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41.
A modular treatment of molecular traffic through the active site of cholinesterase 总被引:1,自引:0,他引:1
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We present a model for the molecular traffic of ligands, substrates, and products through the active site of cholinesterases (ChEs). First, we describe a common treatment of the diffusion to a buried active site of cationic and neutral species. We then explain the specificity of ChEs for cationic ligands and substrates by introducing two additional components to this common treatment. The first module is a surface trap for cationic species at the entrance to the active-site gorge that operates through local, short-range electrostatic interactions and is independent of ionic strength. The second module is an ionic-strength-dependent steering mechanism generated by long-range electrostatic interactions arising from the overall distribution of charges in ChEs. Our calculations show that diffusion of charged ligands relative to neutral isosteric analogs is enhanced approximately 10-fold by the surface trap, while electrostatic steering contributes only a 1.5- to 2-fold rate enhancement at physiological salt concentration. We model clearance of cationic products from the active-site gorge as analogous to the escape of a particle from a one-dimensional well in the presence of a linear electrostatic potential. We evaluate the potential inside the gorge and provide evidence that while contributing to the steering of cationic species toward the active site, it does not appreciably retard their clearance. This optimal fine-tuning of global and local electrostatic interactions endows ChEs with maximum catalytic efficiency and specificity for a positively charged substrate, while at the same time not hindering clearance of the positively charged products. 相似文献
42.
豆科黄华属植物种子表面特征的研究 总被引:2,自引:0,他引:2
在扫描电镜下观察了豆科黄华属Thermopsis 18种植物种子的表面纹饰,发现 T.alpina,T.bar-
bata,T.inflata,T.lupinoides,T. licentiana,T.smithiana和T.turkestanica的种子表面为粗网状,T
californica,T.divaricarpa,T. macrophylla,T.mollis的种子表面为细网状,T.gracilis,T.montana,T.
fabacea的种子表面为相对平滑型纹饰,T.alterniflora的种子表面为不规则条形,T.chinensis的种子表
面为粘膜状,T.rhombifolia的种子表面为条形及 T.viuosa的种子表面为碎屑状纹饰。结果表明黄华属的种子表面特征对属下类群的划分有一定意义,对澄清某些混乱的种有一定价值。 相似文献
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44.
Carla DB Fernandez Fernanda F Bellentani Glaura SA Fernandes Juliana E Perobelli Ana Paula A Favareto André F Nascimento Antonio C Cicogna Wilma DG Kempinas 《Reproductive biology and endocrinology : RB&E》2011,9(1):32
Background
Obesity is rapidly becoming a worldwide epidemic that affects children and adults. Some studies have shown a relationship between obesity and infertility, but until now it remains controversial. Thus, the aim of the present study was to investigate the effect of high-fat diet-induced obesity on male reproductive parameters. 相似文献45.
目的对长爪沙鼠线粒体ATPase8,ATPase6,COX3基因全序列进行测定,并对其进行鉴定及进化分析。方法根据长爪沙鼠已知基因序列设计引物,采用PCR产物测序法,对目的片段进行测序鉴定。结合已公布啮齿类动物ATPase8,ATPase6,COX3基因序列,分析其碱基组成、遗传距离、并基于最小进化法和UPGMA法构建系统进化树。结果获得长爪沙鼠线粒体ATPase8,ATPase6,COX3基因全序列,其与家鼠、小家鼠和仓鼠均具有较高的同源性(76~98%);进化分析结果显示,长爪沙鼠与家鼠、黑家鼠和仓鼠遗传距离较近;碱基G的含量分别为6.9%,10.7%,15.2%,符合mtDNA的特点;A+T含量分别为68.2%,64.1%,59.2%,明显低于G+C含量,符合哺乳动物的特点。结论本研究为首次获得长爪沙鼠ATPase8,ATPase6,COX3基因全序列,长爪沙鼠与家鼠、黑家鼠和仓鼠具有较近遗传距离,本研究为长爪沙鼠进化研究、线粒体的结构和功能研究奠定基础。 相似文献
46.
47.
目的调查Z:ZCLA长爪沙鼠原种群普通级长爪沙鼠的遗传多样性。方法用本实验室自行建立的长爪沙鼠19个生化基因位点的乙酸纤维素膜电泳技术并结合基本群体遗传学指标研究了普通级Z:ZCLA长爪沙鼠100个家系的遗传多态性。结果Z:ZCLA长爪沙鼠在Es-1、Car-2、Hbb、Gpi-1、Cs-1、Ce-2I、dh-l、Mod-1呈单态,在Es-2、Es-3、Es-4、Es-6、Es-8、Es-9、Es-10、pd-1、gm-1、Trf、Akp-1个位点上呈现多态性,等位基因从2~4个不等,平均等位基因数3.0,平均杂合度0.512,平均多态信息量0.455。结论提示目前本群遗传多样性水平处于中度多态。 相似文献
48.
Michelle Sait Morag Livingstone Ewan M Clark Nick Wheelhouse Lucy Spalding Bryan Markey Simone Magnino Frederick A Lainson Garry SA Myers David Longbottom 《BMC genomics》2014,15(1)
Background
Chlamydia pecorum is the causative agent of a number of acute diseases, but most often causes persistent, subclinical infection in ruminants, swine and birds. In this study, the genome sequences of three C. pecorum strains isolated from the faeces of a sheep with inapparent enteric infection (strain W73), from the synovial fluid of a sheep with polyarthritis (strain P787) and from a cervical swab taken from a cow with metritis (strain PV3056/3) were determined using Illumina/Solexa and Roche 454 genome sequencing.Results
Gene order and synteny was almost identical between C. pecorum strains and C. psittaci. Differences between C. pecorum and other chlamydiae occurred at a number of loci, including the plasticity zone, which contained a MAC/perforin domain protein, two copies of a >3400 amino acid putative cytotoxin gene and four (PV3056/3) or five (P787 and W73) genes encoding phospholipase D. Chlamydia pecorum contains an almost intact tryptophan biosynthesis operon encoding trpABCDFR and has the ability to sequester kynurenine from its host, however it lacks the genes folA, folKP and folB required for folate metabolism found in other chlamydiae. A total of 15 polymorphic membrane proteins were identified, belonging to six pmp families. Strains possess an intact type III secretion system composed of 18 structural genes and accessory proteins, however a number of putative inc effector proteins widely distributed in chlamydiae are absent from C. pecorum. Two genes encoding the hypothetical protein ORF663 and IncA contain variable numbers of repeat sequences that could be associated with persistence of infection.Conclusions
Genome sequencing of three C. pecorum strains, originating from animals with different disease manifestations, has identified differences in ORF663 and pseudogene content between strains and has identified genes and metabolic traits that may influence intracellular survival, pathogenicity and evasion of the host immune system.Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-23) contains supplementary material, which is available to authorized users. 相似文献49.
目的:改进现有的细胞冷冻保存方法,建立一个不含二甲基亚砜(DMSO)和血清(FBS)的高效冷冻保存方法,为细胞治疗等临床实践提供优质细胞.方法:海藻酸微囊包埋鼠胚成纤维细胞(STO细胞)后用不含DMSO和FBS的冷冻保存液进行冷冻保存.设四个对照组:添加10%DMSO和20%FBS的组、仅添加10%DMSO的组、仅添加20%FBS、DMSO和FBS均不添加组.在冷冻前后对各实验组细胞用台盼兰染色,进行细胞计数,计算细胞存活率,同时利用溴乙锭的二聚物(EthD)、钙黄绿素-AM(Calcein-AM)进行染色观察细胞的形态,且进一步验证细胞存活率;解冻复苏后用MTT法评估细胞的增殖速度和生长活力.结果:冷冻保存30天后对各组的细胞数量、细胞存活率、细胞形态和解冻复苏后细胞的生长活力进行比较发现,海藻酸微囊包埋冷冻组的细胞数、细胞存活率、细胞形态和生长活力均与添加DMSO和FBS的组之间无显著性差异,而与其它三个对照组呈显著性差异.结论:使用海藻酸微囊替代DMSO和FBS保存STO细胞,能有效的维持细胞形态、数量、存活率,同时不影响细胞的生长活力,从而建立了一个不含DMSO和FBS的高效冷冻保存方法. 相似文献
50.
H-FABP基因的多态性和营养因素对猪肉质的影响 总被引:4,自引:0,他引:4
遗传和营养因素都能影响猪肉的品质。但是, 到目前为止同时研究遗传和营养因素对肉质影响的报道很少。在本研究中, 136头PIC5系杂交猪, 体重65 kg, 被随机分成4组, 各组分别给予不同日粮。在饲养35 d、体重大约90 kg时统一屠宰并且进行肉质测定、H-FABP基因分型及其与肉质性状的关联分析。结果表明: (1)所采用的3种日粮对肉色、屠宰后24 h的pH、肌内脂肪和肌肉蛋白含量有极显著的影响; (2)H-FABP基因型对肌内脂肪和肌肉蛋白含量存在极显著的影响; (3)H-FABP基因多态性和营养因素的交互作用对pH 和肌内脂肪含量均有显著的影响, 对照组的AA基因型具有最高pH值, 高维生素E组的AA基因型具有最高肌内脂肪值。实验结果提示在关于猪肉质的育种和生产过程中应该同时考虑营养因素和遗传因素。 相似文献