Investigation of the pyrolysis products of methionine-enkephalin-Arg-Gly-Leu using liquid chromatography-tandem mass spectrometry

Low-temperature pyrolysis of methionine-enkephalin-Arg-Gly-Leu has been carried out and the non-volatile residues have been analyzed. The fragments were separated and characterized by LC-UV/Vis-MS/MS. Two major types of pyrolysis products were identified by matching the experimental results with a theoretical list that contains the expected fragments. These products were mainly composed of cyclic oligopeptides and linear fragments produced from the peptide backbone. These fragments have preserved the sequence of amino acids in the peptide. In some cases, a complete or partial loss of an amino-acid side group was observed. Tandem mass spectrometry and cyanogen bromide cleavage experiments were used to confirm the nature of the cyclic and linear pyrolysates, in addition to chromatographic and mass spectrometric data of actual standard synthetic cyclic peptides.     

Mass spectrometry of fluorocarbon‐labeled glycosphingolipids

A method for generation of novel fluorocarbon derivatives of glycosphingolipids (GSLs) with high affinity for fluorocarbon phases has been developed, and their potential applications to mass spectrometry (MS)‐based methodologies for glycosphingolipidomics have been investigated. Sphingolipid ceramide N‐deacylase (SCDase) is used to remove the fatty acid from the ceramide moiety, after which a fluorocarbon‐rich substituent (F‐Tag) is incorporated at the free amine of the sphingoid. In initial trials, a neutral GSL, globotriaosylceramide (Gb₃Cer), three purified bovine brain gangliosides, and four fungal glycosylinositol phosphorylceramides (GIPCs) were de‐N‐acylated, derivatized by prototype F‐Tags, and recovered by solid phase extraction on fluorocarbon‐derivatized silica (F‐SPE). The efficacy of SCDase treatment of GIPCs was here demonstrated for the first time. Compatibility with subsequent per‐N,O‐methylation was established for the F‐tagged Gb₃ Cer and purified gangliosides, and extensive mass spectra (MS¹ and MS²) consistent with all of the expected products were acquired. The potential use of F‐tagged derivatives for a comprehensive MS based profiling application was then demonstrated on a crude ganglioside mixture extracted from bovine brain. Finally, a simple trial in microarray format demonstrated fixation of F‐tagged G_M1 ganglioside to a fluorous glass surface, with the glycan intact and available for interaction with a fluorescent derivative of cholera toxin B chain. The methods described thus provide a new avenue for rapid GSL recovery or cleanup, potentially compatible with a variety of platforms for mass spectrometric profiling and structure analysis, as well as parallel analysis of functional interactions. Copyright © 2010 John Wiley & Sons, Ltd.     

Wavelet formulation of the polarizable continuum model

The first implementation of a wavelet discretization of the Integral Equation Formalism (IEF) for the Polarizable Continuum Model (PCM) is presented here. The method is based on the application of a general purpose wavelet solver on the cavity boundary to solve the integral equations of the IEF‐PCM problem. Wavelet methods provide attractive properties for the solution of the electrostatic problem at the cavity boundary: the system matrix is highly sparse and iterative solution schemes can be applied efficiently; the accuracy of the solver can be increased systematically and arbitrarily; for a given system, discretization error accuracy is achieved at a computational expense that scales linearly with the number of unknowns. The scaling of the computational time with the number of atoms N is formally quadratic but a N^1.5 scaling has been observed in practice. The current bottleneck is the evaluation of the potential integrals at the cavity boundary which scales linearly with the system size. To reduce this overhead, interpolation of the potential integrals on the cavity surface has been successfully used. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

AFFS技术在大尺寸LCD-TV的进展（英文）

最近我们发展了AFFS技术,做出了32″LED背光源的LCD-TV,色域达到了105%,对比度1200：1,在140°所有视角的对比度达到了100以上,我们采用双轴补偿膜大大提高了颜色漂移的特性。这些光学特性结果的取得是与工艺制作、光学材料的优化、新AFFS像素的设计分不开的。     

合成孔径成像激光雷达高分辨的一维距离像

合成孔径成像激光雷达是一种新的主动式有源成像系统,其突出优势是可以获得比合成孔径雷达更高的分辨率,和更接近光学图片的成像质量.对激光波段的高分辨距离像进行了研究,介绍了合成孔径成像激光雷达一维距离像的室内实验系统,有效地对合成孔径成像激光雷达一维距离像进行模拟.首先,简述了一维距离像的成像原理.然后,分析了系统的关键技术,给出了系统框图和连接关系,并且针对激光调谐信号的非线性问题,利用多项式推导出非线性的激光信号表达式,提出了一种时域补偿高阶相位误差的补偿方法.最后,通过实验证明了所提方法可以有效地消除各个脉冲的非线性问题,并且表明所给实验系统的可行性.     

基于狭缝摄影的靶场目标运动测量综述

狭缝摄影测量是高速摄影测量的一个重要分支,是常规武器靶场试验中,对飞行目标的各项运动与姿态参数进行记录和测量的重要方法。这里分析了狭缝摄影测量方法的特点,总结了狭缝摄影机的发展状况,深入阐述了使用狭缝摄影测量技术实现对飞行目标速度、转速、章动角等重要参数测量的基本原理,并对狭缝摄影测量的发展趋势进行了展望。     

一种无运放电流模式带隙基准设计

为满足集成电路中低功耗／低温度系数的要求,基于负反馈钳位原理,采用分段线性补偿技术,通过在高低温度段分别插入非线性电流修正项对基准进行了曲率补偿,得到一种新型的无需运放的曲率补偿电流模式带隙电压基准源。仿真得到典型工艺下电路在室温27℃,工作电压4．5V下输出电压1．25062V,工作电流小于38pA,功耗小于170μW。在-40～＋150℃。宽温度范围内,基准电压在1．25018～1．25086V之间变化,温度系数约为2．86ppm／℃。     

煤矿矿井数学模型的研究

通过各监测点处瓦斯浓度,风速等观测值来判定其高低瓦斯矿井,详细阐述了煤矿瓦斯绝对、相对浓度的计算方法;通过瓦斯煤尘的检测数据,对矿井发生爆炸的概率进行建模预测,估算出了该矿井的不安全程度。在数据处理过程中主要借助Excel、Matlab等辅助工具来实现。此外还根据《煤矿安全规程》对主要工作面风量进行了规划,得出了最优通风模型;具有较强参考价值。