Theoretical Studies On The Dynamic Aspects Of Macromolec

在本报告所述期间，发表了关于下列项目的论文：(1)膜通道中的颗粒数波动；(2)非平衡单分子拉动实验的自由能重建；(3)利用核磁共振弛豫数据分析大分子的缓慢结构域间运动；(4)可逆反应动力学中的长时间拖尾； (5)朗之万粒子的不可逆反应。前三个直接涉及分析实验所需的理论，重点将放在这些方面。第一个问题涉及如何分析通过膜的电流中的过量噪声，以了解代谢物的通道便利运输。第二个解决了如何利用激光镊子和原子力显微镜从单分子的微观操作中获得热力学信息这一重大悬而未决的问题。在这样的实验中，一个分子通过拉动它而被迫经历构象变化。因此，这个系统被驱离了均衡。我们展示了如何从重复作用力实验中提取平衡构象变化的能量学。第三，我们展示了如何解释核磁共振弛豫数据，以获得有关大分子缓慢的域间运动的性质的信息。本工作主要研究钙调蛋白(CaM)，它由两个由柔性螺旋连接的结构域组成。我们能够确定这两个域的相对运动的时间尺度和幅度。这在功能上很重要，因为许多信号通路都涉及到在CaM的两个结构域之间夹住一个靶肽。预计本文提出的方法将会得到广泛的应用。

In this reporting period, papers dealing with the following projects appeared in print: (1) Particle number fluctuations in a membrane channel; (2) Free energy reconstruction from non equilibrium single molecule pulling experiments; (3) Analysis of slow interdomain motion of macromolecules using NMR relaxation data; (4) Long time tails in the kinetics of reversible reactions; (5) Irreversible reactions of Langevin particles. The first three deal directly with the theory required to analyze experiments and the focus will be on these. The first deals with the problem of how to analyse the excess noise in the electric current through membranes to learn about the channel-facilated transport of metabolites. The second solves the important outstanding problem of how to obtain thermodynamic information from micromanipulation of single molecules using lazer tweezers and atomic force microscopes. In such experiments a molecule is forced to undergo conformational changes by pulling on it. Thus the system is driven away from equilibrium. We show how one can extract the energetics of equilibrium conformational changes from repeated force experiments. Thirdly, we show how NMR relaxation data should be interpreted to yield information about the nature of slow interdomain motions of macromolecules. This work focused on calmodulin(CaM) which consists of two domains connected by a flexible helical linker. We were able the determine both the timescale and amplitude of the relative motion of the two domains. This is functionally important because many signalling pathways involve the clamping of a target peptide between the two domains of CaM. It is expected that the method developped in this paper will be widely used.