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41.
K.K. Sarker S. Saha Halder T.K. Mondal P.K. Nanda C. Sinha 《Inorganica chimica acta》2010,363(12):2955-623
Reaction of Cu(ClO4)2·6H2O, SRaaiNR′ (1-alkyl-2-[(o-thioalkyl)phenylazo]imidazole) and NH4SCN (1:1:2 mol ratio) affords distorted square pyramidal, [CuII(SRaaiNR′)(SCN)2] (3) compound while identical reaction with [Cu(MeCN)4](ClO4) yields -SCN- bridged coordination polymer, [CuI(SRaaiNR′)(SCN)]n (4). These two redox states [CuII and CuI] are interconvertible; reduction of [CuII(SRaaiNR′)(SCN)2] by ascorbic acid yields [CuI(SRaaiNR′)(SCN)]n while the oxidation of [CuI(SRaaiNR′)(SCN)]n by H2O2 in presence of excess NH4SCN affords [CuII(SRaaiNR′)(SCN)2]. They are structurally confirmed by single crystal X-ray diffraction study. Cyclic voltammogram of the complexes show Cu(II)/Cu(I) redox couple at ∼0.4 V and azo reductions at negative to SCE. UV light irradiation in MeCN solution of [CuI(SRaaiNR′)(SCN)]n (4) show trans-to-cis isomerisation of coordinated azoimidazole. The reverse transformation, cis-to-trans, is very slow with visible light irradiation while the process is thermally accessible. Quantum yields (?t→c) of trans-to-cis isomerisation are calculated and free ligands show higher ? than their Cu(I) complexes. The activation energy (Ea) of cis-to-trans isomerisation is calculated by controlled temperature experiment. Copper(II) complexes, 3, do not show photochromism. DFT and TDDFT calculation of representative complexes have been used to determine the composition and energy of molecular levels and results have been used to explain the solution spectra, photochromism and redox properties of the complexes. 相似文献
42.
Jianping P. Wang Suleiman S. Bughrara Rouf M. A. Mian Malay C. Saha David A. Sleper 《Molecular breeding : new strategies in plant improvement》2009,23(2):299-309
Intergeneric hybridization between Festuca and Lolium has been a long-term goal of forage and turfgrass breeders to generate improved cultivars by combining stress tolerance of
Festuca and rapid establishment of Lolium. However, wide-distance hybridizations usually result in the wild genome being eliminated from the hybrid due to incomplete
chromosome pairing and crossovers. In this study, random amplified polymorphic DNA (RAPD) and simple sequence repeat (SSR)
markers were used to detect the parental genome composition of F1 hybrids and backcross, generated from crosses between Festuca mairei St. Yves (Fm) and Lolium perenne L. (Lp). Each of the hybrids exhibited integration of Fm and Lp genomes with varying levels of Fm/Lp genome ratios. However,
cluster and principle component analyses of the progeny consistently revealed four groups depending on the amount of genome
introgression from both parents. The parental genome composition and classifications of intergeneric progeny would be useful
for breeding material selection.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
43.
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45.
Debajit Saha David Morton Michael Ariel Ralf Wessel 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2011,197(2):153-165
The optic tectum holds a central position in the tectofugal pathway of non-mammalian species and is reciprocally connected
with the nucleus isthmi. Here, we recorded from individual nucleus isthmi pars parvocellularis (Ipc) neurons in the turtle
eye-attached whole-brain preparation in response to a range of computer-generated visual stimuli. Ipc neurons responded to
a variety of moving or flashing stimuli as long as those stimuli were small. When mapped with a moving spot, the excitatory
receptive field was of circular Gaussian shape with an average half-width of less than 3°. We found no evidence for directional
sensitivity. For moving spots of varying sizes, the measured Ipc response-size profile was reproduced by the linear Difference-of-Gaussian
model, which is consistent with the superposition of a narrow excitatory center and an inhibitory surround. Intracellular
Ipc recordings revealed a strong inhibitory connection from the nucleus isthmi pars magnocellularis (Imc), which has the anatomical
feature to provide a broad inhibitory projection. The recorded Ipc response properties, together with the modulatory role
of the Ipc in tectal visual processing, suggest that the columns of Ipc axon terminals in turtle optic tectum bias tectal
visual responses to small dark changing features in visual scenes. 相似文献
46.
Sisir Ghosh Pallab Ghosh Pradipta Saha Tushar Kanti Maiti 《Symbiosis (Philadelphia, Pa.)》2011,53(2):75-81
The symbiont isolated from root nodules of Phaseolus mungo L., a widely grown legume in India was identified as a Rhizobium sp. a Rhizobium sp. close to R. multihospitium based on a biochemical and 16S rRNA gene-based phylogenetic approach. This Rhizobium sp. was able to produce large amounts of extracellular polysaccharides (EPS) in a yeast extract mannitol (YEM) broth medium.
Both growth and EPS production started simultaneously though each had different stationary phases. EPS production increased
enormously with supplementation by the preferred carbon, nitrogen and vitamin sources. Attempts were made to optimize the
cultural requirements for maximum growth and maximum EPS production. The EPS produced by the symbiont contained large amount
of mannose together with small amounts of arabinose and xylose. The possible role of EPS production on the Rhizobium—root nodule symbiosis is briefly discussed. 相似文献
47.
Wang Y Keck ZY Saha A Xia J Conrad F Lou J Eckart M Marks JD Foung SK 《The Journal of biological chemistry》2011,286(51):44218-44233
A potent neutralizing antibody to a conserved hepatitis C virus (HCV) epitope might overcome its extreme variability, allowing immunotherapy. The human monoclonal antibody HC-1 recognizes a conformational epitope on the HCV E2 glycoprotein. Previous studies showed that HC-1 neutralizes most HCV genotypes but has modest potency. To improve neutralization, we affinity-matured HC-1 by constructing a library of yeast-displayed HC-1 single chain Fv (scFv) mutants, using for selection an E2 antigen from one of the poorly neutralized HCVpp. We developed an approach by parallel mutagenesis of the heavy chain variable (VH) and κ-chain variable (Vk) genes separately, then combining the optimized VH and Vk mutants. This resulted in the generation of HC-1-related scFv variants exhibiting improved affinities. The best scFv variant had a 92-fold improved affinity. After conversion to IgG1, some of the antibodies exhibited a 30-fold improvement in neutralization activity. Both surface plasmon resonance and solution kinetic exclusion analysis showed that the increase in affinity was largely due to a lowering of the dissociation rate constant, Koff. Neutralization against a panel of HCV pseudoparticles and infectious 2a HCV virus improved with the affinity-matured IgG1 antibodies. Interestingly, some of these antibodies neutralized a viral isolate that was not neutralized by wild-type HC-1. Moreover, propagating 2a HCVcc under the selective pressure of WT HC-1 or affinity-matured HC-1 antibodies yielded no viral escape mutants and, with the affinity-matured IgG1, needed 100-fold less antibody to achieve complete virus elimination. Taken together, these findings suggest that affinity-matured HC-1 antibodies are excellent candidates for therapeutic development. 相似文献
48.
A population genetic study was undertaken to investigate the origin of Koreans. Thirteen polymorphic and 7 monomorphic blood genetic markers (serum proteins and red cell enzymes) were studied in a group of 437 Koreans. Genetic distance analyses by both cluster and principal components models were performed between Koreans and eight other populations (Koreans in China, Japanese, Han Chinese, Mongolians, Zhuangs, Malays, Javanese, and Soviet Asians) on the basis of 47 alleles controlled by 15 polymorphic loci. A more detailed analysis using 65 alleles at 19 polymorphic loci was performed on six populations. Both analyses demonstrated genetic evidence of the origin of Koreans from the central Asian Mongolians. Further, the Koreans are more closely related to the Japanese and quite distant from the Chinese. The above evidence of the origin of Koreans fits well with the ethnohistoric account of the origin of Koreans and the Korean language. The minority Koreans in China also maintained their genetic identity. 相似文献
49.
Chowdhury F Rahman MA Begum YA Khan AI Faruque AS Saha NC Baby NI Malek MA Kumar AR Svennerholm AM Pietroni M Cravioto A Qadri F 《PLoS neglected tropical diseases》2011,5(4):e999
Background
In Bangladesh, increases in cholera epidemics are being documented with a greater incidence and severity. The aim of this prospective study was to identify the prevalence and importance of V. cholerae O1 and enterotoxigenic Escherichia coli (ETEC) as causal agents of severe diarrhea in a high diarrhea prone urban area in Dhaka city.Methodology
Systematic surveillance was carried out on all diarrheal patients admitted from Mirpur between March 2008 to February 2010 at the ICDDR, B hospital. Stool or rectal swabs were collected from every third diarrheal patient for microbiological evaluation.Principal Findings
Of diarrheal patients attending the hospital from Mirpur, 41% suffered from severe dehydration with 39% requiring intravenous rehydration therapy. More diarrheal patients were above five years of age (64%) than those below five years of age (36%). About 60% of the patients above five years of age had severe dehydration compared with only 9% of patients under five years of age. The most prevalent pathogen isolated was Vibrio cholerae O1 (23%) followed by ETEC (11%). About 8% of cholera infection was seen in infants with the youngest children being one month of age while in the case of ETEC the rate was 11%. Of the isolated ETEC strains, the enterotoxin type were almost equally distributed; ST accounted for 31% of strains; LT/ST for 38% and LT for 31%.Conclusion
V. cholerae O1 is the major bacterial pathogen and a cause of severe cholera disease in 23% of patients from Mirpur. This represents a socioeconomic group that best reflects the major areas of high cholera burden in the country. Vaccines that can target such high risk groups in the country and the region will hopefully be able to reduce the disease morbidity and the transmission of pathogens that impact the life and health of people. 相似文献50.