Colmenares P J
Institute of Theoretical Dynamics, University of California, Davis 95616.
J Theor Biol. 1993 Mar 21;161(2):175-98. doi: 10.1006/jtbi.1993.1049.
The electric current noise through an open channel in a membrane is analyzed with the aid of a stochastic differential equation to describe the process of ionic permeation along the channel. Unlike the Langevin theory, the effective friction constant of the channel is given by a deterministic quantity plus a multiplicative noise. The Brownian or additive noise is taken as white. Two models for the multiplicative noise are considered, a dichotomous Markov process and white noise. In both models, the correlation function decays exponentially and, therefore, the spectral density of the noise is a Lorentzian with a corner frequency proportional to the effective friction coefficient. The relaxation time of the fluctuations is modulated by the strength of the multiplicative noise. We conclude that these models characterize only those dynamical processes that occur on the rapid time scale of diffusion and cannot be used to describe slow conformational changes of a protein channel.
借助一个随机微分方程来分析通过膜中开放通道的电流噪声，以描述离子沿通道渗透的过程。与朗之万理论不同，通道的有效摩擦常数由一个确定性量加上一个乘性噪声给出。布朗噪声或加性噪声被视为白噪声。考虑了乘性噪声的两种模型，一种是二分马尔可夫过程，另一种是白噪声。在这两种模型中，相关函数都呈指数衰减，因此，噪声的谱密度是一个洛伦兹分布，其截止频率与有效摩擦系数成正比。涨落的弛豫时间由乘性噪声的强度调制。我们得出结论，这些模型仅表征在扩散的快速时间尺度上发生的那些动力学过程，不能用于描述蛋白质通道的缓慢构象变化。
