Wong Vance, Case David A, Szabo Attila
Department of Chemistry and Chemical Biology, and BioMaPS Institute, Rutgers University, Piscataway, NJ 08854-8087, USA.
Proc Natl Acad Sci U S A. 2009 Jul 7;106(27):11016-21. doi: 10.1073/pnas.0809994106. Epub 2009 Jun 18.
Most theoretical models for NMR relaxation in liquids assume that overall rotational motion can be described as rotational diffusion with a single diffusion tensor. Such models cannot handle motions (such as between "closed" and "open" states of an enzyme, or between conformers of a partially disordered system) where the shape of the molecule (and hence its rotational diffusion behavior) fluctuates. We provide here a formalism for dealing with such problems. The model involves jumps between discrete conformers with different overall diffusion tensors, and a master (rate) equation to describe the transitions between these conformers. Numerical examples are given for a two-site jump model where global and local motions are concerted, showing how the rate of conformational transitions (relative to the rate of rotational diffusion) affects the observed relaxation parameters.
大多数关于液体中核磁共振弛豫的理论模型都假定,整体旋转运动可以描述为具有单一扩散张量的旋转扩散。这类模型无法处理分子形状(以及由此产生的旋转扩散行为)发生波动的运动(比如酶在“闭合”和“开放”状态之间,或部分无序系统的构象异构体之间的运动)。我们在此提供一种处理此类问题的形式体系。该模型涉及具有不同整体扩散张量的离散构象异构体之间的跃迁,以及一个主(速率)方程来描述这些构象异构体之间的转变。针对全局和局部运动协同的双位点跃迁模型给出了数值示例,展示了构象转变速率(相对于旋转扩散速率)如何影响观测到的弛豫参数。