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排序方式: 共有609条查询结果,搜索用时 15 毫秒
1.
B K S?min A L Bautina I I Ivanov 《Nauchnye doklady vysshe? shkoly. Biologicheskie nauki》1989,(5):32-36
The effect of substances of different nature on the thermodynamic characteristics of dimyristoylphosphatidylcholine (DMPC) phase transition by the differential scanning microcalorimetry has been studied. The substances disposed in hydrophobic part of membrane--alpha-tocopherol, ubiquinone Q10, ionol and vitamin K3 cause the decrease of enthalpy and cooperativity of phase transition. The substances which have the side hydrocarbon chain (tocopherol and ubiquinone Q10) compared with ones without it (ionol and vitamin K3) and reduced quinones (Q10 and vitamin K3) compared with the oxidized ones have stronger influence on the enthalpy and cooperativity of transition. The inclusion of the local anesthetic dicaine disposed mainly in the zone of polar heads of phospholipids into DMPC membranes decreases the temperature of phase transition considerably and practically does not change the cooperativity. A possibility to use the method of differential scanning microcalorimetry to estimate the localization of membrane tropic substances within lipid bilayer is under discussion. 相似文献
2.
Effect of pH on the activity of proteinases in intestinal mucosa,chyme, and microbiota of fish from the Cuciurgan reservoir 总被引:1,自引:0,他引:1
Proteolytic activities of the intestinal mucosa, chyme, and enteral microbiota have been studied in a wide range of pH values in five fish species from the Cuciurgan reservoir (Moldova). Differences in pH dependence of the intestinal proteinase activity of fish are determined by their feeding type. The maximum activity of proteinases is found in the pumpkinseed Lepomis gibbosus. The minimum activity of proteinases has been demonstrated by the zander Zander lucioperca. The pH optimum of the mucosa and chyme in all fish species (except for the European perch Perca fluviatilis) is 10. The pH optimum of the intestinal microflora varies from 6.0 (in the common carp Cyprinus carpio) to 10 (in the crucian carp Carassius carassius), whereas that in the perch from the Cuciurgan and Rybinsk reservoirs is 7. The majority of fish species, mostly Zander lucioperca and Lepomis gibbosus, are characterized by high proteniase activity of the microbiota, in the pH ranging from 6 to 9. It is assumed that proteinases in the enteral microbiota of fish are able to make up for the relatively low activity of those synthesized by their digestive system in the range of low pH values. 相似文献
3.
Some properties of the β-N-acetyl-D-hexosaminidase purified from intercellular fluid of tomato leaves after the plant was systematically infected by TMV (tobacco mosaic virus) were studied. When pNP β-D-GlcNAc (p nitrophenyl-N-aeetyl β-D-glucosaminide) or pNP β-D- GalNAc (p-nitrophenyl-N-acetyl-β-D galactosaminide) was used as the substrate, it showed the optical pH between 4. 8--5.0 and optical temperature between 44— 47℃. Studies of thermostabillty indicated that the enzyme had a biphasic denaturation curve. Using pNP-β-D-GIcNAc or pNP-β-D GalNAc as the substrate, the Km value of the enzyme was 0. 36 and 0. 67 mmol/L respectively. N acetyi-D glucosamine and N acetyl-D-galactosamine were competitive inhibitors of the enzyme activities. Ag+ and Hg2+ were sensitive inhibitors and Fe2+ . Fe3+ and Cu2+ were also inhibitors enzyme activities. 相似文献
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6.
宁夏蝗虫地理分布格局的聚类分析 总被引:10,自引:1,他引:10
根据宁夏的自然环境和行政区划将宁夏分为22个分布区域。为方便聚类分析,根据分布范围将宁夏蝗虫分为全布种(22个区域有分布)、多布种(2~21区域有分布)和独布种(只分布在1个区域)3类。在以分布区域为特征做聚类分析的基础上,把多布种分组并确定重叠的分布格局,共分为14个组。各组蝗虫在宁夏的自然分布作为其分布格局。结果表明:宁夏蝗虫的多布种多呈不连续分布;分布格局与国内外基本相似;贺兰山是宁夏蝗虫分布的热点。不连续的环境是造成宁夏蝗虫多布种不连续分布的主要原因。 相似文献
7.
吸湿—回干处理降低番茄种子电解质渗漏的机理研究 总被引:3,自引:3,他引:3
对吸湿-回干处理降低番茄种子电解质渗漏的机理进行了研究,结果表明,吸湿-回干处理降低番茄种子电解质渗漏的效应产生于吸湿阶段。随吸湿时间延长,电解质渗漏下降,而SOD、CAT活性上升。mRNA和蛋白质合成抑制对剂电解质渗漏下降与SOD、CAT活性上升均无抑制作用,表明吸湿处理降低电解质渗漏、提高SOD、CAT活性的作用mRNA和蛋白质合成无关,吸湿和吸湿-回干处理后K3Fe(CN)6还原活显著下降,表明的生理生化状态发生了某种变化。 相似文献
8.
Evolutionary origin of human and primate malarias: evidence from the circumsporozoite protein gene 总被引:7,自引:1,他引:7
We have analyzed the conserved regions of the gene coding for the
circumsporozoite protein (CSP) in 12 species of Plasmodium, the malaria
parasite. The closest evolutionary relative of P. falciparum, the agent of
malignant human malaria, is P. reichenowi, a chimpanzee parasite. This is
consistent with the hypothesis that P. falciparum is an ancient human
parasite, associated with humans since the divergence of the hominids from
their closest hominoid relatives. Three other human Plasmodium species are
each genetically indistinguishable from species parasitic to nonhuman
primates; that is, for the DNA sequences included in our analysis, the
differences between species are not greater than the differences between
strains of the human species. The human P. malariae is indistinguishable
from P. brasilianum, and P. vivax is indistinguishable from P. simium; P.
brasilianum and P. simium are parasitic to New World monkeys. The human P.
vivax-like is indistinguishable from P. simiovale, a parasite of Old World
macaques. We conjecture that P. malariae, P. vivax, and P. vivax-like are
evolutionarily recent human parasites, the first two at least acquired only
within the last several thousand years, and perhaps within the last few
hundred years, after the expansion of human populations in South America
following the European colonizations. We estimate the rate of evolution of
the conserved regions of the CSP gene as 2.46 x 10(-9) per site per year.
The divergence between the P. falciparum and P. reichenowi lineages is
accordingly dated 8.9 Myr ago. The divergence between the three lineages
leading to the human parasites is very ancient, about 100 Myr old between
P. malariae and P. vivax (and P. vivax-like) and about 165 Myr old between
P. falciparum and the other two.
相似文献
9.
白色念珠菌蛋白酶与其毒力关系的研究 总被引:20,自引:2,他引:20
目的 探讨白色念珠菌蛋白酶活动与其毒力关系。方法的采用牛奶平地检测54株白色念珠菌蛋白酶的分泌能力,然后选择6侏菌分别经摇瓶培养测定其蛋白酶活力,并以静脉内注射方式感染小鼠进行毒力试验,以小鼠平均生存时间来评价菌株毒力。结果 54株白色念珠菌全部能分泌蛋白酶,检出率为100%。动物试验表明蛋白酶活力愈高的菌株,相应小鼠平均生存时间愈短;蛋白酶活力与菌株毒力直接正相关(γ=0.934,P<0.01) 相似文献
10.
Nicolas Galtier Richard W. Jobson Beno?t Nabholz Sylvain Glémin Pierre U. Blier 《Biology letters》2009,5(3):413-416
The evolutionary rate of mitochondrial DNA (mtDNA) is highly variable across lineages in animals, and particularly in mammals. This variation has been interpreted as reflecting variations in metabolic rate: mitochondrial respiratory activity would tend to generate mutagenic agents, thus increasing the mutation rate. Here we review recent evidence suggesting that a direct, mechanical effect of species metabolic rate on mtDNA evolutionary rate is unlikely. We suggest that natural selection could act to reduce the (somatic) mtDNA mutation rate in long-lived species, in agreement with the mitochondrial theory of ageing. 相似文献