Zinc binding to peptide analogs of the structural zinc site in alcohol dehydrogenase: Implications for an entatic state

Zinc binding to the peptide replica and analogs to residues 93–115 of horse liver alcohol dehydrogenase (ADH) was examined by competition of the peptides and the chromophoric chelator 4-(2- pyridylazo)resorcinol for zinc and X-ray absorption fine structure analysis of the zinc ligands. In the enzyme, zinc is coordinated by four Cys residues. In the peptide replica, zinc is bound to three Cys and one His residue. A four-Cys zinc coordination is observed only when His is removed, leading to increased zinc stability. ADH crystal structures reveal that the ε-amino group of the conserved residue Lys323 is within H-bond distance of the backbone amide oxygens of residues 103, 105 and 108, likely stabilizing the zinc coordination in the enzyme. The peptide data thus indicate structural strain and increased energy in the zinc-binding site in the protein, characteristic of an entatic state, implying a functional nature for this zinc site. Received 3 July 2008; received after revision 11 August 2008; accepted 1 September 2008     

动态投入产出系统消费跟踪的优化生产策略

对动态投入产出系统消费跟踪模型,按实际消费要求进行了修正,同时引入了生产过程优化目标函数,提出了动态投入产出生产策略的优化问题,进而得出了求解方法并给出了优化的生产结构调整策略．     

模糊数学在高等级公路路面选型中的应用

应用模糊数学的多层次综合评判法对路面选型问题进行了研究,提出了路面选型的评价体系,并应用专家评分法确定了各因素的权重,可根据综合评价值选用较优的路面类型．     

一种时变滑模平面的设计方法

在分析滑模平面设计的基础上,指出了按传统的方法设计的滑模平面的缺陷。为了克服此缺陷,根据矩阵分析理论提出了一种新的具有全局鲁棒性的时变滑模平面的设计方法,并给出了三种具体的滑模平面形式。通过理论分析和计算机仿真可以看出,基于该方法设计出滑模平面的变结构控制系统,能保证系统从任意的初始状态开始就处于设定的滑模平面上,对参数摄动和外部干扰具有很强的鲁棒性。用该方法设计出的时变滑模平面是传统的滑模平面的     

Betaine homocysteine S-methyltransferase: just a regulator of homocysteine metabolism?

Betaine homocysteine methyltransferase (BHMT), a Zn²⁺-dependent thiolmethyltransferase, contributes to the regulation of homocysteine levels, increases in which are considered a risk factor for cardiovascular diseases. Most plasma homocysteine is generated through the liver methionine cycle, in which BHMT metabolizes approximately 25% of this non-protein amino acid. This process allows recovery of one of the three methylation equivalents used in phosphatidylcholine synthesis through transmethylation, a major homocysteine-producing pathway. Although BHMT has been known for over 40 years, the difficulties encountered in its isolation precluded detailed studies until very recently. Thus, the last 10 years, since the sequence became available, have yielded extensive structural and functional data. Moreover, recent findings offer clues for potential new functions for BHMT. The purpose of this review is to provide an integrated view of the knowledge available on BHMT, and to analyze its putative roles in other processes through interactions uncover to date. Received 26 May 2006; received after revision 3 July 2006; accepted 24 August 2006     

Structural characterization of two papaya chitinases, a family GH19 of glycosyl hydrolases

Two chitinases, able to use tetra-N-acetylglucosamine, chitin and chitosan as substrates, were characterized after purification from Carica papaya latex. The complete amino acid sequence of the major form and about 40% of the minor one were determined through proteolytic digestions and mass spectroscopy analysis. Sequencing demonstrated that both papaya chitinases are members of the family 19 of glycosyl hydrolases (GH19). Based on the known 3-D structures of other members of family GH19, it was expected that papaya chitinases would adopt all-alpha structures. However, circular dichroism and infrared spectroscopy indicated, for the papaya chitinases, a content of 15–20% of extended structures besides the expected 40% of alpha helices. Since the fully sequenced papaya chitinase contains a large number of proline residues the possibility that papaya chitinase contains polyproline II stretches was examined in the context of their resistance against proteolytic degradation. Received 11 July 2006; received after revision 13 October 2006; accepted 25 October 2006     

经济系统发展动力结构优化模型与评价方法

以产出型生产函数为基础构建了目标函数为人均增长速度最大的经济系统发展动力结构优化模型 ,给出了最优动力结构的特征和条件以及实际动力结构与最优动力结构之间差异程度的评价方法.     

非线性溃变理论物质结构的系统制约观

基于物质结构实在性和非线性演化模型而提出的溃变理论是非线性理论的观念性观点。本文从四个方面概括了非线性溃变理论的物质系统不同于西方第一推动体系的制约观。（１）在整体观中具体完善了事物演化的“稳定,渐变,不稳定,突变,通过不连续溃变并演化为新的稳定,渐变……”的系统整体演化链。（２）以物质结构的非均匀性提出了第二搅动下物质的涡旋结构观,揭示了“天人合一”的物质性。（３）在结构信息控制观中阐述了非均匀     

银行卡网络价格结构与刷卡消费组合决策模型

针对银行卡网络价格结构与刷卡消费之间复杂的关联问题,引入双边市场理论和组合决策思想,以实现银行卡网络整体发展为目标,基于Wright等设计的银行卡网络交换费优化模型,建立了银行卡网络价格结构与刷卡消费组合决策模型.通过加入扰动因子、采用双适应值比较和保留边界不可行解改进了粒子群算法,解决了模型的求解难题,为合理制定银行卡网络价格结构提供了一种新方法,同时拓宽了双边市场理论的应用领域,在电子支付管理领域具有广阔的应用前景.