Enantioselective total syntheses of (−)-clavaminol A and deacetyl (+)-clavaminol H

An efficient enantioselective approach to the syntheses of (?)-clavaminol A and deacetyl (+)-clavaminol H is presented, starting from n-decanol. The synthesis features Sharpless asymmetric dihydroxylation (AD), regioselective epoxide formation/opening and α-tosylation as key steps.     

用闪光法测不良导体热导率

介绍了用闪光脉冲非稳态法测不良导体热导率的实验原理、装置及实验过程．给出了两种样品热导率的测量结果．     

A convenient microwave-assisted synthesis of cinchona alkaloid-derived ligands

An efficient synthesis of cinchona alkaloid-derived ligands based on solvent-free microwave-assisted reaction was described. The coupling of 1,4-dichlorophthalazine or 3,6-dichloropyridazine with quinine, cinchonine or cinchonidine provide bis-or monocinchona alkaloid-derived ligands in moderate to good yields （52-89%） within 15 min under optimum microwave conditions.     

Influence of the kind of the Alcoholic Modifier on Chiral Separation of 4-Substituted-Pyrrolidin-2-Ones Using Amylose Based Chiral Stationary Phase

ABSTRACT

The enantioselective separation of 4-substituted-pyrrolidin-2-ones was investigated on a silica-based amylose tris (3, 5-dimetliylphenylcarbamate) (Chiralpak AD) using, normal phase methodology with a mobile phase consisting of H-hexane-alcohol (ethanol, 1-propanol or 2-propanol) in various percentage. Effects of variation of concentration of alcohol and the nature of aliphatic alcohols in the mobile phase were studied. In a general manner, for the ten compounds analysed, the retention times increased and the separations factors were improved on changing the alcohol modifier from 2-propanol to ethanol. The effects of substitution were analysed. Baseline separation was easily obtained in many cases with a maximum resolution factor of 11.     

Assessment of applicability domain for multivariate counter-propagation artificial neural network predictive models by minimum Euclidean distance space analysis: A case study

Alongside the validation, the concept of applicability domain (AD) is probably one of the most important aspects which determine the quality as well as reliability of the established quantitative structure–activity relationship (QSAR) models. To date, a variety of approaches for AD estimation have been devised which can be applied to particular type of QSAR models and their practical utilization is extensively elaborated in the literature. The present study introduces a novel, simple, and effective distance-based method for estimation of the AD in case of developed and validated predictive counter-propagation artificial neural network (CP ANN) models through a proficient exploitation of the Euclidean distance (ED) metric in the structure-representation vector space. The performance of the method was evaluated and explained in a case study by using a pre-built and validated CP ANN model for prediction of the transport activity of the transmembrane protein bilitranslocase for a diverse set of compounds. The method was tested on two more datasets in order to confirm its performance for evaluation of the applicability domain in CP ANN models. The chemical compounds determined as potential outliers, i.e., outside of the CP ANN model AD, were confirmed in a comparative AD assessment by using the leverage approach. Moreover, the method offers a graphical depiction of the AD for fast and simple determination of the extreme points.     

Metabolism of amyloid β peptide and pathogenesis of Alzheimer’s disease

The conversion of what has been interpreted as “normal brain aging” to Alzheimer’s disease (AD) via transition states, i.e., preclinical AD and mild cognitive impairment, appears to be a continuous process caused primarily by aging-dependent accumulation of amyloid β peptide (Aβ) in the brain. This notion however gives us a hope that, by manipulating the Aβ levels in the brain, we may be able not only to prevent and cure the disease but also to partially control some very significant aspects of brain aging. Aβ is constantly produced from its precursor and immediately catabolized under normal conditions, whereas dysmetabolism of Aβ seems to lead to pathological deposition upon aging. We have focused our attention on elucidation of the unresolved mechanism of Aβ catabolism in the brain. In this review, I describe a new approach to prevent AD development by reducing Aβ burdens in aging brains through up-regulation of the catabolic mechanism involving neprilysin that can degrade both monomeric and oligomeric forms of Aβ. The strategy of combining presymptomatic diagnosis with preventive medicine seems to be the most pragmatic in both medical and socioeconomical terms.     

Coprinus comatus filtrate extract,a novel neuroprotective agent of natural origin

Abstract

In vitro acetylholinesterase (AChE) inhibitory activity of an autochthonous sample of the mushroom Coprinus comatus (encompassing fruiting body FB, mycelia M and filtrate F from the submerged cultivation) was the subject of this study. C. comatus F extract exhibited rather potent anti-AChE activity (73.0?±?1.5%) at in liquid conditions, comparable to those of the conventional drug donepezil (80.6?±?1.4%). Also, the same extract exhibited high anti-AChE activity (1?µg) in solid. While its FTIR spectrum indicated the presence of phenolic compounds, quercetin (28.1?µg g^?1 d.w.) was found to affect the observed bioactivity (59.8?±?0.9%). This is the first report of profound anti-AChE activity of any C. comatus extract, a medicinal mushroom that has been successfully cultivated in P.R. China, due to the demanding needs of food industry.     

液相色谱-质谱在阿尔茨海默病研究中的应用

液相色谱-质谱联用（LC-MS）作为集高效分离与定性定量检测为一体的联用技术,近年来在化学、医学、药学和生物化学等领域获得了长足的发展,特别是由科研领域拓展到临床诊断,开启了疾病诊断技术的新篇章。阿尔茨海默病（Alzheimer’s disease,AD）,又称老年性痴呆症,是现代社会第四大致死疾病。随着我国人口的快速老龄化,重视对AD的防治是实现健康老龄化以及国民经济持续发展的重要保障之一。本文对LC-MS的新进展进行了简介,并详细综述了近3年来其在AD研究中的应用,以期相关方法获得更好的理解与更多的关注。     

基于FPGA的自适应调节光栅光谱仪

采用FPGA作驱动和控制电路的核心,以简单的逻辑电路实现了CCD曝光时间和可编程放大器增益的自适应控制.在此基础上开发了能将信号幅度自动调节到合适范围的光栅光谱仪,采用USB总线实现系统与上位机的通讯,由LabVIEW平台开发出的应用程序进行光谱数据存储、谱图显示和处理.     

Comparative study of sub-micrometer polymeric structures: Dot-arrays, linear and crossed gratings generated by UV laser based two-beam interference, as surfaces for SPR and AFM based bio-sensing

Two-dimensional gratings are generated on poly-carbonate films spin-coated onto thin gold-silver bimetallic layers by two-beam interference method. Sub-micrometer periodic polymer dots and stripes are produced illuminating the poly-carbonate surface by p- and s-polarized beams of a frequency quadrupled Nd:YAG laser, and crossed gratings are generated by rotating the substrates between two sequential treatments. It is shown by pulsed force mode atomic force microscopy that the mean value of the adhesion is enhanced on the dot-arrays and on the crossed gratings. The grating-coupling on the two-dimensional structures results in double peaks on the angle dependent resonance curves of the surface plasmons excited by frequency doubled Nd:YAG laser. The comparison of the resonance curves proves that a surface profile ensuring minimal undirected scattering is required to optimize the grating-coupling, in addition to the minimal modulation amplitude, and to the optimal azimuthal orientation. The secondary minima are the narrowest in presence of linear gratings on multi-layers having optimized composition, and on crossed structures consisting of appropriately oriented polymer stripes. The large coupling efficiency and adhesion result in high detection sensitivity on the crossed gratings. Bio-sensing is realized by monitoring the rotated-crossed grating-coupled surface plasmon resonance curves, and detecting the chemical heterogeneity by tapping-mode atomic force microscopy. The interaction of Amyloid-β peptide, a pathogenetic factor in Alzheimer disease, with therapeutical molecules is demonstrated.