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41.
Alcohol-induced conformational transitions of erv C, a highly stable cysteine protease, were followed by CD, fluorescence, and activity. At acidic pH, the addition of different alcohols caused two types of conformational transitions. Increasing the concentration of nonfluorinated alkyl alcohols induced a conformational switch from -helix to -sheet. Under these conditions, the protein lost its proteolytic activity and tertiary structure. The switch was a sudden one, observed in 50% methanol, 45% ethanol, and 40% propanol. Under similar conditions of pH and concentration, however, glycerol and TFE enhanced the -helicity of the protein. Methanol-induced denaturation was observed to occur in two stages; the first is the -sheet state stabilized at low alcohol concentrations, and the other is the -sheet state with enhanced ellipticity stabilized at high alcohol concentrations. This -sheet conformation can be attained from the native as well as 6 M GuHCl-denatured state by addition of methanol and exhibits properties different from the native or unfolded state. This state shows loss of tertiary structure and activity, enhanced nonnative secondary structure, noncooperative temperature unfolding, and higher stability toward denaturants as compared to the native state, which are characteristic of the molten globule-like state or O-state, and thus this state may be functioning as an intermediate in the folding pathway of erv C. 相似文献
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Cell property determination from the acoustic microscope generated voltage versus frequency curves 下载免费PDF全文
Among the methods for the determination of mechanical properties of living cells acoustic microscopy provides some extraordinary advantages. It is relatively fast, of excellent spatial resolution and of minimal invasiveness. Sound velocity is a measure of the stiffness or Young's modulus of the cell. Attenuation of cytoplasm is a measure of supramolecular interactions. These parameters are of crucial interest for studies of cell motility, volume regulations and to establish the functional role of the various elements of the cytoskeleton. Using a phase and amplitude sensitive modulation of a scanning acoustic microscope (Hillman et al., 1994, J. Alloys Compounds. 211/212:625-627) longitudinal wave speed, attenuation and thickness profile of a biological cell are obtained from the voltage versus frequency or V(f) curves. A series of pictures, for instance in the frequency range 980-1100 MHz with an increment of 20 MHz, allows the experimental generation of V(f) curves for each pixel while keeping the lens-specimen distance unchanged. Both amplitude and phase values of the V(f) curves are used for obtaining the cell properties and the cell thickness profile. The theoretical analysis shows that the thin liquid layer, between the cell and the substrate, has a strong influence on the reflection coefficient and should not be ignored during the analysis. Cell properties, cell profile and the thickness of the thin liquid layer are obtained from the V(f) curves by the simplex inversion algorithm. The main advantages of this new method are that imaging can be done near the focal plane, therefore an optimal signal to noise ratio is achieved, no interference with Rayleigh waves occurs, and the method requires only an approximate estimate of the material properties of the solid substratum where the cells are growing on. 相似文献
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Manalee Guha Biswabandhu Bankura Sudakshina Ghosh Arup Kumar Pattanayak Saurabh Ghosh Dilip Kumar Pal Anurag Puri Anup Kumar Kundu Madhusudan Das 《PloS one》2015,10(6)
Kidney stone disease (KSD) is a major clinical problem imposing a large burden for both healthcare and economy globally. In India, the prevalence of kidney stone disease is rapidly increasing. This study aimed to evaluate the association between genetic defects in vitamin D receptor (VDR), calcium sensing receptor (CaSR) and claudin 14 (CLDN14) genes and kidney stone disease in patients from eastern India. We enrolled 200 consecutive kidney stone patients (age 18–60 years) (cases) and their corresponding sex and age matched 200 normal individuals (controls). To identify genetic variants responsible for KSD, we performed sequence analysis of VDR, CaSR and CLDN14 genes. Four non-synonymous (rs1801725, rs1042636, rs1801726 and rs2228570), one synonymous (rs219780) and three intronic single nucleotide polymorphisms (SNPs) (rs731236, rs219777 and rs219778) were identified. Genotype and allele frequency analysis of these SNPs revealed that, rs1801725 (Ala986Ser), rs1042636 (Arg990Gly) of CaSR gene and rs219778, rs219780 (Thr229Thr) of CLDN14 gene were significantly associated with KSD. Serum calcium levels were significantly higher in subjects carrying 986Ser allele and calcium excretion was higher in subjects bearing 990Gly allele. In conclusion, rs1801725, rs1042636, rs219778 and rs219780 SNPs were associated with kidney stone risk in patients from the eastern part of India. 相似文献
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Duncan N. Ndegwa Prasun Kundu Jessica B. Hostetler Alejandro Marin-Menendez Theo Sanderson Kioko Mwikali Lisa H. Verzier Rachael Coyle Sophie Adjalley Julian C. Rayner 《PLoS pathogens》2021,17(7)
Plasmodium vivax is responsible for the majority of malaria cases outside Africa. Unlike P. falciparum, the P. vivax life-cycle includes a dormant liver stage, the hypnozoite, which can cause infection in the absence of mosquito transmission. An effective vaccine against P. vivax blood stages would limit symptoms and pathology from such recurrent infections, and therefore could play a critical role in the control of this species. Vaccine development in P. vivax, however, lags considerably behind P. falciparum, which has many identified targets with several having transitioned to Phase II testing. By contrast only one P. vivax blood-stage vaccine candidate based on the Duffy Binding Protein (PvDBP), has reached Phase Ia, in large part because the lack of a continuous in vitro culture system for P. vivax limits systematic screening of new candidates. We used the close phylogenetic relationship between P. vivax and P. knowlesi, for which an in vitro culture system in human erythrocytes exists, to test the scalability of systematic reverse vaccinology to identify and prioritise P. vivax blood-stage targets. A panel of P. vivax proteins predicted to function in erythrocyte invasion were expressed as full-length recombinant ectodomains in a mammalian expression system. Eight of these antigens were used to generate polyclonal antibodies, which were screened for their ability to recognize orthologous proteins in P. knowlesi. These antibodies were then tested for inhibition of growth and invasion of both wild type P. knowlesi and chimeric P. knowlesi lines modified using CRISPR/Cas9 to exchange P. knowlesi genes with their P. vivax orthologues. Candidates that induced antibodies that inhibited invasion to a similar level as PvDBP were identified, confirming the utility of P. knowlesi as a model for P. vivax vaccine development and prioritizing antigens for further follow up. 相似文献
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Jonojit Roy Soumi Naha Madhumita Majumdar Nirmalya Banerjee 《Plant Cell, Tissue and Organ Culture》2007,90(1):31-39
An efficient method of mass propagation of Dendrobium chrysotoxum Lindl. was developed using a shoot-tip culture system. Both direct and callus-mediated formation of protocorm-like bodies
(PLBs) occurred from the basal cut surface of explants. Frequency of callusing was best in the presence of 2 μM thidiazuron
(TDZ) or N6-benzylaminopurine (BAP). The callus exhibited complete hormone autonomy for growth and differentiation of PLBs and was maintained
for 18 months without any exogenous growth regulators, an aspect important for minimising somaclonal variation. However, the
rate of callus growth and PLB formation varied with application of cytokinin and auxin. In addition, the callus exhibited
a differential sensitivity to the exogenous cytokinins. While BAP promoted callus growth and PLB differentiation, TDZ was
inhibitory to callus mediated PLB formation and caused extensive necrosis of callus. Although α-naphthaleneacetic acid (NAA)
had no significant effect on the induction of callus, subsequent growth was best in its presence. Using a 3-month subculture
period, a 69-fold increase in callus weight was achieved with 0.5 μM NAA, while as many as 133 PLBs could be obtained per
100 mg callus in the presence of 1 μM NAA. For direct PLB formation, the optimum cytokinin dosage was dependent upon the type
of cytokinin used. While TDZ was most effective at a concentration of 1 μM (15 PLBs per explant), for similar PLB yield the
application of 8 μM BAP was essential. 相似文献
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Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) of pathogenic protozoa Trichomonas vaginalis (TvGAPDH) is an attractive drug target since this parasite lacks functional citric acid cycle and is dependent solely on glycolysis for its energy requirements. The three dimensional structure of TvGAPDH dimer has been generated by homology modelling based on the crystal structure of human liver GAPDH. Comparison of the NAD;{+} binding pocket of the modeled TvGAPDH with human GAPDH (hGAPDH) reveals the presence of a hydrophobic pocket near the N-6 position of adenine ring as well as a hydrophobic cleft near O-2' of the adenosine ribose that are absent in the human enzyme. In order to exploit these structural differences adenosine and several adenosine analogs with substitution on N-6 position of adenine ring or 2' position of ribose sugar or both have been studied by docking experiments using the program AutoDock version 3.0.5. Our docking result suggests that bulkier hydrophobic substitution at the N-6 position of the adenine ring could form more stable complexes with TvGAPDH than with hGAPDH. An improvement of binding occurs in TvGAPDH when methoxybenzamido group has been introduced at the O-2' position of the ribose sugar. The combination of N-6 and O-2' substitutions may have produced significantly improved inhibitors. Our study may help in identifying structural elements involved in the origin of selectivity at the NAD;{+} binding pocket of TvGAPDH. This study could further be extended for future anti-trichomonal drug design strategies in order to control trichomoniasis. 相似文献