107 results on '"Viswanathan V Krishnan"'
Search Results
102. Strong Coupling and Flip-Angle Dependence of Coupling Patterns in Heteronuclear Shift Correlation Two-Dimensional NMR Spectra
- Author
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Viswanathan V Krishnan, Anil Kumar, and Srinivasarao Raghothama
- Subjects
Coupling constant ,Coupling ,Chemistry ,Physics ,General Engineering ,Nuclear magnetic resonance spectroscopy ,Resonance (particle physics) ,Molecular physics ,NMR spectra database ,Nuclear magnetic resonance ,Heteronuclear molecule ,Molecule ,Multiplet ,Sophisticated Instruments Facility (Continued as NMR Research Centre) - Abstract
Heteronuclear shift correlation two-dimensional NMR spectroscopy (HETCOSY)(1-5) has become a powerful technique for resonance assignments of carbon and proton spectra, and for structural information of organic and biomolecules (6-10). Coupled HETCOSY has lower signal intensity than decoupled HETCOSY due to distribution of intensities into several peaks of each multiplet but gains in intensity by avoiding refocusing delays, the optimum of which depends on various parameters (1-5, II). The coupling patterns contain information which leads to unambiguous resonance assignments and signs of coupling constants (5). However, strong coupling effects associated with flip-angle variations can give rise to unusual multiplet patterns which require detailed analysis. The multiplet patterns in the HETCOSY experiments usually show characteristic patterns for various types of carbons in the molecule. On the other hand, the patterns arising from a methylene carbon, with two nonequivalent protons, which are often strongly coupled, change significantly with variations of the chemical shift of the protons and their couplings. In particular the intensities of the central peaks along the carbon axis show significant variations as a function of these parameters.
- Published
- 1988
103. Metric Scaling for Dimensionality Reduction of Disordered Protein Dynamics
- Author
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Shawn Newsam, Joshua L. Phillips, Michael Rexach, Viswanathan V Krishnan, Edmond Y. Lau, and Michael E. Colvin
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Folding (chemistry) ,chemistry.chemical_classification ,Molecular dynamics ,chemistry ,Globular protein ,Computational chemistry ,Protein dynamics ,Dimensionality reduction ,Protein domain ,Metric (mathematics) ,Biophysics ,Statistical physics ,Scaling - Abstract
One of the central tenets of molecular biology is the “protein structure-function” paradigm, which states that proteins adopt rigid 3-dimensional structures that are responsible for their function. There is now growing evidence that some proteins and protein domains exist as intrinsically disordered forms. Since traditional tools of biomolecular modeling focus on the fluctuation of the protein around a reference or canonical structure, new approaches are needed that do not use a single reference structure to define a metric for the dynamics of disordered biomolecules. Seemingly similar dynamics are observed for globular proteins during the folding process, so such techniques would also be beneficial to the study of non-equilibrium processes involving globular proteins. We show how classical metric scaling applied to molecular dynamics (MD) simulations of a class of entirely disordered proteins (outside of a small anchoring domain) involved in nucleocytoplasmic transport, the FG-nucleoporins (FG-nups), develops several key insights into the dynamics of the FG-nups, the adequacy of our simulation protocols, and also provides low-dimensional, detailed maps of the conformation space explored by the FG-nups. We then compare our results to those obtained from simulations of several unfolded globular proteins to see if the dynamics of folding proteins differ even at the earliest stages of the folding process.
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104. Gender Differences in Bile Acids and Microbiota in Relationship with Gender Dissimilarity in Steatosis Induced by Diet and FXR Inactivation
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Lili Sheng, Prasant Kumar Jena, Hui-Xin Liu, Karen M. Kalanetra, Frank J. Gonzalez, Samuel W. French, Viswanathan V. Krishnan, David A. Mills, and Yu-Jui Yvonne Wan
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Medicine ,Science - Abstract
Abstract This study aims to uncover how specific bacteria and bile acids (BAs) contribute to steatosis induced by diet and farnesoid X receptor (FXR) deficiency in both genders. A control diet (CD) and Western diet (WD), which contains high fat and carbohydrate, were used to feed wild type (WT) and FXR knockout (KO) mice followed by phenotyping characterization as well as BA and microbiota profiling. Our data revealed that male WD-fed FXR KO mice had the most severe steatosis and highest hepatic and serum lipids as well as insulin resistance among the eight studied groups. Gender differences in WD-induced steatosis, insulin sensitivity, and predicted microbiota functions were all FXR-dependent. FXR deficiency enriched Desulfovibrionaceae, Deferribacteraceae, and Helicobacteraceae, which were accompanied by increased hepatic taurine-conjugated cholic acid and β-muricholic acid as well as hepatic and serum lipids. Additionally, distinct microbiota profiles were found in WD-fed WT mice harboring simple steatosis and CD-fed FXR KO mice, in which the steatosis had a potential to develop into liver cancer. Together, the presented data revealed FXR-dependent concomitant relationships between gut microbiota, BAs, and metabolic diseases in both genders. Gender differences in BAs and microbiota may account for gender dissimilarity in metabolism and metabolic diseases.
- Published
- 2017
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105. The Ensemble of Conformations of Antifreeze Glycoproteins (AFGP8): A Study Using Nuclear Magnetic Resonance Spectroscopy
- Author
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Cheenou Her, Yin Yeh, and Viswanathan V. Krishnan
- Subjects
AFGP ,NMR ,ensemble of structures ,antifreeze proteins ,Microbiology ,QR1-502 - Abstract
The primary sequence of antifreeze glycoproteins (AFGPs) is highly degenerate, consisting of multiple repeats of the same tripeptide, Ala−Ala−Thr*, in which Thr* is a glycosylated threonine with the disaccharide beta-d-galactosyl-(1,3)-alpha-N-acetyl-d-galactosamine. AFGPs seem to function as intrinsically disordered proteins, presenting challenges in determining their native structure. In this work, a different approach was used to elucidate the three-dimensional structure of AFGP8 from the Arctic cod Boreogadus saida and the Antarctic notothenioid Trematomus borchgrevinki. Dimethyl sulfoxide (DMSO), a non-native solvent, was used to make AFGP8 less dynamic in solution. Interestingly, DMSO induced a non-native structure, which could be determined via nuclear magnetic resonance (NMR) spectroscopy. The overall three-dimensional structures of the two AFGP8s from two different natural sources were different from a random coil ensemble, but their “compactness” was very similar, as deduced from NMR measurements. In addition to their similar compactness, the conserved motifs, Ala−Thr*−Pro−Ala and Ala−Thr*−Ala−Ala, present in both AFGP8s, seemed to have very similar three-dimensional structures, leading to a refined definition of local structural motifs. These local structural motifs allowed AFGPs to be considered functioning as effectors, making a transition from disordered to ordered upon binding to the ice surface. In addition, AFGPs could act as dynamic linkers, whereby a short segment folds into a structural motif, while the rest of the AFGPs could still be disordered, thus simultaneously interacting with bulk water molecules and the ice surface, preventing ice crystal growth.
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- 2019
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106. Comprehensive Laboratory Evaluation of a Highly Specific Lateral Flow Assay for the Presumptive Identification of Bacillus anthracis Spores in Suspicious White Powders and Environmental Samples.
- Author
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Ramage JG, Prentice KW, DePalma L, Venkateswaran KS, Chivukula S, Chapman C, Bell M, Datta S, Singh A, Hoffmaster A, Sarwar J, Parameswaran N, Joshi M, Thirunavkkarasu N, Krishnan V, Morse S, Avila JR, Sharma S, Estacio PL, Stanker L, Hodge DR, and Pillai SP
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- Civil Defense methods, Immunoassay instrumentation, Powders, Reagent Strips, Reproducibility of Results, Sensitivity and Specificity, Bacillus anthracis isolation & purification, Bioterrorism prevention & control, Immunoassay methods, Spores, Bacterial isolation & purification
- Abstract
We conducted a comprehensive, multiphase laboratory evaluation of the Anthrax BioThreat Alert(®) test strip, a lateral flow immunoassay (LFA) for the rapid detection of Bacillus anthracis spores. The study, conducted at 2 sites, evaluated this assay for the detection of spores from the Ames and Sterne strains of B. anthracis, as well as those from an additional 22 strains. Phylogenetic near neighbors, environmental background organisms, white powders, and environmental samples were also tested. The Anthrax LFA demonstrated a limit of detection of about 10(6) spores/mL (ca. 1.5 × 10(5) spores/assay). In this study, overall sensitivity of the LFA was 99.3%, and the specificity was 98.6%. The results indicated that the specificity, sensitivity, limit of detection, dynamic range, and repeatability of the assay support its use in the field for the purpose of qualitatively evaluating suspicious white powders and environmental samples for the presumptive presence of B. anthracis spores.
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- 2016
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107. Role of receptors of advanced glycation end-products (RAGE) in type 2 diabetic and non-diabetic individuals with chronic periodontal disease: an immunohistochemical study.
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Rajeev K, Karthika R, Mythili R, Krishnan V, and Nirmal M
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- Age Factors, Biopsy methods, Dental Plaque Index, Diabetes Mellitus, Type 2 prevention & control, Endothelial Cells chemistry, Endothelium, Vascular chemistry, Epithelium chemistry, Humans, Immunohistochemistry, Periodontal Attachment Loss metabolism, Periodontal Index, Periodontal Pocket metabolism, Receptor for Advanced Glycation End Products, Chronic Periodontitis metabolism, Diabetes Mellitus, Type 2 metabolism, Gingiva chemistry, Receptors, Immunologic analysis
- Abstract
Aim: The relationship between diabetes and periodontal disease is well established. It has been shown that advanced glycation end-products might exert noxious effects on several tissues of the body through its receptor. Evidence for the role of receptors of advanced glycation end-products in periodontal disease for diabetes is limited, and their presence in human gingival tissues has been demonstrated in few studies. In this study, we demonstrate the presence of receptors of advanced glycation end-products in patients with chronic periodontitis, with and without type 2 diabetes., Methods: Gingival biopsies from 19 patients with both type 2 diabetes and chronic periodontitis, and 18 healthy controls with chronic periodontitis, were immunohistochemically stained for receptors of advanced glycation end-products., Results: On immunohistochemical analysis, positive staining for receptors of advanced glycation end-products was seen in the endothelium and the basal and spinous layers of the inflamed gingival epithelium in both type 2 diabetes and non-diabetes tissue, with a statistically-significant difference between both groups (P <0 .05)., Conclusions: There was a significant difference in receptors of advanced glycation end-product immune reactivity between both groups. Receptors of advanced glycation end-product increase in type 2 diabetes gingival tissue might indicate possible involvement of this receptor in periodontal destruction in individuals with type 2 diabetes., (© 2011 Blackwell Publishing Asia Pty Ltd.)
- Published
- 2011
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