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Interaction of amphiphilic lipoarabinomannan with host carrier lipoproteins in tuberculosis patients: Implications for blood-based diagnostics. PLoS One 2021; 16:e0243337. [PMID: 33826643 PMCID: PMC8026062 DOI: 10.1371/journal.pone.0243337] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 03/01/2021] [Indexed: 11/18/2022] Open
Abstract
Lipoarabinomannan (LAM), an amphiphilic lipoglycan of the Mycobacterium tuberculosis cell wall, is a diagnostic target for tuberculosis. Previous work from our laboratory and others suggests that LAM is associated with host serum lipoproteins, which may in turn have implications for diagnostic assays. Our team has developed two serum assays for amphiphile detection: lipoprotein capture and membrane insertion. The lipoprotein capture assay relies on capture of the host lipoproteins, exploiting the biological association of host lipoprotein with microbial amphiphilic biomarkers to "concentrate" LAM. In contrast, the membrane insertion assay is independent of the association between pathogen amphiphiles and host lipoprotein association, and directly captures LAM based on its thermodynamic propensity for association with a supported lipid membrane, which forms the functional surface of an optical biosensor. In this manuscript, we explored the use of these assays for the detection of LAM in sera from adults whose tuberculosis status had been well-characterized using conventional microbiological tests, and endemic controls. Using the lipoprotein capture assay, LAM signal/noise ratios were >1.0 in 29/35 (83%) individuals with culture-confirmed active tuberculosis, 8/13 (62%) individuals with tuberculosis symptoms, but no positive culture for M. tuberculosis, and 0/6 (0%) symptom-free endemic controls. To evaluate serum LAM levels without bias associated with potential differences in circulating host lipoprotein concentrations between individuals, we subsequently processed available samples to liberate LAM from associated host lipoprotein assemblies followed by direct detection of the pathogen biomarker using the membrane insertion approach. Using the membrane insertion assay, signal/noise for detection of serum LAM was greater than that observed using the lipoprotein capture method for culture-confirmed TB patients (6/6), yet remained negative for controls (2/2). Taken together, these results suggest that detection of serum LAM is a promising TB diagnostic approach, but that further work is required to optimize assay performance and to decipher the implications of LAM/host lipoprotein associations for diagnostic assay performance and TB pathogenesis.
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Understanding the Significance of Biochemistry in the Storage, Handling, Purification, and Sampling of Amphiphilic Mycolactone. Toxins (Basel) 2019; 11:toxins11040202. [PMID: 30987300 PMCID: PMC6520765 DOI: 10.3390/toxins11040202] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 02/26/2019] [Accepted: 04/01/2019] [Indexed: 12/29/2022] Open
Abstract
Mycolactone, the amphiphilic macrolide toxin secreted by Mycobacterium ulcerans, plays a significant role in the pathology and manifestations of Buruli ulcer (BU). Consequently, it follows that the toxin is a suitable target for the development of diagnostics and therapeutics for this disease. Yet, several challenges have deterred such development. For one, the lipophilic nature of the toxin makes it difficult to handle and store and contributes to variability associated with laboratory experimentation and purification yields. In this manuscript, we have attempted to incorporate our understanding of the lipophilicity of mycolactone in order to define the optimal methods for the storage, handling, and purification of this toxin. We present a systematic correlation of variability associated with measurement techniques (thin-layer chromatography (TLC), mass spectrometry (MS), and UV-Vis spectrometry), storage conditions, choice of solvents, as well as the impact of each of these on toxin function as assessed by cellular cytotoxicity. We also compared natural mycolactone extracted from bacterial culture with synthesized toxins in laboratory (solvents, buffers) and physiologically relevant (serum) matrices. Our results point to the greater stability of mycolactone in organic, as well as detergent-containing, solvents, regardless of the container material (plastic, glass, or silanized tubes). They also highlight the presence of toxin in samples that may be undetectable by any one technique, suggesting that each detection approach captures different configurations of the molecule with varying specificity and sensitivity. Most importantly, our results demonstrate for the very first time that amphiphilic mycolactone associates with host lipoproteins in serum, and that this association will likely impact our ability to study, diagnose, and treat Buruli ulcers in patients.
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Abstract
Early and rapid detection of bovine tuberculosis (bTB) is critical to controlling the spread of this disease in cattle and other animals. In this study, we demonstrate the development of an immunoassay for the direct detection of the bovine bTB biomarker, lipomannan (LM) in serum using a waveguide-based optical biosensor. We apply an ultra-sensitive detection strategy developed by our team, termed lipoprotein capture, that exploits the pull-down of high-density lipoprotein (HDL) nanodiscs from cattle blood that allows for the recovery and detection of associated LM. We also profile the change in the expression of these TB biomarkers as a function of time from a small set of samples collected from studies of bovine TB-infected cattle. We demonstrate for the first time the direct detection of bovine LM in serum, and clearly show that the biomarker is expressed in detectable concentrations during the entire course of the infection.
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Beyond Helper Phage: Using "Helper Cells" to Select Peptide Affinity Ligands. PLoS One 2016; 11:e0160940. [PMID: 27626637 PMCID: PMC5023105 DOI: 10.1371/journal.pone.0160940] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 07/27/2016] [Indexed: 12/16/2022] Open
Abstract
Peptides are important affinity ligands for microscopy, biosensing, and targeted delivery. However, because they can have low affinity for their targets, their selection from large naïve libraries can be challenging. When selecting peptidic ligands from display libraries, it is important to: 1) ensure efficient display; 2) maximize the ability to select high affinity ligands; and 3) minimize the effect of the display context on binding. The “helper cell” packaging system has been described as a tool to produce filamentous phage particles based on phagemid constructs with varying display levels, while remaining free of helper phage contamination. Here we report on the first use of this system for peptide display, including the systematic characterization and optimization of helper cells, their inefficient use in antibody display and their use in creating and selecting from a set of phage display peptide libraries. Our libraries were analyzed with unprecedented precision by standard or deep sequencing, and shown to be superior in quality than commercial gold standards. Using our helper cell libraries, we have obtained ligands recognizing Yersinia pestis surface antigen F1V and L-glutamine-binding periplasmic protein QBP. In the latter case, unlike any of the peptide library selections described so far, we used a combination of phage and yeast display to select intriguing peptide ligands. Based on the success of our selections we believe that peptide libraries obtained with helper cells are not only suitable, but preferable to traditional phage display libraries for selection of peptidic ligands.
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Taste of sugar at the membrane: thermodynamics and kinetics of the interaction of a disaccharide with lipid bilayers. Biophys J 2013; 104:622-32. [PMID: 23442913 DOI: 10.1016/j.bpj.2012.12.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Revised: 12/03/2012] [Accepted: 12/05/2012] [Indexed: 11/29/2022] Open
Abstract
Sugar recognition at the membrane is critical in various physiological processes. Many aspects of sugar-membrane interaction are still unknown. We take an integrated approach by combining conventional molecular-dynamics simulations with enhanced sampling methods and analytical models to understand the thermodynamics and kinetics of a di-mannose molecule in a phospholipid bilayer system. We observe that di-mannose has a slight preference to localize at the water-phospholipid interface. Using umbrella sampling, we show the free energy bias for this preferred location to be just -0.42 kcal/mol, which explains the coexistence of attraction and exclusion mechanisms of sugar-membrane interaction. Accurate estimation of absolute entropy change of water molecules with a two-phase model indicates that the small energy bias is the result of a favorable entropy change of water molecules. Then, we incorporate results from molecular-dynamics simulation in two different ways to an analytical diffusion-reaction model to obtain association and dissociation constants for di-mannose interaction with membrane. Finally, we verify our approach by predicting concentration dependence of di-mannose recognition at the membrane that is consistent with experiment. In conclusion, we provide a combined approach for the thermodynamics and kinetics of a weak ligand-binding system, which has broad implications across many different fields.
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Association of lipoarabinomannan with high density lipoprotein in blood: implications for diagnostics. Tuberculosis (Edinb) 2013; 93:301-7. [PMID: 23507184 DOI: 10.1016/j.tube.2013.02.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2012] [Revised: 02/11/2013] [Accepted: 02/14/2013] [Indexed: 11/27/2022]
Abstract
Understanding the pathophysiology of tuberculosis, and the bio-distribution of pathogen-associated molecules in the host is essential for the development of efficient methods of intervention. One of the key virulence factors in the pathology of tuberculosis infection is Lipoarabinomannan (LAM). Previously, we have demonstrated the reliable detection of LAM in urine from tuberculosis patients in a sandwich immunoassay format. We have also applied an ultra-sensitive detection strategy developed for amphiphilic biomarkers, membrane insertion, to the detection of LAM with a limit of detection of 10 fM. Herein, we evaluate the application of membrane insertion to the detection of LAM in patient serum, and demonstrate that the circulating concentrations of 'monomeric' LAM in serum are very low, despite significantly higher concentrations in the urine. Using spiked samples, we demonstrate that this discrepancy is due to the association of LAM with high-density lipoprotein (HDL) nanodiscs in human serum. Indeed, pull-down of HDL nanodiscs from human serum allows for the recovery of HDL-associated LAM. These studies suggest that LAM is likely associated with carrier molecules such as HDL in the blood of patients infected with tuberculosis. This phenomenon may not be limited to LAM in that many pathogen-associated molecular patterns like LAM are amphiphilic in nature and may also be associated with host lipid carriers. Such interactions are likely to affect host-pathogen interactions, pathogen bio-distribution and clearance in the host, and must be thoroughly understood for the effective design of vaccines and diagnostics.
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Rapid detection of Mycobacterium tuberculosis biomarkers in a sandwich immunoassay format using a waveguide-based optical biosensor. Tuberculosis (Edinb) 2012; 92:407-16. [PMID: 22710249 DOI: 10.1016/j.tube.2012.05.009] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Revised: 05/21/2012] [Accepted: 05/22/2012] [Indexed: 10/28/2022]
Abstract
Early diagnosis of active tuberculosis (TB) remains an elusive challenge, especially in individuals with disseminated TB and HIV co-infection. Recent studies have shown a promise for the direct detection of pathogen-specific biomarkers such as lipoarabinomannan (LAM) for the diagnosis of TB in HIV-positive individuals. Currently, traditional immunoassay platforms that suffer from poor sensitivity and high non-specific interactions are used for the detection of such biomarkers. In this manuscript, we demonstrate the development of sandwich immunoassays for the direct detection of three TB-specific biomarkers, namely LAM, early secretory antigenic target 6 (ESAT6) and antigen 85 complex (Ag85), using a waveguide-based optical biosensor platform. Combining detection within the evanescent field of a planar optical waveguide with functional surfaces that reduce non-specific interactions allows for the ultra-sensitive and quantitative detection of biomarkers (an order of magnitude enhanced sensitivity, as compared to plate-based ELISA) in complex patient samples (urine, serum) within a short time. We also demonstrate the detection of LAM in urine from a small sample of subjects being treated for TB using this approach with excellent sensitivity and 100% corroboration with disease status. These results suggest that pathogen-specific biomarkers can be applied for the rapid and effective diagnosis of disease. It is likely that detection of a combination of biomarkers offers greater reliability of diagnosis, rather than detection of any single pathogen biomarker. NCT00341601.
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Quantitative multiplex detection of pathogen biomarkers on multichannel waveguides. Anal Chem 2010; 82:136-44. [PMID: 20000585 DOI: 10.1021/ac901497g] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
No single biomarker can accurately predict disease. An ideal biodetection technology should be capable of the quantitative, reproducible, and sensitive detection of a limited suite of such molecules. To this end, we have developed a multiplex biomarker assay for protective antigen and lethal factor of the Bacillus anthracis lethal toxin using semiconductor quantum dots as the fluorescence reporters on our waveguide-based biosensor platform. The platform is extendable to a wide array of biomarkers, facilitating rapid, quantitative, sensitive, and multiplex detection, better than achievable by conventional immunoassay. Our assay allows for the sensitive (limit of detection 1 pM each), specific (minimal nonspecific binding), and rapid (15 min) detection of these biomarkers in complex biological samples (e.g., serum). To address the issue of reproducibility in measurement and to increase our sample throughput, we have incorporated multichannel waveguides capable of simultaneous multiplex detection of biomarkers in three samples in quadruplicate. In this paper, we present the design, fabrication, and development of multichannel waveguides for the simultaneous detection of lethal factor and protective antigen in serum. Evaluation of the multichannel waveguide shows an excellent concordance with single-channel data and effective, simultaneous, and reproducible measurement of lethal toxins in three samples.
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Waveguide-based biosensors for pathogen detection. SENSORS (BASEL, SWITZERLAND) 2009; 9:5783-809. [PMID: 22346727 PMCID: PMC3274158 DOI: 10.3390/s90705783] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/04/2009] [Revised: 07/13/2009] [Accepted: 07/13/2009] [Indexed: 11/16/2022]
Abstract
Optical phenomena such as fluorescence, phosphorescence, polarization, interference and non-linearity have been extensively used for biosensing applications. Optical waveguides (both planar and fiber-optic) are comprised of a material with high permittivity/high refractive index surrounded on all sides by materials with lower refractive indices, such as a substrate and the media to be sensed. This arrangement allows coupled light to propagate through the high refractive index waveguide by total internal reflection and generates an electromagnetic wave-the evanescent field-whose amplitude decreases exponentially as the distance from the surface increases. Excitation of fluorophores within the evanescent wave allows for sensitive detection while minimizing background fluorescence from complex, "dirty" biological samples. In this review, we will describe the basic principles, advantages and disadvantages of planar optical waveguide-based biodetection technologies. This discussion will include already commercialized technologies (e.g., Corning's EPIC(®) Ô, SRU Biosystems' BIND(™), Zeptosense(®), etc.) and new technologies that are under research and development. We will also review differing assay approaches for the detection of various biomolecules, as well as the thin-film coatings that are often required for waveguide functionalization and effective detection. Finally, we will discuss reverse-symmetry waveguides, resonant waveguide grating sensors and metal-clad leaky waveguides as alternative signal transducers in optical biosensing.
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An intrinsically fluorescent recognition ligand scaffold based on chaperonin protein and semiconductor quantum-dot conjugates. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2009; 5:1036-1042. [PMID: 19334012 DOI: 10.1002/smll.200801106] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Genetic engineering of a novel protein-nanoparticle hybrid system with great potential for biosensing applications and for patterning of various types of nanoparticles is described. The hybrid system is based on a genetically modified chaperonin protein from the hyperthermophilic archaeon Sulfolobus shibatae. This chaperonin is an 18-subunit double ring, which self-assembles in the presence of Mg ions and ATP. Described here is a mutant chaperonin (His-beta-loopless, HBLL) with increased access to the central cavity and His-tags on each subunit extending into the central cavity. This mutant binds water-soluble semiconductor quantum dots, creating a protein-encapsulated fluorescent nanoparticle. The new bioconjugate has high affinity, in the order of strong antibody-antigen interactions, a one-to-one protein-nanoparticle stoichiometry, and high stability. By adding selective binding sites to the solvent-exposed regions of the chaperonin, this protein-nanoparticle bioconjugate becomes a sensor for specific targets.
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Optimizing a Waveguide-Based Sandwich Immunoassay for Tumor Biomarkers: Evaluating Fluorescent Labels and Functional Surfaces. Bioconjug Chem 2009; 20:222-30. [DOI: 10.1021/bc800283e] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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12
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Detection of Intact Influenza Viruses using Biotinylated Biantennary S-Sialosides. J Am Chem Soc 2008; 130:8169-71. [DOI: 10.1021/ja800842v] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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13
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Functional PEG-modified thin films for biological detection. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:2240-2247. [PMID: 18229965 DOI: 10.1021/la7033438] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We report a general procedure to prepare functional organic thin films for biological assays on oxide surfaces. Silica surfaces were functionalized by self-assembly of an amine-terminated silane film using both vapor- and solution-phase deposition of 3'-aminopropylmethyldiethoxysilane (APMDES). We found that vapor-phase deposition of APMDES under reduced pressure produced the highest quality monolayer films with uniform surface coverage, as determined by atomic force microscopy (AFM), ellipsometry, and contact angle measurements. The amine-terminated films were chemically modified with a mixture of carboxylic acid-terminated poly(ethylene glycol) (PEG) chains of varying functionality. A fraction of the PEG chains (0.1-10 mol %) terminated in biotin, which produced a surface with an affinity toward streptavidin. When used in pseudo-sandwich assays on waveguide platforms for the detection of Bacillus anthracis protective antigen (PA), these functional PEG surfaces significantly reduced nonspecific binding to the waveguide surface while allowing for highly specific binding. Detection of PA was used to validate these films for sensing applications in both buffer and complex media. Ultimately, these results represent a step toward the realization of a robust, reusable, and autonomous biosensor.
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Luminescence Excitation Spectroscopy in Poly(p-Phenylene-Vinylene) Derivatives: Implications for a Semiconductor Band VS. Exciton Model in Conjugated Polymers. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/10587259408039282] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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15
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Optical Studies of Polyphenylenevinylene and Derivatives: Raman and Luminescence Spectroscopy. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/10587259408039239] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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16
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Neutron reflectivity study of lipid membranes assembled on ordered nanocomposite and nanoporous silica thin films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:2865-2870. [PMID: 15779959 DOI: 10.1021/la0471240] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Single bilayer membranes of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) were formed on ordered nanocomposite and nanoporous silica thin films by fusion of small unilamellar vesicles. The structure of these membranes was investigated using neutron reflectivity. The underlying thin films were formed by evaporation induced self-assembly to obtain periodic arrangements of silica and surfactant molecules in the nanocomposite thin films, followed by photocalcination to oxidatively remove the organics and render the films nanoporous. We show that this platform affords homogeneous and continuous bilayer membranes that have promising applications as model membranes and sensors.
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Single-crystal polarized Raman scattering and vibrational assignments for dicesium lithium metal hexacyanides, Cs2LiM(CN)6 (M = chromium, manganese, iron, cobalt, rhodium, iridium). Inorg Chem 2002. [DOI: 10.1021/ic50132a013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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21
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Effects of temperature on the crystal and molecular structure of the mixed-valence linear chain bis(ethylenediamine)platinum bis(ethylenediamine)dihaloplatinum tetraperchlorate (halo = chloro, bromo). Inorg Chem 2002. [DOI: 10.1021/ic00062a044] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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22
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23
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24
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Interpretation of potential constants: application to study of bonding forces in metal cyanide complexes and metal carbonyls. Acc Chem Res 2002. [DOI: 10.1021/ar50100a002] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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25
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26
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Aspects of the structure and bonding in Prussian Blues. Single-crystal Raman study of trimanganese hexacyanocobaltate hydrate (Mn3[Co(CN)6].xH2O) and tricadmium bis(hexacyanocobaltate) hydrate (Cd3[Co(CN)6]2.xH2O). Inorg Chem 2002. [DOI: 10.1021/ic50156a002] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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27
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28
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Near-infrared-excitation resonance Raman spectra of the primary electron donor in photosynthetic reaction centers from Rhodobacter sphaeroides. J Am Chem Soc 2002. [DOI: 10.1021/ja00174a044] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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29
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Transverse optical to longitudinal optical splitting and dipole moment derivatives from infrared spectra of thin films of molecular solids. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100160a016] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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30
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Orientational ordering and site-selective photochemistry of uranium hexafluoride isolated in argon matrixes. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j150651a008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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31
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Pressure dependence of the electronic spectra of quasi-one-dimensional Pt2X semiconductors. J Am Chem Soc 2002. [DOI: 10.1021/ja00183a012] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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32
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Effects of outer-sphere electron transfer on the vibrational spectrum of dicesium antimony hexachloride. J Am Chem Soc 2002. [DOI: 10.1021/ja00401a003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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33
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Resonance Raman spectroscopy of metalloproteins under extreme conditions: cryogenic diamond-cell study of azurin. J Am Chem Soc 2002. [DOI: 10.1021/ja00309a054] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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34
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Structure and bonding in transition-metal carbonyls and nitrosyls. 1. Gas-phase electron-diffraction investigations of tetranitrosylchromium (Cr(NO)4, carbonyltrinitrosylmanganese (MnCO(NO)3), and dicarbonyldinitrosyliron (Fe(CO)2(NO)2). Inorg Chem 2002. [DOI: 10.1021/ic00212a012] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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35
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Studies of mixed-valence linear-chain complexes crystallized at elevated pressures. Crystal structures of bis(ethylenediamine)platinum bis(ethylenediamine)dihaloplatinum tetraperchlorate (halo = bromo, iodo). Inorg Chem 2002. [DOI: 10.1021/ic00330a016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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36
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Translational symmetries in the linear-chain semiconductors K4[Pt2(P2O5H2)4X].cntdot.nH2O (X = Cl, Br, I). J Am Chem Soc 2002. [DOI: 10.1021/ja00212a025] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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37
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Cryoresonance Raman spectroscopy of plastocyanin, azurin, and stellacyanin. A reevaluation of the identity of the resonance-enhanced modes. J Am Chem Soc 2002. [DOI: 10.1021/ja00341a075] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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38
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Molecular hydrogen complexes of the transition metals. 4. Preparation and characterization of M(CO)3(PR3)2(.eta.2-H2) (M = molybdenum, tungsten) and evidence for equilibrium dissociation of the H-H bond to give MH2(CO)3(PR3)2. J Am Chem Soc 2002. [DOI: 10.1021/ja00282a026] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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39
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40
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Femtosecond vibrational dynamics of self-trapping in a quasi-one-dimensional system. PHYSICAL REVIEW LETTERS 2000; 84:4425-8. [PMID: 10990702 DOI: 10.1103/physrevlett.84.4425] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/1999] [Indexed: 05/17/2023]
Abstract
We have directly time resolved the lattice motions associated with the formation of the self-trapped exciton in the quasi-one-dimensional system [Pt(en)(2)] [Pt(en)2Br2];(PF6)(4) ( en = ethylene-diamine, C2H8N2), using femtosecond impulsive excitation techniques. A strongly damped, low-frequency wave packet modulation at approximately 110 cm(-1) accompanies the formation of the self-trapped exciton on a approximately 200 fs time scale following excitation of the intervalence charge-transfer transition. Coherent oscillations at the ground state vibrational frequency and its harmonics are also detected.
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Phase Behavior of a Structurally Constrained Organic−Inorganic Crystal: Temperature-Dependent Infrared Spectroscopy of Silver n-Dodecanethiolate. J Phys Chem B 1999. [DOI: 10.1021/jp992156v] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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42
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Integrated optical biosensor for detection of multivalent proteins. OPTICS LETTERS 1999; 24:1723-1725. [PMID: 18079915 DOI: 10.1364/ol.24.001723] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We have developed a simple, highly sensitive and specific optical waveguide sensor for the detection of multivalent proteins. The optical biosensor is based on optically tagged glycolipid receptors embedded within a fluid phospholipid bilayer membrane formed upon the surface of a planar optical waveguide. Binding of multivalent cholera toxin triggers a fluorescence resonance energy transfer that results in a two-color optical change that is monitored by measurement of emitted luminescence above the waveguide surface. The sensor approach is highly sensitive and specific and requires no additional reagents and washing steps. Demonstration of protein-receptor recognition by use of planar optical waveguides provides a path forward for the development of fieldable miniaturized biosensor arrays.
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Preparation and Spectroscopic Characterization of [Pt(en)2I2][Pt(CN)4]: A New Quasi-One-Dimensional Mixed Valence Chain Material in a Completely Ordered Lattice. J Phys Chem B 1999. [DOI: 10.1021/jp990460i] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Direct, ultrasensitive, and selective optical detection of protein toxins using multivalent interactions. Anal Chem 1999; 71:2097-107. [PMID: 10366891 DOI: 10.1021/ac981145f] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Three highly sensitive, selective, and reagent-free optical signal transduction methods for detection of polyvalent proteins have been developed by directly coupling distance-dependent fluorescence self-quenching and/or resonant-energy transfer to the protein-receptor binding events. The ganglioside GM1, as the recognition unit for cholera toxin (CT), was covalently labeled with fluorophores and then incorporated into a biomimetic membrane surface. The presence of CT with five binding sites for GM1 causes dramatic change for the fluorescence of the labeled GM1. (1) In the scheme using fluorescence self-quenching as a signal-transduction mechanism, the fluorescence intensity drops significantly as a result of aggregation of the fluorophore-labeled GM1 on a biomimetic surface. (2) By labeling GM1 with a fluorescence energy transfer pair, aggregation of the labeled GM1 results in a decrease in donor fluorescence and an increase in acceptor fluorescence, providing a unique signature for selective protein-receptor binding. (3) In the third scheme, using the biomimetic surface as part of signal transduction and combining both fluorescence self-quenching and energy-transfer mechanisms to enhance the signal transduction, a signal amplification was achieved. The detection systems can reliably detect less than 0.05 nM CT with fast response (less than 5 min). This approach can easily be adapted to any biosensor scheme that relies on multiple receptors or co-receptors. The methods can also be applied to investigate the kinetics and thermodynamics of the multivalent interactions.
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Abstract
In trial 1, 30 midlactation (213 d in milk) Holstein cows were randomly assigned to a control or enzyme treatment in a two-period crossover design and were fed a total mixed ration based on alfalfa hay and silage. Cows on the enzyme treatment received an enzyme solution containing cellulases and xylanases, which was sprayed on the forage component of the ration at a rate of 1.65 ml/kg of forage dry matter (DM) between 8 and 24 h prior to feeding. Cows consuming the forage treated with enzyme produced more milk (27.2 vs. 25.9 kg/d) and digested more DM per day than did cows fed the control forage. In trial 2, 40 early lactation Holstein cows were assigned to one of four treatments for 16 wk. Following a 2-wk covariate period, cows were assigned to 1) no enzyme treatment, 2) a low (1.25 ml/kg of forage DM) enzyme treatment, 3) a medium (2.5 ml/kg of forage DM) enzyme treatment, or 4) a high (5.0 ml/kg of forage DM) enzyme treatment. Enzymes were a 2:1 combination of cellulase and xylanase diluted in water and sprayed on a combination of alfalfa hay and silage and whole cottonseed immediately before mixing with a concentrate based on barley. Dry matter intakes were similar for cows on treatments 2, 3, and 4 and were greater than those for cows on treatment 1. Production of milk, 3.5% fat-corrected milk, and energy-corrected milk was greater for cows on treatment 3 than for cows on treatment 1. Fibrolytic enzymes applied to the forage portion of the rations prior to feeding improved lactational performance of early and midlactation cows.
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Optical Biosensor Based on Fluorescence Resonance Energy Transfer: Ultrasensitive and Specific Detection of Protein Toxins. J Am Chem Soc 1998. [DOI: 10.1021/ja981983r] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Optical Signal Transduction Triggered by Protein−Ligand Binding: Detection of Toxins Using Multivalent Binding. J Am Chem Soc 1998. [DOI: 10.1021/ja980246s] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Why Does D2 Bind Better Than H2? A Theoretical and Experimental Study of the Equilibrium Isotope Effect on H2 Binding in a M(η2-H2) Complex. Normal Coordinate Analysis of W(CO)3(PCy3)2(η2-H2). J Am Chem Soc 1997. [DOI: 10.1021/ja971009c] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Control of selected physical properties of MX solids: an experimental and theoretical investigation. J Mol Struct 1995. [DOI: 10.1016/0022-2860(95)08935-o] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Pressure tuning of the charge-density wave in the halogen-bridged transition-metal solid Pt2Br6(NH3)4. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:18682-18685. [PMID: 9976314 DOI: 10.1103/physrevb.50.18682] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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