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  • Author: P. R. Krishna x
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Abstract

An analysis of neutron diffraction data of liquid deuterated terr-butanol at room temperature to determine its molecular conformation is presented. Being a big molecule of 15 sites, the analysis is tricky and needs careful consideration. The resulting molecular parameters are compared with those obtained from other experimental data analysis and model calculations. The information about the intermolecular structural correlations, hydrogen-bonded molecular association in particular is also obtained from the diffraction data analysis. -PACS number: 61.25

Summary

Ion exchange properties of cesium, strontium and europium on uranium antimonate (USb) from nitric acid medium was studied. The distribution coefficient (K d) of 1046 mL/g for cesium, 2464 mL/g for strontium and ∼105 mL/g for europium were obtained for sorption from 0.01 M nitric acid and K d decreased with increase in the concentration of nitric acid. Rapid sorption of metal ions in the initial stages of equilibration followed by the establishment of equilibrium after 24 hours. Cesium sorption on USb follows ideal ion exchange while strontium and europium do not. From Langmuir adsorption model for the sorption of these ions on USb, the apparent sorption capacity was found to be of 6.9 mg/g for cesium, 19.1 mg/g for strontium and 37.2 mg/g for europium at 300 K. The enthalpy change (ΔH°) accompanied by the sorption was determined by the temperature variation method. The performance of the sorbent under dynamic conditions was assessed by following a breakthrough (BT) curve up to C/C 0=1. Extraction chromatography of individual ions from the mixture using USb was also reported in this paper.

Abstract

The dehydration mechanism of natural single crystals of gypsum was investigated in the temperature range 300-430 K by in situ infrared (FTIR) spectroscopy. The thermal evolution of the second-order modes of H2O and SO4 groups in gypsum, in the wavenumber range 4850.5450 cm-1 and 2050.2300 cm-1 respectively, were used to probe the dehydration and rehydration sequence. A total disappearance of the combination modes of H2O and the replacement of four SO-2 4 bands (2245, 2200, 2133, and 2117 cm-1) observed at room temperature by three bands (2236, 2163, and 2131 cm-1) observed at 390 K indicates the direct formation of γ-CaSO4 upon heating. Upon cooling water re-enters into the γ-CaSO4 structure at around 363 K to form bassanite. This observation, that the dehydration of gypsum directly yields γ-CaSO4 (anhydrite) without the intermediate formation of hemi-hydrate (bassanite), is further corroborated by the dehydration behavior of bassanite. The second-order SO4 modes of bassanite observed around 2218, 2136, and 2096 cm-1 were replaced with the bands of γ-CaSO4 at about 378 K upon heating.

Abstract

Background: The efficacy of opioids in neuropathic pain is still controversial. Earlier studies have suggested that N-methyl-D-aspartate (NMDA) receptor binding can be affected by opioids and vice versa. The present study aims to explore the interactions between NMDA and opioid receptors using various combinations of drugs acting on these receptors.

Methods: We used an animal model of sciatic nerve ligation to induce neuropathic pain, and a hot-plate test was used to assess pain response.

Results: It was observed that NMDA and naloxone increased the pain response. Ketamine reduced the pain response, which was further reduced when ketamine was administered in combination with naloxone, but not with NMDA, thus highlighting the activity of the NMDA receptor system. In addition, morphine was also found to increase latency to hind-paw lick, which was further reduced when given in combination with naloxone. Furthermore, triple drug combinations using ketamine+morphine+naloxone and ketamine+NMDA+naloxone demonstrated some significant interactions at these receptors.

Conclusions: Thus, our study establishes that neuropathic pain can probably be overcome using higher doses of opioids, and there exists some intimate relationships between NMDA and opioid systems that lead to pain modulation.

Abstract

Rickettsial species have independently lost several genes owing to reductive evolution while retaining those predominantly implicated in virulence, survival, and biosynthetic pathways. In this study, we have identified a previously uncharacterized Rickettsia conorii gene RC0497 as an N-acetylmuramoyl-L-alanine amidase constitutively expressed during infection of cultured human microvascular endothelial cells at the levels of both mRNA transcript and encoded protein. A homology-based search of rickettsial genomes reveals that RC0497 homologs, containing amidase_2 family and peptidoglycan binding domains, are highly conserved among the spotted fever group (SFG) rickettsiae. The recombinant RC0497 protein exhibits α-helix secondary structure, undergoes a conformational change in the presence of zinc, and exists as a dimer at higher concentrations. We have further ascertained the enzymatic activity of RC0497 via demonstration of its ability to hydrolyze Escherichia coli peptidoglycan. Confocal microscopy on E. coli expressing RC0497 and transmission immunoelectron microscopy of R. conorii revealed its localization predominantly to the cell wall, septal regions of replicating bacteria, and the membrane of vesicles pinching off the cell wall. In summary, we have identified and functionally characterized RC0497 as a peptidoglycan hydrolase unique to spotted fever rickettsiae, which may potentially serve as a novel moonlighting protein capable of performing multiple functions during host-pathogen interactions.