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1.
Sherif Yehia C. Mitros Sanjeev Kumar S. Jha Glenn M. Julian R. A. Dunlap 《Hyperfine Interactions》1987,34(1-4):415-418
The systematics of hyperfine magnetic fields at sp impurities on the Z-sites in Co based Heusler alloys are investigated. New TDPAC measurements of Cd hyperfine fields are reported. 相似文献
2.
Kumar S Sharma D Ghosh G Kabir-ud-Din 《Langmuir : the ACS journal of surfaces and colloids》2005,21(21):9446-9450
Hydrophobic interactions control the morphologies of both surfactant aggregates and proteins. Globular proteins "denature" upon addition of excess amounts of denaturants such as urea. Understanding the microscopic basis of the urea effect on proteins or supramolecular aggregates such as micelles has always been a debated issue. Inspired by this need, the effect of urea (U), thiourea (TU), monomethylurea (MMU), dimethylurea(DMU), tetramethylurea (TMU), dimethylthiourea (DMTU), and tetramethylthiourea (TMTU) on the structural transition (spherical micelles to rod-shaped micelles, s --> r) in the sodium dodecylbenzenesulfonate (SDBS)-1-pentanol system has been investigated through dynamic light scattering(DLS) and viscosity measurements at 25 degrees C. 1-Pentanol, at 0.14 M, is found to promote s --> r in this system (0.2 M SDBS). The presence of the additives causes, in almost all cases, a decrease and increase in this 1-pentanol concentration depending upon the concentration and nature of the additive. These effects are explained in terms of an increased dielectric constant of the solvent medium due to the presence of additives and increased micellar hydration due to the repulsion of charged monomers caused by adsorption of the additives. Taken together, the data signal the exposure of biological assemblies to water at higher [additive], which causes a decrease in hydrophobic interactions responsible for compact structure formation (i.e., native protein). 相似文献
3.
Samuel K Yin W Stearns RA Tang YS Chaudhary AG Jewell JP Lanza T Lin LS Hagmann WK Evans DC Kumar S 《Journal of mass spectrometry : JMS》2003,38(2):211-221
Metabolic activation of drug candidates to electrophilic reactive metabolites that can covalently modify cellular macromolecules may result in acute and/or idiosyncratic immune system-mediated toxicities in humans. This presents a significant potential liability for the future development of these compounds as safe therapeutic agents. We present here an example of an approach where sites of metabolic activation within a new drug candidate series were rapidly identified using online liquid chromatography/multi-stage mass spectrometry on an ion trap mass spectrometer. This was accomplished by trapping the reactive intermediates formed upon incubation of compounds with rat and human liver microsomes as their corresponding glutathione conjugates and mass spectral characterization of these thiol adducts. Based on the structures of the GSH adducts identified, potential sites and mechanisms of bioactivation within the chemical structure were proposed. These metabolism studies were interfaced with iterative structural modifications of the chemical series in order to block these bioactivation sites within the molecule. This strategy led to a significant reduction in the propensity of the compounds to undergo metabolic activation as evidenced by reductions in the irreversible binding of radioactivity to liver microsomal material upon incubation of tritium-labeled compounds with this in vitro system. With the efficiency and throughput achievable with such an approach, it appears feasible to identify and address the metabolic activation potential of new drug leads during routine metabolite identification studies in an early drug discovery setting. 相似文献
4.
Herein we describe a strategy for the preparation of artificial alpha-helices involving replacement of one of the main-chain hydrogen bonds with a covalent linkage. To mimic the C=O...H-N hydrogen bond as closely as possible, we envisioned a covalent bond of the type C=X-Y-N, where X and Y are two carbon atoms connected through an olefin metathesis reaction. Our results demonstrate that the replacement of a hydrogen bond between the i and i + 4 residues at the N-terminus of a short peptide with a carbon-carbon bond results in a highly stable constrained alpha-helix at physiological conditions as indicated by CD and NMR spectroscopies. The advantage of this strategy is that it allows access to short alpha-helices with strict preservation of molecular recognition surfaces required for biomolecular interactions. 相似文献
5.
JPC – Journal of Planar Chromatography – Modern TLC - A water-in-oil microemulsion has been used for the first time as a mobile phase in thin-layer chromatography of amino acids. A new... 相似文献
6.
Reactions of biscyclopentadienyl (and bisindenyl) titanium (IV) dichlorides with sodium salts of various thiocarboxylic acids in tetrahydrofuran medium, yield the complexes of the general formula (D) 2Ti(SCOR) 2 where D is cyclopentadienyl or indenyl group and R? H, CH3, C2H5, C4H5 or p-C4H4CH3 group. The foul smelling complexes are monomeric in nature. The IR spectra, thermal stabilities and Some physical characteristics of these complexes have been studied. 相似文献
7.
Sanjeev K. Garg 《Tetrahedron letters》2005,46(10):1721-1724
Copper(II) tetrafluoroborate has been found to be a new and highly efficient catalyst for Michael addition of thiols to α,β-unsaturated carbonyl compounds under solvent-free conditions and in H2O at room temperature. The reactions are very fast and are completed in 2 min to 1 h affording high yields. The rate of thiol addition was dependent on the steric hindrance at the β-carbon of the α,β-unsaturated carbonyl substrate. In the case of chalcones, the reactions are best carried out in MeOH as solvent. 相似文献
8.
The Ramanujan Journal - This paper provides elementary proofs for several types of congruences involving multipartitions and self-convolutions of the divisor function. Our computations use... 相似文献
9.
10.
We study the effect of hard-core repulsion (known as the bus effect) betweenB particles on the reaction-diffusion systemA+BB in the continuous-time random walk model in one dimension with theA particles stationary. We show rigorously that the survival probability of theA particles is asymptotically bounded asC
1lim
t{[–logS(t)]/t
0.5}C
2, whereC
1 andC
2 are constants. We also do simulations to confirm our results. 相似文献