Transmembrane movements of lipids

Summary Membranes allow the rapid passage of uncharged lipids. Phospholipids on the other hand diffuse very slowly from one monolayer to another with a half-time of several hours. This slow spontaneous movement in a pure lipid bilayer can be selectively modulated in biological membranes by intrinsic proteins. In microsomes, and probably in bacterial membranes, non-specific phospholipid flippases allow the rapid redistribution of newly synthesized phospholipids. In eukaryotic plasma membranes, aminophospholipid translocase selectively pumps phosphatidylserine (PS) and phosphatidylethanolamine (PE) from the outer to the inner leaflet and establishes a permanent lipid asymmetry. The discovery of an aminophospholipid translocase in chromaffin granules proves that eukaryotic organelles may also contain lipid translocators.     

Competition for antigen presentation in living cells involves exchange of peptides bound by class II MHC molecules

T cells recognize foreign proteins as peptides bound to self molecules encoded by the major histocompatibility complex (MHC). The kinetics of interaction between purified class II MHC molecules and peptides is unusual, in that the rate of association is very slow, but once formed, the complexes are extremely stable. This raises the question of how the antigen-presenting cell provides a sufficient number of free MHC binding sites to ensure T cell immunity. We present results suggesting that an exchange of peptide in MHC binding sites may take place under physiological conditions.     

Esterases of the flounder (Platichthys flesus,Pleuronectidae, Teleostei): Development of an identification protocol using starch gel electrophoresis and characterization of loci

Summary Fish esterases are among the most difficult enzymes to identify using starch gel electrophoresis because of the many loci that are simultaneously active, and especially because of duplication phenomena, satellite bands, and stain trails. In an attempt to simplify and clarify electropherograms, various staining and inhibitory methods were tested on esterases from the flounderPlatichthys flesus. A range of migration and staining buffers and substrates were used, as well as chemical inhibition and heat inactivation. A combination of the methods made it possible to distinguish and characterize the five presumed esterase loci.     

收录机装配流水线的工作研究

本文以收录机装配流水线工作研究为例，讨论了工作研究在流水线上应用的步 骤和方法。在基本不增加投资情况下，通过工作研究使流水线效率从４２．７ ％提高到 　８３．７８％，日产量由原来的１０２台提高到２０４台。本方法可以在其他流水线上普遍推 广应用。     

1969~2010年青藏高原北麓河盆地热喀斯特湖塘演化过程（英文）

基于青藏高原北麓河盆地1969年航片资料以及2003年和2010年SPOT-5遥感资料的解译,对该地区过去40年面积大于0.1 ha(1 ha=10000 m2)的热喀斯特湖面积和数量变化进行了研究.结果表明,该区域热喀斯特湖在1969~2010年间呈现显著的扩张趋势,湖塘的总数量增加了534个,总面积增加了410 ha.此外,通过对1969年所有湖塘的追踪统计,自1969~2010年大部分(84%)湖塘的面积呈增大的趋势,只有8%的湖塘面积减小和6%的湖塘彻底消失.这种湖塘数量和面积的增大趋势可能与持续升高的气温和逐渐增大的P-E值(降水与潜蒸散的差值)有关,但是一些非气候因素(如工程活动、湖底的透水性等)对湖塘的演化过程也具有重要的影响.