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排序方式: 共有286条查询结果,搜索用时 171 毫秒
31.
Sørensen KW Nicolaes GA Villoutreix BO Yamazaki T Tans G Rosing J Dahlbäck B 《Biochemistry》2004,43(19):5803-5810
Activated coagulation factor V (FVa) is a cofactor of activated factor X (FXa) in prothrombin activation. FVa is composed of a light chain (LC) and a heavy chain (HC) that are noncovalently associated in a calcium-dependent manner. We constructed a recombinant FV Asp111Asn/Asp112Asn mutant (rFV-NN) to abolish calcium binding to a potential calcium-binding site in FVa in order to study the specific role of these residues in the expression of FVa activity. Whereas thrombin-activated recombinant FV wild type (rFV-wt) presented with stable FVa activity, incubation of rFV-NN with thrombin resulted in a temporary increase in FVa activity, which was rapidly lost upon prolonged incubation. Loss of FVa activity was most likely due to dissociation of HC and LC since, upon chromatography of rFVa-NN on a SP-Sepharose column, the HC did not bind significantly to the resin whereas the LC bound and could be eluted at high ionic strength. In contrast, rFVa-wt adhered to the column, and both the HC and LC coeluted at high ionic strength. In the presence of phospholipid vesicles, the loss of rFVa-NN activity was partially prevented by FXa, active site inhibited FXa, and prothombin in a dose-dependent manner. We conclude that the introduced amino acid substitutions result in a loss of the high-affinity (calcium-dependent) interaction of the HC and LC of FVa. We propose that the introduced substitutions disrupt the calcium-binding site in FV, thereby yielding a FV molecule that rapidly loses activity following thrombin-catalyzed activation most likely via dissociation of the HC and LC. 相似文献
32.
Horikawa Y Morohashi T Sano T Sakai N Yamada S Sasa R 《Biological trace element research》2006,112(3):263-271
We examine the effects of fructooligosaccharides (FOS) on the reduction in the incisor iron content in gastrectomized rat.
Twenty-eight 5-wk-old male Sprague-Dawley rats were divided into two groups: sham operated (bSH) and gastrectomized (bGX).
After 4 wk each group was divided into two subgroups according to the presence or absence of 7.5% FOS in the synthetic diet
(SH, SH+FOS, GX, and GX+FOS). At 10 wk wafter surgery, the maxilla was prepared to examine the iron content of the incisor
enamel surface at four points. These points corresponded to the iron content at 6,7,8, and 10 wk, respectively. Blood was
collected to determine serum iron levels at 4 and 10 wk. The serum iron level significantly decreased at 4 and 10 wk the GX
group. At 10 wk, the level in the GX+FOS group significantly increased but did not reaach that in the SH group. The iron content
of the enamel surface time-dependently increased and no significant differences were seen between SH and GX+FOS at 8 and 10
wk. These results suggest that FOS consumption impaired the loss of enamel content following gastrectomy, and this effect
preceded the effect on the serum iron level. 相似文献
33.
da Costa da Santos EK Honda RT Nozawa SR Ferreira-Nozawa MS 《Genetics and molecular biology》2012,35(1):134-141
Analysis of bacterial diversity in soils along the banks of the Solimões and
Negro rivers, state of Amazonas, Brazil, was by partial sequencing of the genes codifying
the rDNA16S region. Diversity of operational taxonomic units (OTU) and of the divergent
sequences obtained were applied in comparative analysis of microbiological diversity in
the two environments, based on richness estimators and OTU diversity indices. The higher
OTU diversity in the Solimões was based on the higher number of parameters that
evoke this. The interaction between the nucleotide sequences of bacteria inhabiting the
two riverine environments indicated that the two microrganism communities are similar in
composition. 相似文献
34.
GM1 epitope tetrasaccharide was synthesized by a condensation of sialyl-alpha(2-3)-gal acceptor and gal-beta(1-3)-GalN donor in a highly efficient manner. After introduction of mercaptohexanol to the tetrasaccharide, it was coupled to maleimide-activated KLH carrier protein to give the desired GM1 epitope-KLH conjugate. 相似文献
35.
We have obtained the first momentary photographs of sperms just as they are discharged from the antheridium of a liverwort,
Conocephalum conicum, and have succeeded in monitoring the airborne sperms of bryophytes under field conditions. Airborne sperm of liverworts
seems to be an effective strategy for raising the efficiency of fertilization between male and female plants separated in
a drought environment.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
36.
37.
Koji Morita Chikako Hasegawa Masakatsu Kaneko Shinya Tsutsumi Junko Sone Tomio Ishikawa Takeshi Imanishi Makoto Koizumi 《Bioorganic & medicinal chemistry letters》2002,12(1):73-76
To develop antisense oligonucleotides, novel nucleosides, 2'-O,4'-C-ethylene nucleosides and their corresponding phosphoramidites, were synthesized as building blocks. The 1H NMR analysis showed that the 2'-O,4'-C-ethylene linkage of these nucleosides restricts the sugar puckering to the N-conformation as well as the linkage of 2'-O,4'-C-methylene nucleosides which are known as bridged nucleic acids (BNA) or locked nucleic acids (LNA). The ethylene-bridged nucleic acids (ENA) showed a high binding affinity for the complementary RNA strand (DeltaT(m)=+5.2 degrees C/modification) and were more nuclease-resistant than natural DNA and BNA/LNA. These results indicate that ENA have better properties as antisense oligonucleotides than BNA/LNA. 相似文献
38.
Cell walls were isolated by sonic disruption of log-phase cells of Clostridium botulinum type A strain 190L and purified by treatment with sodium dodecyl sulfate (SDS) followed by digestion with proteases. Electron microscopy revealed that the cell walls thus obtained were free of both cytoplasmic membrane and cytoplasmic fragments. The purified cell wall contained 8.7% total nitrogen, 15.0% total hexosamines, 22.4% reducing groups, 8.3% carbohydrate, and 3.1% glucose. The content of total phosphorus was very low (0.02%), and therefore it was expected that teichoic acid might be absent in the cell wall. The wall peptidoglycan contained glutamic acid, alanine, diaminopimelic acid, glucosamine and muramic acid in the molar ratios of 1.00:1.85:0:85:1.06:0.67. A low amount of galactosamine was also present, but no other amino acids were found in significant quantities. The SDS-treated cell walls were not attacked by lysozyme, but after extraction with hot formamide they were completely dissolved by the enzyme and released reducing groups. The lysozyme digest was separated into two constituents, the saccharide moiety and the peptide moiety on Sephadex G-50. 相似文献
39.
40.
To clarify when the cholinergic receptor-mediated secretion mechanism of developing adrenal chromaffin cells is expressed and becomes functional, morphological changes and intracellular calcium dynamics were studied by immunohistochemistry, electron microscopy, and Fura-2 digital image analysis. From embryonic day 14 to 16, adrenal medullary cells were immunoreactive to noradrenaline-synthesizing enzyme (dopamine β-hydroxylase) but not to adrenaline-synthesizing enzyme (phenylethanolamine N-methyltransferase). These cells contained either no granules or just a few granules of high electron density. Exocytotic figures were rarely observed in cells of the control or in cells after carbamylcholine stimulation. Nerve fibers in the adrenal medulla contained either no clear vesicles or very few. Neither methacholine nor nicotine caused a change of intracellular Ca2+ in most chromaffin cells. From embryonic day 18 to 20, chromaffin cells were immunoreactive to both dopamine β-hydroxylase and phenylethanolamine N-methyltransferase and they contained relatively numerous secretory granules. Exocytotic figures were often seen in cells after carbamylcholine stimulation. The intra-adrenal nerve fibers contained numerous clear vesicles and a few dense-cored vesicles. Methacholine caused no rise of intracellular Ca2+, but nicotine induced a low to relatively high rise in many cells. From postnatal day 2 or 3 to postnatal week 1, numerous cells were immunoreactive to both dopamine β-hydroxylase and phenylethanolamine N-methyltransferase, whereas some cells were reactive to dopamine β-hydroxylase alone. Chromaffin cells were divisible into noradrenaline cells and adrenaline cells based on the ultrastructural features of their granules. Methacholine induced a moderate rise of intracellular Ca2+ and nicotine caused a high rise in many chromaffin cells, whereas, in some chromaffin cells, methacholine induced no rise of intracellular Ca2+ and nicotine induced a high rise. These results suggest that morphological changes of the developing cells and the intra-adrenal nerve fibers are related to the expression of a cholinergic receptor-mediated secretion mechanism and that this mechanism via a nicotinic receptor-mediated Ca2+ signaling pathway precedes the muscarinic receptor-mediated one during development. 相似文献