Amphipols: polymeric surfactants for membrane biology research

Membrane proteins classically are handled in aqueous solutions as complexes with detergents. The dissociating character of detergents, combined with the need to maintain an excess of them, frequently results in more or less rapid inactivation of the protein under study. Over the past few years, we have endeavored to develop a novel family of surfactants, dubbed amphipols (APs). APs are amphiphilic polymers that bind to the transmembrane surface of the protein in a noncovalent but, in the absence of a competing surfactant, quasi-irreversible manner. Membrane proteins complexed by APs are in their native state, stable, and they remain water-soluble in the absence of detergent or free APs. An update is presented of the current knowledge about these compounds and their demonstrated or putative uses in membrane biology.     

Redesign of the coenzyme specificity of a dehydrogenase by protein engineering

Directed mutagenesis and molecular modelling have been used to identify a set of amino-acid side chains in glutathione reductase that confer specificity for the coenzyme NADP+. Systematic replacement of these amino acids, all of which occur in a 'fingerprint' structural motif in the NADP+-binding domain, leaves the substrate specificity unchanged but converts the enzyme into one displaying a marked preference for the coenzyme NAD+.     

Growth hormone alters lymphocyte sub-populations and antibody production in dwarf rats in vivo

Female dwarf rats at different ages were treated with recombinant porcine GH or with a potent sheep anti-rat GH serum. Body weight and spleen weight increased with GH and decreased with anti-GH treatment (p<0.001). Neither GH nor anti-GH treatment resulted in a change in circulating WBCs, but GH decreased, while anti-GH increased, RBC counts (p<0.001). Similarly, GH treatment tended to decrease the ratio of CD4⁺:CD8⁺ T-cells while anti-GH increased (p<0.05) the ratio. Anti-GH treatment also enhanced the animals' ability to produce specific IgG in response to KLH injection. These results indicate that GH may have a physiological role in suppressing humoral immune function but may enhance cell-mediated immunity.     

Inhibited hormonal induction of hepatic phosphoenolpyruvate carboxykinase in poly I∶C treated mice,an endotoxin-like glucocorticoid antagonism

Summary Corticosteroid induction of mouse hepatic phosphoenolpyruvate carboxykinase was inhibited by prior injection of poly IC. Mice challenged with a lethal dose of endotoxin 4 h after administration of poly IC could not be protected by a concurrent injection of hydrocortisone.This investigation was supported by U. S. Public Health Service research grant No. AI-10087 from the National Institute of Allergy and Infectious Diseases.     

Exome sequencing identifies ACSF3 as a cause of combined malonic and methylmalonic aciduria

We used exome sequencing to identify the genetic basis of combined malonic and methylmalonic aciduria (CMAMMA). We sequenced the exome of an individual with CMAMMA and followed up with sequencing of eight additional affected individuals (cases). This included one individual who was identified and diagnosed by searching an exome database. We identify mutations in ACSF3, encoding a putative methylmalonyl-CoA and malonyl-CoA synthetase as a cause of CMAMMA. We also examined a canine model of CMAMMA, which showed pathogenic mutations in a predicted ACSF3 ortholog. ACSF3 mutant alleles occur with a minor allele frequency of 0.0058 in ～1,000 control individuals, predicting a CMAMMA population incidence of ～1:30,000. ACSF3 deficiency is the first human disorder identified as caused by mutations in a gene encoding a member of the acyl-CoA synthetase family, a diverse group of evolutionarily conserved proteins, and may emerge as one of the more common human metabolic disorders.     

基于蚁群粒子群优化算法的云计算资源调度方案

通过对蚁群算法和粒子群算法分别进行改进,利用两种算法自身优势相结合的方式建立一种蚁群粒子群算法,以提高云计算资源调度效率,解决云计算中资源调度方案优化问题.实验结果表明,该算法所消耗的时间更少,效果更好.     

Entanglement-free Heisenberg-limited phase estimation

Measurement underpins all quantitative science. A key example is the measurement of optical phase, used in length metrology and many other applications. Advances in precision measurement have consistently led to important scientific discoveries. At the fundamental level, measurement precision is limited by the number N of quantum resources (such as photons) that are used. Standard measurement schemes, using each resource independently, lead to a phase uncertainty that scales as 1/square root N-known as the standard quantum limit. However, it has long been conjectured that it should be possible to achieve a precision limited only by the Heisenberg uncertainty principle, dramatically improving the scaling to 1/N (ref. 3). It is commonly thought that achieving this improvement requires the use of exotic quantum entangled states, such as the NOON state. These states are extremely difficult to generate. Measurement schemes with counted photons or ions have been performed with N < or = 6 (refs 6-15), but few have surpassed the standard quantum limit and none have shown Heisenberg-limited scaling. Here we demonstrate experimentally a Heisenberg-limited phase estimation procedure. We replace entangled input states with multiple applications of the phase shift on unentangled single-photon states. We generalize Kitaev's phase estimation algorithm using adaptive measurement theory to achieve a standard deviation scaling at the Heisenberg limit. For the largest number of resources used (N = 378), we estimate an unknown phase with a variance more than 10 dB below the standard quantum limit; achieving this variance would require more than 4,000 resources using standard interferometry. Our results represent a drastic reduction in the complexity of achieving quantum-enhanced measurement precision.     

高河菜提取物对小鼠肠推进和胃排空的影响

目的:研究高河菜提取物对小鼠消化道动力的影响.方法:采用炭末推进实验观察高河菜提取物对阿托品所致小鼠小肠推进抑制的影响;采用甲基橙胃残留率的方法观察高河菜提取物对阿托品所致小鼠胃排空抑制的影响.结果:高河菜提取物2g/kg能明显拮抗阿托品对小鼠小肠推进抑制的作用;高河菜提取物2g/kg、1g/kg和0.5g/kg均能拮抗阿托品对小鼠胃排空抑制的作用.结论:高河菜提取物对阿托品所致小鼠胃肠功能障碍有明显的改善作用.