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301.
Ali E. I. Elkhalifah M. Azmi Bustam T. Murugesan 《Journal of Thermal Analysis and Calorimetry》2013,112(2):929-935
In the present study, different transition metal forms of montmorillonite have been intercalated with mono-, di-, and triethanolammonium cations via d coordination mechanism to investigate their thermal behavior, structural characteristics, surface properties, and elemental composition using TG, XRD, BET, and CHNS techniques. Thermogravimetric analysis showed two thermal transition steps for transition metal-exchanged montmorillonites, which attributed to desorption of the physically adsorbed water and hydrated water, and dehydroxylation of the structural water; whereas for ammonium-montmorillonite complexes, the TG curves showed three thermal transition steps which attributed to desorption of the adsorbed water and dehydration, decomposition of the ammonium cations in the interlayer space of montmorillonite, and the dehydroxylation of the structural water. The thermal analysis of ammonium-montmorillonites affirmed that the molar mass of amine compounds used affects both desorption temperature (position) and the amount of the adsorbed water (intensity). XRD results revealed that the molar mass of amine used has linear relation with the basal spacings of the corresponding ammonium-montmorillonites, indicating structural changes. BET results showed that the molar mass of amines has an inverse effect on the surface area of the studied samples. CHNS analysis for the studied samples quantitatively confirmed the intercalation of ammonium cations into the interlayer space of montmorillonite. 相似文献
302.
Yesuthangam Y Pandian S Venkatesan K Gandhidasan R Murugesan R 《Journal of photochemistry and photobiology. B, Biology》2011,102(3):200-208
This paper describes the synthesis and photodynamic properties of six different chalcone derivatives. Using N,N-dimethyl-4-nitrosoaniline (RNO) bleaching assay, the singlet oxygen generating efficiencies of these chalcones are determined relative to rose bengal (RB). Superoxide dismutase (SOD) inhibitable cytochrome c reduction assay and electron magnetic resonance (EMR) spin trapping techniques are used to determine the superoxide anion radical (O?·?) yield upon photoirradiation. Photoinduced DNA scission studies show that O?·? is involved in the DNA strand break. In addition, antimicrobial activity of these chalcones is also investigated. Structure activity relationship accounts for the difference in the photogeneration of reactive oxygen species (ROS) by these sensitizers. Presence of electron releasing -OCH? groups enhances the photogeneration of ROS. Cyclic voltammetry studies indicate a correlation between enzymatic O?·? generation efficiency and redox potential of chalcones. Both O?·? (Type I) and 1O? (Type II) paths are involved in the photosensitization of chalcones. The LUMO energies obtained by molecular modeling correlate with the one-electron reduction potentials. 相似文献
303.
Kan ZY Mayne L Chetty PS Englander SW 《Journal of the American Society for Mass Spectrometry》2011,22(11):1906-1915
A previous paper considered the problems that presently limit the hydrogen exchange - mass spectrometry (HX-MS) method for
studying the biophysical and functional properties of proteins. Many of these problems can be overcome by obtaining and analyzing
hundreds of sequentially overlapping peptide fragments that cover the protein many times over (Mayne et al. J. Am. Soc. Mass
Spectrom. 2011: ). This paper describes a computer program called ExMS that furthers this advance by making it possible to efficiently process
crowded mass spectra and definitively identify and characterize these many peptide fragments. ExMS automatically scans through
high resolution MS data to find the individual isotopic peaks and isotopic envelopes of a list of peptides previously identified
by MS/MS. It performs a number of tests to ensure correct identification in spite of peptide overlap in both chromatographic
and mass spectrometric dimensions and possible multi-modal envelopes due to static or dynamic structural heterogeneity or
HX EX1 behavior. The program can automatically process data from many sequential HX time points with no operator intervention
at the rate of ~2 sec per peptide per HX time point using desktop computer equipment, but it also provides for rapid manual
checking and decision when ambiguity exists. Additional subroutines can provide a step by step report of performance at each
test along the way and parameter adjustment, deconvolute isotopic envelopes, and plot the time course of single and multi-modal
H-D exchange. The program will be available on an open source basis at: 相似文献
304.
Mayne L Kan ZY Chetty PS Ricciuti A Walters BT Englander SW 《Journal of the American Society for Mass Spectrometry》2011,22(11):1898-1905
Measurement of the naturally occurring hydrogen exchange (HX) behavior of proteins can in principle provide highly resolved
thermodynamic and kinetic information on protein structure, dynamics, and interactions. The HX fragment separation-mass spectrometry
method (HX-MS) is able to measure hydrogen exchange in biologically important protein systems that are not accessible to NMR
methods. In order to achieve high structural resolution in HX-MS experiments, it will be necessary to obtain many sequentially
overlapping peptide fragments and be able to identify and analyze them efficiently and accurately by mass spectrometry. This
paper describes operations which, when applied to four different proteins ranging in size from 140 to 908 residues, routinely
provides hundreds of useful unique peptides, covering the entire protein length many times over. Coverage in terms of the
average number of peptide fragments that span each amino acid exceeds 10. The ability to achieve these results required the
integrated application of experimental methods that are described here and a computer analysis program, called ExMS, described
in a following paper. 相似文献
305.
In the present work, an attempt has been made to assess the bioconcentration and distribution of zinc on the selected organs of Labeo rohita and to study the effect of zinc exposure on the biochemical constitutions of gill tissues of L. rohita by using FT-IR Spectroscopy. The concentration pattern in the organs reveals that the liver is the prime site of metal binding and muscle accumulates least metal concentration. The accumulation profile is in the order: liver > gill > kidney > brain > bone > muscle. It has also been observed that the administration of chelating agent d-Penicillamine (DPA) reduces the zinc concentration in all tissues more effectively than the administration of the chelating agent Ethylene Diamine Tetra Acetic acid. The FT-IR spectra reveal that zinc exposure causes significant changes in the biochemical constitutions of the gill tissues. It causes an alteration in the protein secondary structures by decreasing the α-helix and increasing the β-sheet contents. Further, it has been observed that the administration of chelating agent DPA improves the protein and lipid contents in the gill tissues compared to zinc exposed tissues. This result shows that DPA is the effective chelator of zinc in reducing the body burden of L. rohita fingerlings. In conclusion, the findings of the current study suggest that zinc exposure causes significant changes in both lipids and proteins of the gill tissues, and changes the protein profile in favour of β-sheet structure. 相似文献
306.
Dr. Laidong Zhou Dr. J. David Bazak Dr. Baltej Singh Chang Li Dr. Abdeljalil Assoud Dr. Nancy M. Washton Dr. Vijayakumar Murugesan Prof. Linda F. Nazar 《Angewandte Chemie (International ed. in English)》2023,62(30):e202300404
We report a new sodium fast-ion conductor, Na3B5S9, that exhibits a high Na ion total conductivity of 0.80 mS cm−1 (sintered pellet; cold-pressed pellet=0.21 mS cm−1). The structure consists of corner-sharing B10S20 supertetrahedral clusters, which create a framework that supports 3D Na ion diffusion channels. The Na ions are well-distributed in the channels and form a disordered sublattice spanning five Na crystallographic sites. The combination of structural elucidation via single crystal X-ray diffraction and powder synchrotron X-ray diffraction at variable temperatures, solid-state nuclear magnetic resonance spectra and ab initio molecular dynamics simulations reveal high Na-ion mobility (predicted conductivity: 0.96 mS cm−1) and the nature of the 3D diffusion pathways. Notably, the Na ion sublattice orders at low temperatures, resulting in isolated Na polyhedra and thus much lower ionic conductivity. This highlights the importance of a disordered Na ion sublattice—and existence of well-connected Na ion migration pathways formed via face-sharing polyhedra—in dictating Na ion diffusion. 相似文献