The structure of Staphylococcus aureus alpha-toxin-induced ionic channel

Polyethylene glycols (PEG) with molecular weight less than or equal to 3000 were shown to effectively protect human erythrocytes from osmotic lysis induced by alpha-staphylotoxin (ST). PEG with MW less than 3000 do not change the conductivity of ion channels induced by ST in bilayer lipid membranes (BLM). Changing the bilayer from a pure phosphatidylcholine (PC) to a negatively charged phosphatidylserine (PS) film results in an asymmetry of the current-voltage characteristics. This is evidenced by the asymmetrical position of the ST-channel pore in bilayer membranes. The results obtained allow to conclude that the ST-channel is an interprotein pore filled with water (with an inner diameter of 2.5-3 nm and a length of approximately 10 nm). It is composed of six molecules of alpha-toxin from Staphylococcus aureus. The ST-channel incorporates into a membrane with only one mouth in contact with the polar lipid heads and the other one protruding 4.5-5 nm from the bilayer plane in water solution.     

Cation-anion selectivity and conductivity of the channels formed by black widow spider whole venom in lipid bilayer

It is established that BWSV (black widow spider venom) is capable of forming ion channels in lipid bilayer (BPhM). This effect is minimal upon pH value close to 5.0 and is increased either upon oxidation or alkalization of the medium. The amplitudes of the channels are monotonously decreased upon the reduction of pH with simultaneous narrowing of their dispersion. The degree of the change of BPhM conductivity by concentration of BWSV is close to 2 at different pH. Apparently the absorption of the active component of venom on bilayer surface is accompanied by doubling of the degree of its aggregation. Almost ideal cation selectivity of BWSV channels (pH 7.5) is significantly decreased upon the increase in ionic strength. Ionic channel is thought to be a zone of interaction of lipid domains. Possible structure of such a channel is discussed.     

Properties of the channels induced by Lityphantes paykullianus venom

It was found that common venom of Lityphantes paykullianus is capable of forming conductivity channels on bilayer phospholipid membrane. The values of channel conductivity are remarkably distinguished in the solutions of different alkaline metals. The selectivity of channels is mainly cationic at pH 7.5 with weak discrimination of ions few tell one from the other by size. These results indicate that there is an active component in the common venom accountable for channels formation.     

中国西北沙漠夜间活动的东鳖甲属昆虫二新种(鞘翅目:拟步甲科:漠甲亚科)

记述中国西北地区东鳖甲属2新种:巴丹东鳖甲A.badainica Ba,Ren&Liu sp.nov.和古尔班东鳖甲A.gurbantunggutica Ba&Ren sp.nov.,提供了主要鉴别特征和形态图,并简要讨论了其昼夜活动规律.     

Haemosporidian Parasites of Antelopes and Other Vertebrates from Gabon,Central Africa

Re-examination, using molecular tools, of the diversity of haemosporidian parasites (among which the agents of human malaria are the best known) has generally led to rearrangements of traditional classifications. In this study, we explored the diversity of haemosporidian parasites infecting vertebrate species (particularly mammals, birds and reptiles) living in the forests of Gabon (Central Africa), by analyzing a collection of 492 bushmeat samples. We found that samples from five mammalian species (four duiker and one pangolin species), one bird and one turtle species were infected by haemosporidian parasites. In duikers (from which most of the infected specimens were obtained), we demonstrated the existence of at least two distinct parasite lineages related to Polychromophilus species (i.e., bat haemosporidian parasites) and to sauropsid Plasmodium (from birds and lizards). Molecular screening of sylvatic mosquitoes captured during a longitudinal survey revealed the presence of these haemosporidian parasite lineages also in several Anopheles species, suggesting a potential role in their transmission. Our results show that, differently from what was previously thought, several independent clades of haemosporidian parasites (family Plasmodiidae) infect mammals and are transmitted by anopheline mosquitoes.     

Molecular basis of ion permeability in a voltage‐gated sodium channel

Voltage‐gated sodium channels are essential for electrical signalling across cell membranes. They exhibit strong selectivities for sodium ions over other cations, enabling the finely tuned cascade of events associated with action potentials. This paper describes the ion permeability characteristics and the crystal structure of a prokaryotic sodium channel, showing for the first time the detailed locations of sodium ions in the selectivity filter of a sodium channel. Electrostatic calculations based on the structure are consistent with the relative cation permeability ratios (Na⁺ ≈ Li⁺ ≫ K⁺, Ca²⁺, Mg²⁺) measured for these channels. In an E178D selectivity filter mutant constructed to have altered ion selectivities, the sodium ion binding site nearest the extracellular side is missing. Unlike potassium ions in potassium channels, the sodium ions in these channels appear to be hydrated and are associated with side chains of the selectivity filter residues, rather than polypeptide backbones.     

Efficacy of hyaluronic acid binding assay in selecting motile spermatozoa with normal morphology at high magnification

Background  

The present study aimed to evaluate the efficacy of the hyaluronic acid (HA) binding assay in the selection of motile spermatozoa with normal morphology at high magnification (8400x).     

基于ISSR标记的辽宁4个东北林蛙种群遗传多样性分析

辽宁是东北林蛙Rana dybowskii主要分布地之一,种群数量巨大,其群体遗传多样性有待评估.本研究应用ISSR标记技术对东北林蛙4个种群105个样本进行研究,5个引物共获得44条清晰谱带,4个种群的多态位点率均大于75%,Nei's基因多样性为0.2851,Shannon信息指数为0.4476,显示了较高的遗传多样性.对遗传分化系数、Nei's遗传距离、AMOVA分子变异巢式方差分析和F-统计量等遗传参数的统计结果表明,辽宁东北林蛙种群间已经出现一定程度的遗传分化,分析认为,自然屏障(高山和平原等)以及栖息地片段化是其遗传分化形成的主要因素.