APPLICATION OF TIME-RESOLVED V-51 2D NMR FOR QUANTITATION OF KINETIC EXCHANGE PATHWAYS BETWEEN VANADATE MONOMER, DIMER, TETRAMER, AND PENTAMER
APPLICATION OF TIME-RESOLVED V-51 2D NMR FOR QUANTITATION OF KINETIC EXCHANGE PATHWAYS BETWEEN VANADATE MONOMER, DIMER, TETRAMER, AND PENTAMER
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DOI：
10.1021/ja00164a009
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发表时间：
1990-04-11
影响因子：
15
通讯作者：
THEISEN, LA
中科院分区：
文献类型：
--
作者：
CRANS, DC;RITHNER, CD;THEISEN, LA
利用二维51 V核磁共振交换实验（2D-EXSY）研究了钒酸盐在水溶液中的齐聚反应。本文介绍了在2D-EXSY实验中用51 V（I =7/2）首次定量测量复杂分子间化学交换速率。微观（伪一级）速率常数的分子间交换，通过使用数值方法来解决的2D交换矩阵。将二维交换矩阵转化为速率矩阵，可用于四种交换钒物种的动力学分析。单体形成的主要途径是二聚体的单分子分解。二聚体形成的主要途径是单体的二聚化。四聚体主要由两个单体和一个二聚体形成。在低钒酸盐浓度下，五聚体以相似的速率形成四聚体和单体或二聚体。在较高的钒酸盐浓度下，五聚体与四聚体的交换更迅速。钒酸盐单体参与比任何其他物种更重要的反应途径。钒酸盐二聚体固有地比四聚体和五聚体更不稳定，如其快速水解速率所示。我们的分析证明了一种方法，适用于解决其他多交换系统。2D-EXSY方法是通用的，可能成为确定钒在化学和生物系统中作用的主要反应途径的核心。
A two-dimensional 51V homonuclear NMR exchange experiment (2D-EXSY) has been used to study the oligomerization reactions vanadate undergoes in aqueous solutions. This manuscript describes the first quantitative measurement of complex intermolecular chemical exchange rates by using 51V (I =7/2) in a 2D-EXSY experiment. Microscopic (pseudo-first-order) rate constants for intermolecular exchange were obtained by using a numerical procedure to solve the 2D exchange matrix. The 2D exchange matrix was converted to a rate matrix that could be used in a kinetic analysis of the four exchanging vanadium species. The major pathway for monomer formation is unimolecular decomposition of the dimer. The major pathway for dimer formation is dimerization of the monomer. The tetramer forms mainly from two monomers and one dimer. At low vanadate concentrations, the pentamer forms tetramer and either monomer or dimer with similar rate. At higher vanadate concentration, the pentamer exchanged more rapidly with the tetramer. The vanadate monomer is involved in more significant reaction pathways than any other species. The vanadate dimer is inherently more labile than the tetramer and pentamer as illustrated by its rapid hydrolysis rate. Our analysis demonstrates an approach that is applicable to solving other multiexchange system. The 2D-EXSY method is versatile and may become central to determining the major reaction pathways by which vanadium acts in both chemical and biological systems.