大豆磷脂中磷脂酰胆碱的分离工艺研究

大豆磷脂中含有１９％－２５％的磷脂酞胆碱,本文研究了从大豆粗磷脂中磷脂酰胆碱的分离工艺,得到了最佳的分离工艺参数。     

数字信号处理中的模拟信号恢复及其计算机实现

数字信号通过一个理想低通滤波器,即可恢复到模拟信号．从时域分析,这一过程实际上是由无限多离散点与一个进行单位平移的内插函数相乘求和的过程．本文介绍利用内插函数恢复模拟信号,以及用插补原理将数字信号对应模拟信号的图形曲线在计算机上显示的方法     

基于负载均衡的任务调度算法

基于传统任务调度算法, 通过在调度过程中增设服务器最佳期望序列及负载均衡指数, 采用任务连接数约束服务器选择, 解决了传统任务调度算法对于集群负载均衡性能的忽略问题. 实验结果表明, 该改进算法能达到较高负载均衡度, 同时缩短任务完成时间, 并提高了集群对于批量级任务的处理能力, 从而达到了优化的目的.     

The structural basis for autonomous dimerization of the pre-T-cell antigen receptor

The pre-T-cell antigen receptor (pre-TCR), expressed by immature thymocytes, has a pivotal role in early T-cell development, including TCR β-selection, survival and proliferation of CD4(-)CD8(-) double-negative thymocytes, and subsequent αβ T-cell lineage differentiation. Whereas αβTCR ligation by the peptide-loaded major histocompatibility complex initiates T-cell signalling, pre-TCR-induced signalling occurs by means of a ligand-independent dimerization event. The pre-TCR comprises an invariant α-chain (pre-Tα) that pairs with any TCR β-chain (TCRβ) following successful TCR β-gene rearrangement. Here we provide the basis of pre-Tα-TCRβ assembly and pre-TCR dimerization. The pre-Tα chain comprised a single immunoglobulin-like domain that is structurally distinct from the constant (C) domain of the TCR α-chain; nevertheless, the mode of association between pre-Tα and TCRβ mirrored that mediated by the Cα-Cβ domains of the αβTCR. The pre-TCR had a propensity to dimerize in solution, and the molecular envelope of the pre-TCR dimer correlated well with the observed head-to-tail pre-TCR dimer. This mode of pre-TCR dimerization enabled the pre-Tα domain to interact with the variable (V) β domain through residues that are highly conserved across the Vβ and joining (J) β gene families, thus mimicking the interactions at the core of the αβTCR's Vα-Vβ interface. Disruption of this pre-Tα-Vβ dimer interface abrogated pre-TCR dimerization in solution and impaired pre-TCR expression on the cell surface. Accordingly, we provide a mechanism of pre-TCR self-association that allows the pre-Tα chain to simultaneously 'sample' the correct folding of both the V and C domains of any TCR β-chain, regardless of its ultimate specificity, which represents a critical checkpoint in T-cell development. This unusual dual-chaperone-like sensing function of pre-Tα represents a unique mechanism in nature whereby developmental quality control regulates the expression and signalling of an integral membrane receptor complex.     

Effect of CO2 enrichment on the glucosinolate contents under different nitrogen levels in bolting stem of Chinese kale (Brassica alboglabra L.)

The effects of CO₂ enrichment on the growth and glucosinolate (GS) concentrations in the bolting stem of Chinese kale (Brassica alboglabra L.) treated with three nitrogen (N) concentrations (5, 10, and 20 mmol/L) were investigated. Height, stem thickness, and dry weights of the total aerial parts, bolting stems, and roots, as well as the root to shoot ratio, significantly increased as CO₂ concentration was elevated from 350 to 800 μl/L at each N concentration. In the edible part of the bolting stem, 11 individual GSs were identified, including 7 aliphatic and 4 indolyl GSs. GS concentration was affected by the elevated CO₂ concentration, N concentration, and CO₂×N interaction. At 5 and 10 mmol N/L, the concentrations of aliphatic GSs and total GSs significantly increased, whereas those of indolyl GSs were not affected, by elevated atmospheric CO₂. However, at 20 mmol N/L, elevated CO₂ had no significant effects on the concentrations of total GSs and total indolyl GSs, but the concentrations of total aliphatic GSs significantly increased. Moreover, the bolting stem carbon (C) content increased, whereas the N and sulfur (S) contents decreased under elevated CO₂ concentration in the three N treatments, resulting in changes in the C/N and N/S ratios. Also the C/N ratio is not a reliable predictor of change of GS concentration, while the changes in N and S contents and the N/S ratio at the elevated CO₂ concentration may influence the GS concentration in Chinese kale bolting stems. The results demonstrate that high nitrogen supply is beneficial for the growth of Chinese kale, but not for the GS concentration in bolting stems, under elevated CO₂ condition.     

Function of resveratrol derived from transgenic plant expressing resveratrol synthase gene

Two genes from grapevine coding for resveratrol synthase, named RS1 and RS2, were cloned by RT-PCR. AnEscherichia coli expression vector was constructed by insertion of RS1 into pBV221. A specific protein with the same molecular weight (42 ku) as the resveratrol synthase was expressed and used to prepare the rabbit antiserum. A plant expression vector was constructed by inserting the RS1 gene into pBin438 downstream of the doubled CaMV 35S promoter and TMV-Ω fragment. PCR-positive transgenic tobacco plants were obtained after transformation withAgrobacterium tumefaciens LBA4404 harboring the plant expression vector. Southern blot analysis demonstrated that the foreign gene was integrated into the tobacco genome. The results of RT-PCR and Western blot indicated that the RS1 gene was transcribed and expressed. Formation of resveratrol in transgenic tobacco was further determined by thin-layer chromatography of silica gel and HPLC. Increased accumulation of human breast adenocarcinoma cells in G₀ and G₁ phases of cell cycle was observed in cells treated with resveratrol purified from transgenic tobacco as compared to the untreated cells.     

机械能流密度矢量

本文通过对连续媒质内机械能流转移的分析,引入机械能流密度矢量S,并讨论了机械能流在动力学系统中的一些应用。     

珍稀濒危药材蛇足石杉的研究概况及开发前景

蛇足石杉中有较高含量的石杉碱甲,对治疗老年痴呆症和提高记忆力有显著疗效,备受国内外学者们的关注.系统总结了近年来国内外学者对蛇足石杉的相关研究成果,旨在为蛇足石杉资源保护与可持续利用、开展蛇足石杉繁殖技术的研究,为解决蛇足石杉原料生产的瓶颈提供理论依据.     

目标识别的灰色工程方法研究

灰色系统理论是研究贫信息系统分析、建模、预测、决策、控制的有效工具,在工程技术、社会、经济等领域应用广泛.探讨了灰色系统理论在目标识别中的应用问题,提出了目标识别的灰色关联算法、灰色统计算法、灰色聚类算法及灰色统计聚类算法.     

聚丙烯酰胺的光敏引发法制备及其在洗煤废水中的应用特性

采用紫外光照射下光敏引发聚合技术,以丙烯酰胺(AM)为单体,以水溶性光敏剂和氧化还原引发剂组成复合引发剂合成聚丙烯酰胺,并对光敏引发法合成的阴离子聚丙烯酰胺(PAPAM)和非离子聚丙烯酰胺(PNPAM)与热化学法合成的阴离子聚丙烯酰胺(TAPAM)在煤泥水中进行絮凝性能比较.结果表明,在相同条件下光敏引发合成的PAPAM用于洗煤水的絮凝沉淀净化过程中,絮凝剂用量少,沉降速度快,被处理后水的浊度低.絮凝性能明显优于热化学法所得的TAPAM,光聚法非离子聚丙烯酰胺PNPAM效果最差.该结果为洗煤水的净化处理及絮凝剂选型提供了良好的实验依据.