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991.
由高分子反应统计理论,结合~1H-NMR及(13)C-NMR方法,分析了T902抗泡剂的序列结构,获得了该三元无规共聚物分子的链段分布函数。系统研究了分子结构对消泡性能的影响,指出了改善抗泡剂配伍性能的正确途径。 相似文献
992.
以BANA为废物,对草鱼胰蛋白酶最适温度、最适pH以及K_m与V_(max)进行了研究,并对这些因素与饲料的关系进行了探讨。 相似文献
993.
针对具有广泛应用的Walsh-Hadamard变换,研究了适合其ASIC设计的算法与SFG阵列结构、位串计算、可变长功能等方面的内容,并给出了Walsh-Hadamard变换ASIC的一种合理结构。 相似文献
994.
提出了能够将任一长序列变换有效地分解为一组定长的短序列变换的方法及算法,通过用短序列芯片计算这些短序列变换,从而可高速完成任意长序列的变换。 相似文献
995.
Sex in Caenorhabditis elegans is determined by a regulatory cascade of seven interacting autosomal genes controlled by three X-linked genes in response to the X chromosome-to-autosome (X/A) ratio. XX animals (high X/A) develop as self-fertile hermaphrodites, and XO animals (low X/A) develop as males. The activity of the first gene in the sex-determining cascade, her-1, is required for male sexual development. XO her-1 loss-of-function mutants develop as self-fertile hermaphrodites, whereas XX her-1 gain-of-function mutants develop as masculinized intersexes. By genetic mosaic analysis using a fused free duplication linking her-1 to a cell-autonomous marker gene, we show here that her-1 expression in a sexually dimorphic cell is neither necessary nor sufficient for that cell to adopt a male fate. Our results suggest that her-1 is expressed in many, possibly all, cells and that its gene product can function non-autonomously through cell interactions to determine male sexual development. 相似文献
996.
报道了一种新的以石油醚—氯仿—异两醇(79:20:1)三元体系为展开剂,分离叶绿体色素的单向纸色谱法,能够完全分离高等植物中常见的六种叶绿体色素,叶绿素a、叶绿素b、β-胡萝卜素、叶黄素、紫黄质、新黄质和一种叶绿素a的衍生物脱植基叶绿素a。 相似文献
997.
The hormone insulin is stored in secretory granules and released from the pancreatic beta-cells by exocytosis. In the consensus model of glucose-stimulated insulin secretion, ATP is generated by mitochondrial metabolism, promoting closure of ATP-sensitive potassium (KATP) channels, which depolarizes the plasma membrane. Subsequently, opening of voltage-sensitive Ca2+ channels increases the cytosolic Ca2+ concentration ([Ca2+]c) which constitutes the main trigger initiating insulin exocytosis. Nevertheless, the Ca2+ signal alone is not sufficient for sustained secretion. Furthermore, glucose elicits a secretory response under conditions of clamped, elevated [Ca2+]c. A mitochondrial messenger must therefore exist which is distinct from ATP. We have now identified this as glutamate. We show that glucose generates glutamate from beta-cell mitochondria. A membrane-permeant glutamate analogue sensitizes the glucose-evoked secretory response, acting downstream of mitochondrial metabolism. In permeabilized cells, under conditions of fixed [Ca2+]c, added glutamate directly stimulates insulin exocytosis, independently of mitochondrial function. Glutamate uptake by the secretory granules is likely to be involved, as inhibitors of vesicular glutamate transport suppress the glutamate-evoked exocytosis. These results demonstrate that glutamate acts as an intracellular messenger that couples glucose metabolism to insulin secretion. 相似文献
998.
Identification of in vivo substrates of the chaperonin GroEL 总被引:22,自引:0,他引:22
999.
1000.
Sequence and analysis of chromosome 2 of the plant Arabidopsis thaliana 总被引:21,自引:0,他引:21
Lin X Kaul S Rounsley S Shea TP Benito MI Town CD Fujii CY Mason T Bowman CL Barnstead M Feldblyum TV Buell CR Ketchum KA Lee J Ronning CM Koo HL Moffat KS Cronin LA Shen M Pai G Van Aken S Umayam L Tallon LJ Gill JE Adams MD Carrera AJ Creasy TH Goodman HM Somerville CR Copenhaver GP Preuss D Nierman WC White O Eisen JA Salzberg SL Fraser CM Venter JC 《Nature》1999,402(6763):761-768
Arabidopsis thaliana (Arabidopsis) is unique among plant model organisms in having a small genome (130-140 Mb), excellent physical and genetic maps, and little repetitive DNA. Here we report the sequence of chromosome 2 from the Columbia ecotype in two gap-free assemblies (contigs) of 3.6 and 16 megabases (Mb). The latter represents the longest published stretch of uninterrupted DNA sequence assembled from any organism to date. Chromosome 2 represents 15% of the genome and encodes 4,037 genes, 49% of which have no predicted function. Roughly 250 tandem gene duplications were found in addition to large-scale duplications of about 0.5 and 4.5 Mb between chromosomes 2 and 1 and between chromosomes 2 and 4, respectively. Sequencing of nearly 2 Mb within the genetically defined centromere revealed a low density of recognizable genes, and a high density and diverse range of vestigial and presumably inactive mobile elements. More unexpected is what appears to be a recent insertion of a continuous stretch of 75% of the mitochondrial genome into chromosome 2. 相似文献