that were formed by mixing aqueous and oil solutions under optimal conditions. QENS data indicates that surfactants undergo two distinct motions, namely (i) lateral motion along the surface of the oil nanodomains and (ii) localized internal motion. Lateral motion can be described using a continuous diffusion model, from which the lateral diffusion coefficient is obtained. Internal motion of surfactant is described using a model which assumes that a fraction of the surfactants' hydrogens undergoes localized translational diffusion that could be considered confined within a spherical volume. The effect of cytochrome c, an archetypal membrane-associated protein known to strongly partition near the surfactant head groups in BμEs (a trend supported by small-angle X-ray scattering [SAXS] analysis), on the dynamics of BμE has also been investigated. QENS results demonstrated that cytochrome c significantly hindered both the lateral and the internal motions of surfactant. The lateral motion was more strongly affected: a reduction of the lateral diffusion coefficient by 33% was measured. This change is mainly attributable to the strong association of cytochrome c with oppositely charged SDS. In contrast, analysis of SAXS data suggested that thermal fluctuations (for a longer length and slower time scale compared to QENS) were increased upon incorporation of cytochrome c. This study demonstrates the utility of QENS for evaluating dynamics of BμEs in nanoscopic region, and that proteins directly affect the microscopic dynamics, which is of relevance for evaluating release kinetics of encapsulated drugs from BμE delivery systems and the use of BμEs as biomembrane mimetic systems for investigating membrane protein-biomembrane interactions.
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Affiliation(s)
- V K Sharma
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
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26
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Urban VS, Rai DK, Gurusaran M, Renugopalakrishnan V. Hybrid approach for analyzing SAS data from enzyme–graphene nanocomposite. Acta Crystallogr A Found Adv 2017. [DOI: 10.1107/s0108767317096441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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27
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Sharma VK, Mamontov E, Tyagi M, Qian S, Rai DK, Urban VS. Dynamical and Phase Behavior of a Phospholipid Membrane Altered by an Antimicrobial Peptide at Low Concentration. J Phys Chem Lett 2016; 7:2394-401. [PMID: 27232190 DOI: 10.1021/acs.jpclett.6b01006] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The mechanism of action of antimicrobial peptides is traditionally attributed to the formation of pores in the lipid cell membranes of pathogens, which requires a substantial peptide to lipid ratio. However, using incoherent neutron scattering, we show that even at a concentration too low for pore formation, an archetypal antimicrobial peptide, melittin, disrupts the regular phase behavior of the microscopic dynamics in a phospholipid membrane, dimyristoylphosphatidylcholine (DMPC). At the same time, another antimicrobial peptide, alamethicin, does not exert a similar effect on the DMPC microscopic dynamics. The melittin-altered lateral motion of DMPC at physiological temperature no longer resembles the fluid-phase behavior characteristic of functional membranes of the living cells. The disruptive effect demonstrated by melittin even at low concentrations reveals a new mechanism of antimicrobial action relevant in more realistic scenarios, when peptide concentration is not as high as would be required for pore formation, which may facilitate treatment with antimicrobial peptides.
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Affiliation(s)
- V K Sharma
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
- Solid State Physics Division, Bhabha Atomic Research Centre , Mumbai 400085, India
| | - E Mamontov
- Chemical and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - M Tyagi
- National Institute of Standards and Technology Center for Neutron Research , Gaithersburg, Maryland 20899, United States
- Department of Materials Science and Engineering, University of Maryland , College Park, Maryland 20742, United States
| | - S Qian
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - D K Rai
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - V S Urban
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
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28
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Sharma VK, Mamontov E, Anunciado DB, O'Neill H, Urban VS. Effect of antimicrobial peptide on the dynamics of phosphocholine membrane: role of cholesterol and physical state of bilayer. Soft Matter 2015. [PMID: 26212615 DOI: 10.1039/c5sm01562f] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Antimicrobial peptides are universal in all forms of life and are well known for their strong interaction with the cell membrane. This makes them a popular target for investigation of peptide-lipid interactions. Here we report the effect of melittin, an important antimicrobial peptide, on the dynamics of membranes based on 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid in both the solid gel and fluid phases. To probe the phase transition, elastic neutron intensity temperature scans have been carried out on DMPC-based unilamellar vesicles (ULV) with and without melittin. We have found that addition of a small amount (0.2 mol%) melittin eliminates the steep fall in the elastic intensity at 296 K associated with the solid gel to fluid phase transition, which is observed for pure DMPC vesicles. Quasielastic neutron scattering (QENS) experiments have been carried out on DMPC ULV in the solid gel and fluid phases with and without 0.2 mol% melittin. The data analysis invariably shows the presence of lateral and internal motions of the DMPC molecule. We found that melittin does have a profound effect on the dynamics of lipid molecules, especially on the lateral motion, and affects it in a different way, depending on the phase of the bilayers. In the solid gel phase, it acts as a plasticizer, enhancing the lateral motion of DMPC. However, in the fluid phase it acts as a stiffening agent, restricting the lateral motion of the lipid molecules. These observations are consistent with the mean squared displacements extracted from the elastic intensity temperature scans. Their importance lies in the fact that many membrane processes, including signaling and energy transduction pathways, are controlled to a great extent by the lateral diffusion of lipids in the membrane. To investigate the effect of melittin on vesicles supplemented with cholesterol, QENS experiments have also been carried out on DMPC ULV with cholesterol in the presence and absence of 0.2 mol% melittin. Remarkably, the effects of melittin on the membrane dynamics disappear in the presence of 20 mol% cholesterol. Our measurements indicate that the destabilizing effect of the peptide melittin on membranes can be mitigated by the presence of cholesterol. This study might provide new insights into the mechanism of action of antimicrobial peptides and their selective toxicity towards foreign microorganisms.
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Affiliation(s)
- V K Sharma
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
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29
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Adams PG, Collins AM, Sahin T, Subramanian V, Urban VS, Vairaprakash P, Tian Y, Evans DG, Shreve AP, Montaño GA. Diblock copolymer micelles and supported films with noncovalently incorporated chromophores: a modular platform for efficient energy transfer. Nano Lett 2015; 15:2422-2428. [PMID: 25719733 DOI: 10.1021/nl504814x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report generation of modular, artificial light-harvesting assemblies where an amphiphilic diblock copolymer, poly(ethylene oxide)-block-poly(butadiene), serves as the framework for noncovalent organization of BODIPY-based energy donor and bacteriochlorin-based energy acceptor chromophores. The assemblies are adaptive and form well-defined micelles in aqueous solution and high-quality monolayer and bilayer films on solid supports, with the latter showing greater than 90% energy transfer efficiency. This study lays the groundwork for further development of modular, polymer-based materials for light harvesting and other photonic applications.
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Affiliation(s)
- Peter G Adams
- †Center for Integrated Nanotechnologies, Los Alamos National Laboratories, Los Alamos, New Mexico 87545, United States
| | - Aaron M Collins
- †Center for Integrated Nanotechnologies, Los Alamos National Laboratories, Los Alamos, New Mexico 87545, United States
| | - Tuba Sahin
- ‡Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Vijaya Subramanian
- §Center for Biomedical Engineering, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Volker S Urban
- ⊥Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Pothiappan Vairaprakash
- ‡Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Yongming Tian
- †Center for Integrated Nanotechnologies, Los Alamos National Laboratories, Los Alamos, New Mexico 87545, United States
- ¶Department of Chemistry, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801, United States
| | - Deborah G Evans
- §Center for Biomedical Engineering, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Andrew P Shreve
- §Center for Biomedical Engineering, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Gabriel A Montaño
- †Center for Integrated Nanotechnologies, Los Alamos National Laboratories, Los Alamos, New Mexico 87545, United States
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30
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Hayes DG, Gomez del Rio JA, Ye R, Urban VS, Pingali SV, O'Neill HM. Effect of protein incorporation on the nanostructure of the bicontinuous microemulsion phase of Winsor-III systems: a small-angle neutron scattering study. Langmuir 2015; 31:1901-1910. [PMID: 25603188 DOI: 10.1021/la504606x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Small-angle neutron scattering (SANS) analysis using the Teubner-Strey model has been employed to evaluate the effect of protein incorporation into the middle, bicontinuous microemulsion (BμE) phase of Winsor-III (WIII) systems formed by an aerosol-OT (AOT)/alkyl ethoxylate mixed surfactant system to understand better the extraction of proteins into and out of BμEs and to study the effect of proteins on a system that serves as a biomimetic analog of cell membranes. Under conditions of high salinity, the incorporation of positively charged proteins cytochrome c, lysozyme, and α-chymotrypsin, near their solubilization limit in the BμEs promoted the release of water and oil from the BμEs, a decrease in the quasi-periodic repeat distance (d), an increase in ordering (a decrease in the amphiphilicity factor, fa) for the surfactant monolayers, and a decrease in the surface area per surfactant headgroup, suggesting that the proteins affected the self-assembly of components in the BμE phase and produced Debye shielding of AOT's sulfonate headgroup. For WIII systems possessing lower salinity, cytochrome c reduced the efficiency of surfactant in the BμE phase, noted by increases in d and fa, suggesting that the enzyme and AOT underwent ion pairing. The results of this study demonstrate the importance of ionic strength to modulate protein-surfactant interactions, which in turn will control the release of proteins encapsulated in the BμEs, relevant to WIII-based protein extraction and controlled release from BμE delivery systems, and demonstrate the utility of BμEs as a model system to understand the effect of proteins on biomembranes.
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Affiliation(s)
- Douglas G Hayes
- Department of Biosystems Engineering and Soil Science, University of Tennessee , Knoxville, Tennessee 37996-4531, United States
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31
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Wang Y, Freund DM, Magdaong NM, Urban VS, Frank HA, Hegeman AD, Tang JKH. Impact of esterified bacteriochlorophylls on the biogenesis of chlorosomes in Chloroflexus aurantiacus. Photosynth Res 2014; 122:69-86. [PMID: 24880610 DOI: 10.1007/s11120-014-0017-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 05/19/2014] [Indexed: 06/03/2023]
Abstract
A chlorosome is an antenna complex located on the cytoplasmic side of the inner membrane in green photosynthetic bacteria that contains tens of thousands of self-assembled bacteriochlorophylls (BChls). Green bacteria are known to incorporate various esterifying alcohols at the C-17 propionate position of BChls in the chlorosome. The effect of these functional substitutions on the biogenesis of the chlorosome has not yet been fully explored. In this report, we address this question by investigating various esterified bacteriochlorophyll c (BChl c) homologs in the thermophilic green non-sulfur bacterium Chloroflexus aurantiacus. Cultures were supplemented with exogenous long-chain alcohols at 52 °C (an optimal growth temperature) and 44 °C (a suboptimal growth temperature), and the morphology, optical properties and exciton transfer characteristics of chlorosomes were investigated. Our studies indicate that at 44 °C Cfl. aurantiacus synthesizes more carotenoids, incorporates more BChl c homologs with unsaturated and rigid polyisoprenoid esterifying alcohols and produces more heterogeneous BChl c homologs in chlorosomes. Substitution of phytol for stearyl alcohol of BChl c maintains similar morphology of the intact chlorosome and enhances energy transfer from the chlorosome to the membrane-bound photosynthetic apparatus. Different morphologies of the intact chlorosome versus in vitro BChl aggregates are suggested by small-angle neutron scattering. Additionally, phytol cultures and 44 °C cultures exhibit slow assembly of the chlorosome. These results suggest that the esterifying alcohol of BChl c contributes to long-range organization of BChls, and that interactions between BChls with other components are important to the assembly of the chlorosome. Possible mechanisms for how esterifying alcohols affect the biogenesis of the chlorosome are discussed.
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Affiliation(s)
- Yaya Wang
- Department of Chemistry and Biochemistry, Clark University, Worcester, MA, 01610, USA
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32
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Heller WT, Urban VS, Lynn GW, Weiss KL, O'Neill HM, Pingali SV, Qian S, Littrell KC, Melnichenko YB, Buchanan MV, Selby DL, Wignall GD, Butler PD, Myles DA. The Bio-SANS instrument at the High Flux Isotope Reactor of Oak Ridge National Laboratory. J Appl Crystallogr 2014. [DOI: 10.1107/s1600576714011285] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Small-angle neutron scattering (SANS) is a powerful tool for characterizing complex disordered materials, including biological materials. The Bio-SANS instrument of the High Flux Isotope Reactor of Oak Ridge National Laboratory (ORNL) is a high-flux low-background SANS instrument that is, uniquely among SANS instruments, dedicated to serving the needs of the structural biology and biomaterials communities as an open-access user facility. Here, the technical specifications and performance of the Bio-SANS are presented. Sample environments developed to address the needs of the user program of the instrument are also presented. Further, the isotopic labeling and sample preparation capabilities available in the Bio-Deuteration Laboratory for users of the Bio-SANS and other neutron scattering instruments at ORNL are described. Finally, a brief survey of research performed using the Bio-SANS is presented, which demonstrates the breadth of the research that the instrument's user community engages in.
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33
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Kim MD, Dergunov SA, Richter AG, Durbin J, Shmakov SN, Jia Y, Kenbeilova S, Orazbekuly Y, Kengpeiil A, Lindner E, Pingali SV, Urban VS, Weigand S, Pinkhassik E. Facile directed assembly of hollow polymer nanocapsules within spontaneously formed catanionic surfactant vesicles. Langmuir 2014; 30:7061-7069. [PMID: 24341533 DOI: 10.1021/la404026w] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Surfactant vesicles containing monomers in the interior of the bilayer were used to template hollow polymer nanocapsules. This study investigated the formation of surfactant/monomer assemblies by two loading methods, concurrent loading and diffusion loading. The assembly process and the resulting aggregates were investigated with dynamic light scattering, small angle neutron scattering, and small-angle X-ray scattering. Acrylic monomers formed vesicles with a mixture of cationic and anionic surfactants in a broad range of surfactant ratios. Regions with predominant formation of vesicles were broader for compositions containing acrylic monomers compared with blank surfactants. This observation supports the stabilization of the vesicular structure by acrylic monomers. Diffusion loading produced monomer-loaded vesicles unless vesicles were composed from surfactants at the ratios close to the boundary of a vesicular phase region on a phase diagram. Both concurrent-loaded and diffusion-loaded surfactant/monomer vesicles produced hollow polymer nanocapsules upon the polymerization of monomers in the bilayer followed by removal of surfactant scaffolds.
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Affiliation(s)
- Mariya D Kim
- Department of Chemistry, Saint Louis University , 3501 Laclede Avenue, St. Louis, Missouri 63103, United States
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Tang JKH, Saikin SK, Pingali SV, Enriquez MM, Huh J, Frank HA, Urban VS, Aspuru-Guzik A. Temperature and carbon assimilation regulate the chlorosome biogenesis in green sulfur bacteria. Biophys J 2014; 105:1346-56. [PMID: 24047985 DOI: 10.1016/j.bpj.2013.07.027] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 07/19/2013] [Accepted: 07/23/2013] [Indexed: 11/16/2022] Open
Abstract
Green photosynthetic bacteria adjust the structure and functionality of the chlorosome-the light-absorbing antenna complex-in response to environmental stress factors. The chlorosome is a natural self-assembled aggregate of bacteriochlorophyll (BChl) molecules. In this study, we report the regulation of the biogenesis of the Chlorobaculum tepidum chlorosome by carbon assimilation in conjunction with temperature changes. Our studies indicate that the carbon source and thermal stress culture of C. tepidum grows slower and incorporates fewer BChl c in the chlorosome. Compared with the chlorosome from other cultural conditions we investigated, the chlorosome from the carbon source and thermal stress culture displays (a) smaller cross-sectional radius and overall size, (b) simplified BChl c homologs with smaller side chains, (c) blue-shifted Qy absorption maxima, and (d) a sigmoid-shaped circular dichroism spectra. Using a theoretical model, we analyze how the observed spectral modifications can be associated with structural changes of BChl aggregates inside the chlorosome. Our report suggests a mechanism of metabolic regulation for chlorosome biogenesis.
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35
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Ortony JH, Choi SH, Spruell JM, Hunt JN, Lynd NA, Krogstad DV, Urban VS, Hawker CJ, Kramer EJ, Han S. Fluidity and water in nanoscale domains define coacervate hydrogels. Chem Sci 2014. [DOI: 10.1039/c3sc52368c] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
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36
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Hames MC, McFeeters H, Holloway WB, Stanley CB, Urban VS, McFeeters RL. Small molecule binding, docking, and characterization of the interaction between Pth1 and peptidyl-tRNA. Int J Mol Sci 2013; 14:22741-52. [PMID: 24256814 PMCID: PMC3856088 DOI: 10.3390/ijms141122741] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 10/31/2013] [Accepted: 11/12/2013] [Indexed: 01/13/2023] Open
Abstract
Bacterial Pth1 is essential for viability. Pth1 cleaves the ester bond between the peptide and nucleotide of peptidyl-tRNA generated from aborted translation, expression of mini-genes, and short ORFs. We have determined the shape of the Pth1:peptidyl-tRNA complex using small angle neutron scattering. Binding of piperonylpiperazine, a small molecule constituent of a combinatorial synthetic library common to most compounds with inhibitory activity, was mapped to Pth1 via NMR spectroscopy. We also report computational docking results, modeling piperonylpiperazine binding based on chemical shift perturbation mapping. Overall these studies promote Pth1 as a novel antibiotic target, contribute to understanding how Pth1 interacts with its substrate, advance the current model for cleavage, and demonstrate feasibility of small molecule inhibition.
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Affiliation(s)
- Mary C. Hames
- Department of Chemistry, University of Alabama in Huntsville, 301 Sparkman Drive, Huntsville, AL 35899, USA; E-Mails: (M.C.H.); (H.M.); (W.B.H.)
| | - Hana McFeeters
- Department of Chemistry, University of Alabama in Huntsville, 301 Sparkman Drive, Huntsville, AL 35899, USA; E-Mails: (M.C.H.); (H.M.); (W.B.H.)
| | - W. Blake Holloway
- Department of Chemistry, University of Alabama in Huntsville, 301 Sparkman Drive, Huntsville, AL 35899, USA; E-Mails: (M.C.H.); (H.M.); (W.B.H.)
| | - Christopher B. Stanley
- Oak Ridge National Laboratory, Biology and Soft Matter Division, P.O. Box 2008, Oak Ridge, TN 37831, USA; E-Mails: (C.B.S.); (V.S.U.)
| | - Volker S. Urban
- Oak Ridge National Laboratory, Biology and Soft Matter Division, P.O. Box 2008, Oak Ridge, TN 37831, USA; E-Mails: (C.B.S.); (V.S.U.)
| | - Robert L. McFeeters
- Department of Chemistry, University of Alabama in Huntsville, 301 Sparkman Drive, Huntsville, AL 35899, USA; E-Mails: (M.C.H.); (H.M.); (W.B.H.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-256-824-6023; Fax: +1-256-824-6349
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37
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Liberton M, Collins AM, Page LE, O'Dell WB, O'Neill H, Urban VS, Timlin JA, Pakrasi HB. Probing the consequences of antenna modification in cyanobacteria. Photosynth Res 2013; 118:17-24. [PMID: 24132812 DOI: 10.1007/s11120-013-9940-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 10/02/2013] [Indexed: 06/02/2023]
Abstract
Photosynthetic organisms rely on antenna systems to harvest and deliver energy from light to reaction centers. In fluctuating photic environments, regulation of light harvesting is critical for a photosynthetic organism's survival. Here, we describe the use of a suite of phycobilisome mutants to probe the consequences of antenna truncation in the cyanobacterium Synechocystis sp. PCC 6803. Studies using transmission electron microscopy (TEM), hyperspectral confocal fluorescence microscopy (HCFM), small-angle neutron scattering (SANS), and an optimized photobioreactor system have unraveled the adaptive strategies that cells employ to compensate for antenna reduction. As the phycobilisome antenna size decreased, changes in thylakoid morphology were more severe and physical segregation of the two photosystems increased. Repeating distances between thylakoid membranes measured by SANS were correlated with TEM data, and corresponded to the degree of phycobilisome truncation. Thylakoid membranes were found to have a high degree of structural flexibility, and changes in the membrane system upon illumination were rapid and reversible. Phycobilisome truncation in Synechocystis 6803 reduced the growth rate and lowered biomass accumulation. Together, these results lend a dynamic perspective to the intracellular membrane organization in cyanobacteria cells and suggest an adaptive mechanism that allows cells to adjust to altered light absorption capabilities, while highlighting the cell-wide implications of antenna truncation.
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Affiliation(s)
- Michelle Liberton
- Department of Biology, Washington University, One Brookings Drive, St. Louis, MO, 63130, USA
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38
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Liedel C, Schindler KA, Pavan MJ, Lewin C, Pester CW, Ruppel M, Urban VS, Shenhar R, Böker A. Electric-field-induced alignment of block copolymer/nanoparticle blends. Small 2013; 9:3276-3281. [PMID: 23495246 DOI: 10.1002/smll.201202380] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Revised: 12/13/2012] [Indexed: 06/01/2023]
Abstract
External electric fields readily align birefringent block-copolymer mesophases. In this study the effect of gold nanoparticles on the electric-field-induced alignment of a lamellae-forming polystyrene-block-poly(2-vinylpyridine) copolymer is assessed. Nanoparticles are homogeneously dispersed in the styrenic phase and promote the quantitative alignment of lamellar domains by substantially lowering the critical field strength above which alignment proceeds. The results suggest that the electric-field-assisted alignment of nanostructured block copolymer/nanoparticle composites may offer a simple way to greatly mitigate structural and orientational defects of such films under benign experimental conditions.
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Affiliation(s)
- Clemens Liedel
- Macromolecular Materials and Surfaces, RWTH Aachen University and DWI an der RWTH, Aachen e.V., Forckenbeckstraße 50, 52056 Aachen, Germany
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39
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Schoberth HG, Pester CW, Ruppel M, Urban VS, Böker A. Orientation-Dependent Order-Disorder Transition of Block Copolymer Lamellae in Electric Fields. ACS Macro Lett 2013; 2:469-473. [PMID: 35581799 DOI: 10.1021/mz400013u] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Electric fields have been shown to stabilize the disordered phase of near-critical block copolymer solutions. Here, we use in situ synchrotron small-angle X-ray scattering to examine how the initial orientation of lamellar domains with respect to the external field (φ) affects the shift in the order-disorder transition temperature (TODT) of lyotropic solutions of poly(styrene-b-isoprene) in toluene. We find a downward shift of the transition temperature, which scales with lamellar orientation as ΔTODT ∼ cos2 φ, in accordance with theory.
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Affiliation(s)
- Heiko G. Schoberth
- Lehrstuhl für Makromolekulare
Materialien und Oberflächen, DWI an der RWTH Aachen e.V., RWTH Aachen University, D-52056 Aachen, Germany
| | - Christian W. Pester
- Lehrstuhl für Makromolekulare
Materialien und Oberflächen, DWI an der RWTH Aachen e.V., RWTH Aachen University, D-52056 Aachen, Germany
| | - Markus Ruppel
- Chemical Sciences Division, Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee
37831, United States
| | - Volker S. Urban
- Biology
and Soft Matter Division, Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee
37831, United States
| | - Alexander Böker
- Lehrstuhl für Makromolekulare
Materialien und Oberflächen, DWI an der RWTH Aachen e.V., RWTH Aachen University, D-52056 Aachen, Germany
- JARA-FIT, RWTH Aachen University, D-52056 Aachen, Germany
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40
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Ruppel M, Pester CW, Langner KM, Sevink GJA, Schoberth HG, Schmidt K, Urban VS, Mays JW, Böker A. Electric field induced selective disordering in lamellar block copolymers. ACS Nano 2013; 7:3854-3867. [PMID: 23573901 DOI: 10.1021/nn3059604] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
External electric fields align nanostructured block copolymers by either rotation of grains or nucleation and growth depending on how strongly the chemically distinct block copolymer components are segregated. In close vicinity to the order-disorder transition, theory and simulations suggest a third mechanism: selective disordering. We present a time-resolved small-angle X-ray scattering study that demonstrates how an electric field can indeed selectively disintegrate ill-aligned lamellae in a lyotropic block copolymer solution, while lamellae with interfaces oriented parallel to the applied field prevail. The present study adds an additional mechanism to the experimentally corroborated suite of mechanistic pathways, by which nanostructured block copolymers can align with an electric field. Our results further unveil the benefit of electric field assisted annealing for mitigating orientational disorder and topological defects in block copolymer mesophases, both in close vicinity to the order-disorder transition and well below it.
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Affiliation(s)
- Markus Ruppel
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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41
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Liedel C, Pester CW, Ruppel M, Lewin C, Pavan MJ, Urban VS, Shenhar R, Bösecke P, Böker A. Block Copolymer Nanocomposites in Electric Fields: Kinetics of Alignment. ACS Macro Lett 2013; 2:53-58. [PMID: 35581825 DOI: 10.1021/mz3005132] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We investigate the kinetics of block copolymer/nanoparticle composite alignment in an electric field using in situ transmission small-angle X-ray scattering. As a model system, we employ a lamellae forming polystyrene-block-poly(2-vinyl pyridine) block copolymer with different contents of gold nanoparticles in thick films under solvent vapor annealing. While the alignment improves with increasing nanoparticle fraction, the kinetics slows down. This is explained by changes in the degree of phase separation and viscosity. Our findings provide extended insights into the basics of nanocomposite alignment.
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Affiliation(s)
- Clemens Liedel
- Macromolecular Materials
and Surfaces, RWTH Aachen University and DWI an der RWTH Aachen e.V., Forckenbeckstraße
50, 52056 Aachen, Germany
| | - Christian W. Pester
- Macromolecular Materials
and Surfaces, RWTH Aachen University and DWI an der RWTH Aachen e.V., Forckenbeckstraße
50, 52056 Aachen, Germany
| | - Markus Ruppel
- Chemical Sciences
Division, Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee 37831, United States
| | - Christian Lewin
- Macromolecular Materials
and Surfaces, RWTH Aachen University and DWI an der RWTH Aachen e.V., Forckenbeckstraße
50, 52056 Aachen, Germany
| | - Mariela J. Pavan
- Institute of Chemistry, and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
| | - Volker S. Urban
- Biology and Soft
Matter Division, Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee 37831, United States
| | - Roy Shenhar
- Institute of Chemistry, and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
| | - Peter Bösecke
- European Synchrotron Radiation Facility (ESRF), 6 rue Jules Horowitz, 38043
Grenoble Cedex, France
| | - Alexander Böker
- Macromolecular Materials
and Surfaces, RWTH Aachen University and DWI an der RWTH Aachen e.V., Forckenbeckstraße
50, 52056 Aachen, Germany
- JARA-FIT, RWTH Aachen University, 52056 Aachen, Germany
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Dergunov SA, Richter AG, Kim MD, Pingali SV, Urban VS, Pinkhassik E. Synergistic self-assembly of scaffolds and building blocks for directed synthesis of organic nanomaterials. Chem Commun (Camb) 2013; 49:11026-8. [DOI: 10.1039/c3cc45847d] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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43
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Chaudhuri BN, Qian S, Urban VS, Dean R. Structural Organization of the Mycobacterial Segrosome. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.1024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Qian S, Dean R, Urban VS, Chaudhuri BN. The internal organization of mycobacterial partition assembly: does the DNA wrap a protein core? PLoS One 2012; 7:e52690. [PMID: 23285150 PMCID: PMC3527565 DOI: 10.1371/journal.pone.0052690] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 11/20/2012] [Indexed: 11/18/2022] Open
Abstract
Before cell division in many bacteria, the ParBs spread on a large segment of DNA encompassing the origin-proximal parS site(s) to form the partition assembly that participates in chromosome segregation. Little is known about the structural organization of chromosomal partition assembly. We report solution X-ray and neutron scattering data characterizing the size parameters and internal organization of a nucleoprotein assembly formed by the mycobacterial chromosomal ParB and a 120-meric DNA containing a parS-encompassing region from the mycobacterial genome. The cross-sectional radii of gyration and linear mass density describing the rod-like ParB-DNA assembly were determined from solution scattering. A "DNA outside, protein inside" mode of partition assembly organization consistent with the neutron scattering hydrogen/deuterium contrast variation data is discussed. In this organization, the high scattering DNA is positioned towards the outer region of the partition assembly. The new results presented here provide a basis for understanding how ParBs organize the parS-proximal chromosome, thus setting the stage for further interactions with the DNA condensins, the origin tethering factors and the ParA.
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Affiliation(s)
- Shuo Qian
- Center for Structural Molecular Biology, Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - Rebecca Dean
- Hauptman Woodward Institute, Buffalo, New York, United States of America
| | - Volker S. Urban
- Center for Structural Molecular Biology, Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - Barnali N. Chaudhuri
- Hauptman Woodward Institute, Buffalo, New York, United States of America
- Department of Structural Biology, State University of New York, Buffalo, New York, United States of America
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45
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Liberton M, Page LE, O'Dell WB, O'Neill H, Mamontov E, Urban VS, Pakrasi HB. Organization and flexibility of cyanobacterial thylakoid membranes examined by neutron scattering. J Biol Chem 2012; 288:3632-40. [PMID: 23255600 DOI: 10.1074/jbc.m112.416933] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cyanobacteria are prokaryotes that can use photosynthesis to convert sunlight into cellular fuel. Knowledge of the organization of the membrane systems in cyanobacteria is critical to understanding the metabolic processes in these organisms. We examined the wild-type strain of Synechocystis sp. PCC 6803 and a series of mutants with altered light-harvesting phycobilisome antenna systems for changes in thylakoid membrane architecture under different conditions. Using small-angle neutron scattering, it was possible to resolve correlation distances of subcellular structures in live cells on the nanometer scale and capture dynamic light-induced changes to these distances. Measurements made from samples with varied scattering contrasts confirmed that these distances could be attributed to the thylakoid lamellar system. We found that the changes to the thylakoid system were reversible between light- and dark-adapted states, demonstrating a robust structural flexibility in the architecture of cyanobacterial cells. Chemical disruption of photosynthetic electron transfer diminished these changes, confirming the involvement of the photosynthetic apparatus. We have correlated these findings with electron microscopy data to understand the origin of the changes in the membranes and found that light induces an expansion in the center-to-center distances between the thylakoid membrane layers. These combined data lend a dynamic dimension to the intracellular organization in cyanobacterial cells.
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Affiliation(s)
- Michelle Liberton
- Department of Biology, Washington University, St. Louis, Missouri 63130, USA
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46
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Wignall GD, Littrell KC, Heller WT, Melnichenko YB, Bailey KM, Lynn GW, Myles DA, Urban VS, Buchanan MV, Selby DL, Butler PD. The 40 m general purpose small-angle neutron scattering instrument at Oak Ridge National Laboratory. J Appl Crystallogr 2012. [DOI: 10.1107/s0021889812027057] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023] Open
Abstract
A series of upgrades have been undertaken at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, including the installation of a supercritical hydrogen moderator (T≃ 20 K), which has boosted the flux of long-wavelength neutrons by over two orders of magnitude. In order to take advantage of the new capabilities, a 40 m-long small-angle neutron scattering (SANS) instrument has been constructed, which utilizes a mechanical velocity selector, pinhole collimation and a high-count-rate (>105 Hz) large-area (1 m2) two-dimensional position-sensitive detector. The incident wavelength (λ), resolution (Δλ/λ), incident collimation and sample-to-detector distance are independently variable under computer control. The detector can be moved up to 45 cm off-axis to increase the overallQrange [<0.001 <Q= (4π/λ)sinθ < 1 Å−1, where 2θ is the angle of scatter]. The design and characteristics of this instrument are described, along with examples of scattering data to illustrate the performance.
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Langan P, Evans BR, Foston M, Heller WT, O'Neill H, Petridis L, Pingali SV, Ragauskas AJ, Smith JC, Urban VS, Davison BH. Neutron Technologies for Bioenergy Research. Ind Biotechnol (New Rochelle N Y) 2012. [DOI: 10.1089/ind.2012.0012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Paul Langan
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN
- Center for Structural Molecular Biology, Oak Ridge National Laboratory, Oak Ridge, TN
| | - Barbara R. Evans
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN
| | - Marcus Foston
- Institute of Paper Science and Technology, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA
| | - William T. Heller
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN
| | - Hugh O'Neill
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN
- Center for Structural Molecular Biology, Oak Ridge National Laboratory, Oak Ridge, TN
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN
| | - Loukas Petridis
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN
- Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN
| | - Sai Venkatesh Pingali
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN
- Center for Structural Molecular Biology, Oak Ridge National Laboratory, Oak Ridge, TN
| | - Arthur J. Ragauskas
- Institute of Paper Science and Technology, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA
| | - Jeremy C. Smith
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN
- Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN
- UT/ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, TN
| | - Volker S. Urban
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN
- Center for Structural Molecular Biology, Oak Ridge National Laboratory, Oak Ridge, TN
| | - Brian H. Davison
- Bioscience Division, Oak Ridge National Laboratory, Oak Ridge, TN
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48
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Harton SE, Pingali SV, Nunnery GA, Baker DA, Walker SH, Muddiman DC, Koga T, Rials TG, Urban VS, Langan P. Evidence for Complex Molecular Architectures for Solvent-Extracted Lignins. ACS Macro Lett 2012; 1:568-573. [PMID: 35607063 DOI: 10.1021/mz300045e] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Lignin, an abundant, naturally occurring biopolymer, is often considered "waste" and used as a simple fuel source in the paper-making process. However, lignin has emerged as a promising renewable resource for engineering materials, such as carbon fibers. Unfortunately, the molecular architecture of lignin (in vivo and extracted) is still elusive, with numerous conflicting reports in the literature, and knowledge of this structure is extremely important, not only for materials technologies, but also for production of biofuels such as cellulosic ethanol due to biomass recalcitrance. As such, the molecular structures of solvent-extracted (sulfur-free) lignins, which have been modified using various acyl chlorides, have been probed using small-angle X-ray (SAXS) and neutron (SANS) scattering in tetrahydrofuran (THF) solution along with hydrodynamic characterization using dilute solution viscometry and gel permeation chromatography (GPC) in THF. Mass spectrometry shows an absolute molecular weight ≈18-30 kDa (≈80-140 monomers), while GPC shows a relative molecular weight ∼3 kDa. A linear styrene oligomer (2.5 kDa) was also analyzed in THF using SANS. Results clearly show that lignin molecular architectures are somewhat rigid and complex, ranging from nanogels to hyperbranched macromolecules, not linear oligomers or physical assemblies of oligomers, which is consistent with previously proposed delignification (extraction) mechanisms. Future characterization using the methods discussed here can be used to guide extraction processes as well as genetic engineering technologies to convert lignin into value added materials with the potential for high positive impact on global sustainability.
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Affiliation(s)
| | | | | | - Darren A. Baker
- Center for Renewable
Carbon, The University of Tennessee, Knoxville, Tennessee, 37996, United States
| | - S. Hunter Walker
- Department of Chemistry, North Carolina State University, Raleigh,
North Carolina 27695, United States
| | - David C. Muddiman
- Department of Chemistry, North Carolina State University, Raleigh,
North Carolina 27695, United States
| | - Tadanori Koga
- Chemical and Molecular Engineering
Program, Department of Materials Science and Engineering, Stony Brook University, Stony Brook,
New York, 11794, United States
| | - Timothy G. Rials
- Center for Renewable
Carbon, The University of Tennessee, Knoxville, Tennessee, 37996, United States
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49
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Liedel C, Pester CW, Ruppel M, Urban VS, Böker A. Macromol. Chem. Phys. 3/2012. MACROMOL CHEM PHYS 2012. [DOI: 10.1002/macp.201290009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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50
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O'Dell WB, Beatty KJ, Kuo-Hsiang Tang J, Blankenship RE, Urban VS, O'Neill H. Sol–gel entrapped light harvesting antennas: immobilization and stabilization of chlorosomes for energy harvesting. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm34357f] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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