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91.
Experiments in which phospholipase A2 has been used to examine the accessibility of phospholipids on the surface of sickled erythrocytes and of spectrin-free spicules derived from these cells have shown that accessibility is essentially unchanged compared with oxygenated sickle or normal erythrocytes. These results conflict with the claims of other workers that sickling is accompanied by loss of lipid asymmetry and that spectrin is important in maintaining the normal distribution of phospholipids in the erythrocyte membrane.  相似文献   
92.
Zinebi  S.  Raval  G.  Petitdemange  H. 《Current microbiology》1994,29(2):79-85
Klebsiella oxytoca ZS fermented glucose to ethanol and lactic, formic, and acetic acids, but, in contrast to many strains, accumulates pyruvic and acetic acids as the principal end products in aerobic growth conditions. This strain was grown in sulfate-limited chemostat at a fixed low dilution rate (D=0.033 h–1) with glucose present in excess. When oxygen was supplied at a high level, pyruvate and acetate were produced, and the ratio NADH/NAD+ was low (0.04) while the internal pyruvate concentration increased to 100 mol (g dry wt)–1. A shortage of oxygen supply was accompanied by lactate production, an increase of the ratio NADH/NAD+ (0.53), and an undetectable level in internal pyruvate concentration. The observed changes in LDH activity found in vitro in extracts of the cells are not strictly related to those found in vivo. In fact, the specific activity of LDH was essentially stable at 30% of dissolved oxygen tension (d.o.t.) and decreased slightly at 60% of d.o.t., whereas specific lactic acid production decreased rapidly. The in vitro LDH activity was strongly affected by the NADH/NAD+ ratio.  相似文献   
93.
Various metabolites were analyzed in groundnut genotypes grown under varying temperature regimes (based on date of sowing). Four contrasting groundnut genotypes viz. ICGS44 (high-temperature tolerant), AK159 and GG7 (moderately-high-temperature tolerant), and DRG1 (high-temperature sensitive) were grown at three different temperature regimes i.e., low (early date of sowing), normal (normal date of sowing) and high temperature (late date of sowing) under field conditions. Untargeted metabolomic analysis of leaf tissue was performed by GC–MS, while targeted metabolite profiling was carried out by HPLC (polyamines) and UPLC-MS/MS (phenolics) at both the pegging and pod filling stages. Untargeted metabolomic profiling revealed exclusive expression/induction of beta-d-galactofuranoside, l-threonine, hexopyranose, d-glucopyranose, stearic acid, 4-ketoglucose, d-gulose, 2-o-glycerol-alpha-d-galactopyranoside and serine in ICGS44 during the pegging stage under high-temperature conditions. During the pod filling stage at higher temperature, alpha-d-galactoside, dodecanedioic acid, 1-nonadecene, 1-tetradecene and beta-d-galactofuranose were found to be higher in both ICGS44 and GG7. Moreover, almost all the metabolites detected by GC–MS were found to be higher in GG7, except beta-d-galactopyranoside, beta-d-glucopyranose, inositol and palmitic acid. Accumulation of putrescine was observed to be higher during low-temperature stress, while agmatine showed constitutive expression in all the genotypes, irrespective of temperature regime and crop growth stage. Interestingly, spermidine was observed only in the high-temperature tolerant genotype ICGS44. In our study, we found a higher accumulation of cinnamic acid, caffeic acid, salicylic acid and vanillic acid in ICGS44 compared to that of other genotypes at the pegging stage, whereas catechin and epicatechin were found during the pod filling stage in response to high-temperature stress, suggesting their probable roles in heat-stress tolerance in groundnut.  相似文献   
94.
A three-dimensional model of the PsbS protein was built with the help of homology-modeling methods. This protein is also known as CP22 and is associated with the protection of photosystem II of thylakoid from excess quanta of light energy absorbed by the photosynthetic apparatus. PsbS is reported to bind two molecules of zeaxanthin at low pH (<5.0) and is believed to be essential for rapid nonphotochemical quenching (qE) of chlorophyll a fluorescence in photosystem II. An attempt was made to explain the pH modulation of the conformation of protein through salt-bridges Glu(122)-Lys+(113) and Glu(226)-Lys+(217). Binding of two molecules of zeaxanthin in the three-dimensional model of PsbS is postulated. The molecular mechanism of photoprotection by PsbS is explained through the model. 1 Backbone structure of the PsbS protein with two molecules of all trans zeaxanthin (ZEX). Residues Glu 90, 122, 194, 226 and Lys 113, 217 are shown. The figure is drawn with RASMOL (Molecular Visualization Program, RasMol V2.6, Roger Sayle, Glaxo Wellcome Research and Development, Stevenage, Hertfordshire, UK) Electronic Supplementary Material Supplementary material is available for this article at  相似文献   
95.
DNA methylation is the best-studied epigenetic modification and describes the conversion of cytosine to 5-methylcytosine. The importance of this phenomenon is that aberrant promoter hypermethylation is a common occurrence in cancer and is frequently associated with gene silencing. Various techniques are currently available for the analysis of DNA methylation. However, accurate and reproducible quantification of DNA methylation remains challenging. In this report, we describe Bio-COBRA (combined bisulfite restriction analysis coupled with the Agilent 2100 Bioanalyzer platform), as a novel approach to quantitative DNA methylation analysis. The combination of a well-established method, COBRA, which interrogates DNA methylation via the restriction enzyme analysis of PCR-amplified bisulfite treated DNAs, with the Bioanalyzer platform allows for the rapid and quantitative assessment of DNA methylation patterns in large sample sets. The sensitivity and reproducibility of Bio-COBRA make it a valuable tool for the analysis of DNA methylation in clinical samples, which could aid in the development of diagnostic and prognostic parameters with respect to disease detection and management.  相似文献   
96.
MOTIVATION: The Bayesian network approach is a framework which combines graphical representation and probability theory, which includes, as a special case, hidden Markov models. Hidden Markov models trained on amino acid sequence or secondary structure data alone have been shown to have potential for addressing the problem of protein fold and superfamily classification. RESULTS: This paper describes a novel implementation of a Bayesian network which simultaneously learns amino acid sequence, secondary structure and residue accessibility for proteins of known three-dimensional structure. An awareness of the errors inherent in predicted secondary structure may be incorporated into the model by means of a confusion matrix. Training and validation data have been derived for a number of protein superfamilies from the Structural Classification of Proteins (SCOP) database. Cross validation results using posterior probability classification demonstrate that the Bayesian network performs better in classifying proteins of known structural superfamily than a hidden Markov model trained on amino acid sequences alone.  相似文献   
97.
The heritability of B cell chronic lymphocytic leukemia (CLL) is relatively high; however, no predisposing mutation has been convincingly identified. We show that loss or reduced expression of death-associated protein kinase 1 (DAPK1) underlies cases of heritable predisposition to CLL and the majority of sporadic CLL. Epigenetic silencing of DAPK1 by promoter methylation occurs in almost all sporadic CLL cases. Furthermore, we defined a disease haplotype, which segregates with the CLL phenotype in a large family. DAPK1 expression of the CLL allele is downregulated by 75% in germline cells due to increased HOXB7 binding. In the blood cells from affected family members, promoter methylation results in additional loss of DAPK1 expression. Thus, reduced expression of DAPK1 can result from germline predisposition, as well as epigenetic or somatic events causing or contributing to the CLL phenotype.  相似文献   
98.
Intra-arterial (IA) delivery of mesenchymal stem cells (MSCs) for acute ischemic stroke is attractive for clinical translation. However, studies using rat model of stroke have demonstrated that IA MSCs delivery can decrease middle cerebral artery (MCA) flow, which may limit its clinical translation. The goal of this study is to identify a dose of IA MSCs (maximum tolerated dose; MTD) that does not compromise MCA flow and evaluate its efficacy and optimal timing in a rat model of reversible middle cerebral artery occlusion (rMCAo). We sought to determine if there is a difference in efficacy of acute (1 h) versus sub-acute (24 h) IA MSCs treatment after rMCAo. Adult female Sprague-Dawley rats underwent rMCAo (90 min) and an hour later a single dose of MSCs (at de-escalating doses 1×106, 5×105, 2×105, 1×105 and 5×104) was given using IA route. MSCs were suspended in phosphate buffered saline (PBS) and PBS alone was used for control experiments. We measured the percent change in mean laser Doppler flow signal over the ipsilateral MCA in de-escalating doses groups to determine MTD. The results demonstrated that the lowering of IA MSC dose to 1×105 and below did not compromise MCA flow and hence an IA MSC dose of 1×105 considered as MTD. Subsequently, 1 h and 24 h after rMCAo, rats were treated with IA MSCs or PBS. The 24 h delivery of IA MSCs significantly improved neurodeficit score and reduced the mean infarct volume at one month as compared to control, but not the 1 h delivery. Overall, this study suggests that the IA delivery of MSCs can be performed safely and efficaciously at the MTD of 1×105 delivered at 24 hours in rodent model of stroke.  相似文献   
99.
NADH and NADPH-ferredoxin oxidoreductases have been studied in Clostridium acetobutylicum, Cl. tyrobutyricum and Cl. pasteurianum. The study of the distribution and regulation of these enzymatic activities in well-defined culture conditions, reveals that the essential function of NADPH-ferredoxin oxidoreductase is to produce NADPH, while NADH-ferredoxin oxidoreductase can, depending on cellular conditions, produce or oxidize NADH. When these Clostridia use glycolysis, regulation of the NADH-ferredoxin oxidoreductase by acetyl-CoA (obligatory activator of NADH-ferroxin reductase activity) and by NADH (competitive inhibitor of ferredoxin-NAD+ reductase activity) allow the enzymes to function correlatively with glyceraldehyde-3-phosphate dehydrogenase and thus control the levels of NAD+ and NADH in the cell. In Cl. tyrobutyricum and Cl. pasteurianum, the ferredoxin-NADP+ reductase activities are regulated by NAD+ and NADH in accordance with the intracellular concentrations of these coenzymes. In Cl. tyrobutyricum growing on pyruvate/acetate, NADH and NADPH-ferredoxin reductase activities cannot be detected; only the ferredoxin-NAD+ and ferredoxin-NADP+ reductase activities are found. In this Clostridium, regulation of the ferredoxin-NADP+ reductase activity is the same whether it is grown on glucose or pyruvate. Contrary to this, the ferredoxin-NAD+ reductase activity undergoes a drastic change, since NADH no longer controls the enzymatic activity. In this case regulation is no longer necessary, since glyceraldehyde-3-phosphate dehydrogenase does not function.  相似文献   
100.

Background  

The local connectivity and global position of a protein in a protein interaction network are known to correlate with some of its functional properties, including its essentiality or dispensability. It is therefore of interest to extend this observation and examine whether network properties of two proteins considered simultaneously can determine their joint dispensability, i.e., their propensity for synthetic sick/lethal interaction. Accordingly, we examine the predictive power of protein interaction networks for synthetic genetic interaction in Saccharomyces cerevisiae, an organism in which high confidence protein interaction networks are available and synthetic sick/lethal gene pairs have been extensively identified.  相似文献   
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