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991.
Sequencing and Expression of Additional Xylanase Genes from the Hyperthermophile Thermotoga maritima FjSS3B.1 下载免费PDF全文
Rosalind A. Reeves Moreland D. Gibbs Daniel D. Morris Katherine R. Griffiths David J. Saul Peter L. Bergquist 《Applied microbiology》2000,66(4):1532-1537
Two genes, xynB and xynC, coding for xylanases were isolated from Thermotoga maritima FjSS3B.1 by a genomic-walking–PCR technique. Sequencing of the genes showed that they encode multidomain family 10 xylanases. Only XynB exhibited activity against xylan substrates. The temperature optimum (87°C) and pH optimum (pH 6.5) of XynB are different from the previously reported xylanase, XynA (also a family 10 enzyme), from this organism. The catalytic domain expressed without other domains has a lower temperature optimum, is less thermostable, and has optimal activity at pH 6.5. Despite having a high level of sequence similarity to xynB, xynC appears to be nonfunctional since its encoded protein did not show significant activity on xylan substrates. 相似文献
992.
Alison Colquhoun Simon Alaluf Adrian Bradley Natasha Gemmell Gary Gibbs Helen M. I. Osborn Laurence M. Harwood Eric A. Newsholme 《Cell biochemistry and function》1997,15(4):243-249
The effects of several novel monosaccharides upon thymidine incorporation into both normal and tumour cells were investigated. The monosaccharide 2-deoxy-3-[1-(R)-(ethoxycarbonyl)ethyl]-α-D -allo-pyranose had the most inhibitory effect on proliferation, with the (S)-enantiomer having less inhibitory effects. The chiral centre at carbon-7 was found to be an important part of the molecule, as 2-deoxy-3-[methoxycarbonyl methyl]-α-D -allo-pyranose had greatly decreased anti-proliferative properties in comparison with the parent compound. In addition, the 2-deoxy structure at carbon-2 was also found to be important, as 3-[1-(S)-(ethoxycarbonyl)ethyl]-α-D -allo-hexopyranose had greatly decreased inhibitory properties in comparison with the parent compound. The results indicate that these novel monosaccharides possess potent anti-proliferative properties, related to their chiral carbon-7 and 2-deoxy carbon-2 structure and suggest that further substitutions of the functional group at carbon-7 may improve these properties and possibly produce inhibitor selectivity for tumour cells in preference to normal cells. © 1997 John Wiley & Sons, Ltd. 相似文献
993.
Effect of Lyophilization and Freeze-thawing on the Stability of siRNA-liposome Complexes 总被引:1,自引:0,他引:1
The purpose of this research was to describe the application of lyophilization in the delivery of siRNA using cationic lipids
by addressing the long-term formulation/stability issues associated with cationic lipids and to understand the mechanism of
lyoprotection. siRNA liposomes complexes were formed in different potential cyro/lyoprotectants and subjected to either lyophilization
or freeze thaw cycles. siRNA, liposomes and/or lipoplexes were tested for activity, SYBR Green I binding, cellular uptake
and particle size. The lipoplexes when lyophilized in the presence of sugars as lyoprotectants could be lyophilized and reconstituted
without loss of transfection efficacy but in ionic solutions they lost 65–75% of their functionality. The mechanism of this
loss of activity was further investigated. The lyophilization process did not alter siRNA’s intrinsic biological activity
as was evident by the ability of lyophilized siRNA to retain functionality and SYBR green I binding ability. While the lipoplex
size dramatically increased (∼50–70 times) after lyophilization in the absence of non-ionic lyoprotectants. This increase
in size correlated to the decrease in cellular accumulation of siRNA and a decrease in activity. In conclusion, siRNAs can
be applied in cationic lipid lyophilized formulations and these complexes represent a potential method of increasing the stability
of pre-formed complex. 相似文献
994.
The rat genome project and the resources that it has generated are transforming the translation of rat biology to human medicine. The rat genome was sequenced to a high quality "draft," the structure and location of the genes were predicted, and a global assessment was published (Gibbs RA et al., Nature 428: 493-521, 2004). Since that time, researchers have made use of the genome sequence and annotations and related resources. We take this opportunity to review the currently available rat genome resources and to discuss the progress and future plans for the rat genome. 相似文献
995.
996.
T M Ciccarone S C MacTough T M Williams C J Dinsmore T J O'Neill D Shah J C Culberson K S Koblan N E Kohl J B Gibbs A I Oliff S L Graham G D Hartman 《Bioorganic & medicinal chemistry letters》1999,9(14):1991-1996
The design and syntheses of non-thiol inhibitors of farnesyl-protein transferase are described. Substitutions on an imidazolylmethyl-AMBA-methionine template gave a highly potent and cell-active inhibitor. 相似文献
997.
G W Gould G E Lienhard L I Tanner E M Gibbs 《Archives of biochemistry and biophysics》1989,268(1):264-275
Phenylarsine oxide (PAO) has been shown to exert a biphasic effect on glucose transport in 3T3-L1 adipocytes. At 10 microM, PAO activates transport threefold, but at higher concentrations an inhibition of transport is observed. In this paper we report a procedure for the subcellular fractionation of these cells which we use to examine the distribution of glucose transporters following PAO challenge. Quantitative immunoblotting showed that the glucose transporter content of the plasma membrane fraction increased with increasing PAO concentrations; a parallel increase in another insulin-responsive protein, the transferrin receptor, also occurred. However, cell-surface labeling procedures for the glucose transporter and transferrin receptor showed that PAO actually decreased the cell-surface concentrations of these proteins; the basis of this discrepancy may be that in the presence of PAO, intracellular vesicles containing these proteins associate with the plasma membrane, but do not fuse with it. The possibility that PAO modulated transport by direct interaction with the glucose transporter was investigated by examining the effects of PAO on transport in both erythrocytes and a reconstituted system of purified erythrocyte transporter in lipid vesicles. PAO was without effect on the rate of transport in these systems. The hypothesis that the stimulatory effect of PAO on transport might be due to the activation of the insulin receptor kinase activity was examined by assessing the phosphotyrosine content of the receptor and other proteins using anti-phosphotyrosine antibodies. PAO alone caused no detectable increase in receptor phosphotyrosine content. However, the combination of PAO and insulin led to the tyrosine phosphorylation of two proteins of Mr 68,000 and 57,000 which were not detected in cells treated with either PAO or insulin, and an increased phosphotyrosine content of proteins of Mr 95,000 and 165,000 when compared to cells treated with insulin alone. 相似文献
998.
Localization of the Enzymes Involved in the Photoevolution of H(2) from Acetate in Chlamydomonas reinhardtii 总被引:1,自引:5,他引:1 下载免费PDF全文
The localization of a series of enzymes involved in the anaerobic photodissimilation of acetate in Chlamydomonas reinhardtii F-60 adapted to a hydrogen metabolism was determined through the enzymic analyses of the chloroplastic, cytoplasmic, and mitochondrial fractions obtained with a cellular fractionation procedure that incorporated cell wall removal by treatment with autolysine, digestion of the plasmalemma with the detergent digitonin, and fractionation by differential centrifugation on a Percoll step gradient. The sequence of events leading to the photoevolution of H2 from acetate includes the conversion of acetate into succinate via the extraplastidic glyoxylate cycle, the oxidation of succinate to fumarate by chloroplastic succinate dehydrogenase, and the oxidation of malate to oxaloacetate in the chloroplast by NAD dependent malate dehydrogenase. The level of potential activity for the enzymes assayed were sufficient to accommodate the observed rate of the photoanaerobic dissimilation of acetate and the photoevolution of H2. 相似文献
999.
Background
Indels are an important cause of human variation and central to the study of human disease. The 1000 Genomes Project Low-Coverage Pilot identified over 1.3 million indels shorter than 50 bp, of which over 890 were identified as potentially disruptive variants. Yet, despite their ubiquity, the local genomic characteristics of indels remain unexplored.Results
Herein we describe population- and minor allele frequency-based differences in linkage disequilibrium and imputation characteristics for indels included in the 1000 Genomes Project Low-Coverage Pilot for the CEU, YRI and CHB+JPT populations. Common indels were well tagged by nearby SNPs in all studied populations, and were also tagged at a similar rate to common SNPs. Both neutral and functionally deleterious common indels were imputed with greater than 95% concordance from HapMap Phase 3 and OMNI SNP sites. Further, 38 to 56% of low frequency indels were tagged by low frequency SNPs. We were able to impute heterozygous low frequency indels with over 50% concordance. Lastly, our analysis also revealed evidence of ascertainment bias. This bias prevents us from extending the applicability of our results to highly polymorphic indels that could not be identified in the Low-Coverage Pilot.Conclusions
Although further scope exists to improve the imputation of low frequency indels, our study demonstrates that there are already ample opportunities to retrospectively impute indels for prior genome-wide association studies and to incorporate indel imputation into future case/control studies. 相似文献1000.
Arne Moksnes Eivin Røskaft Geir Rudolfsen Sigrun Skjelseth Bård G. Stokke Oddmund Kleven H. Lisle Gibbs Marcel Honza Barbara Taborsky Yvonne Teuschl Wolfgang Vogl Michael Taborsky 《Journal of avian biology》2008,39(2):238-241
Females of the obligate brood parasitic common cuckoo Cuculus canorus are assumed to lay eggs of consistent colour and pattern and egg characteristics have been used to separate between different individuals. We tested the "constant egg-type hypothesis" in blind tests using test persons who grouped cuckoo eggs into "potential clutches" based on similarity in appearance. A correct classification of eggs laid by known (radiotagged) females supported the hypothesis. However, comparisons between maternity based on visual assessments and DNA-based parentage analyses revealed rather poor concordance between the two methods. Our findings indicate that egg characteristics cannot be used to separate between cuckoo females, even if they lay eggs with constant appearance. The reason is probably that there are only small or negligible variations in egg appearance between some females like mothers and daughters or other closely related individuals. 相似文献