Bezrukov Sergey M., Vodyanoy Igor
Laboratory of Physical and Structural Biology, NICHD, National Institutes of Health, Bethesda, Maryland 20892-0924St. Petersburg Nuclear Physics Institute, Gatchina, Russia 188350.
Chaos. 1998 Sep;8(3):557-566. doi: 10.1063/1.166337.
At the molecular level many thermally activated reactions can be viewed as Poisson trains of events whose instantaneous rates are defined by the reaction activation barrier height and an effective collision frequency. When the barrier height depends on an external parameter, variation in this parameter induces variation in the event rate. Extending our previous work, we offer a detailed theoretical analysis of signal transduction properties of these reactions considering the external parameter as an input signal and the train of resulting events as an output signal. The addition of noise to the system input facilitates signal transduction in two ways. First, for a linear relationship between the barrier height and the external parameter the output signal power grows exponentially with the mean square fluctuation of the noise. Second, for noise of a sufficiently high bandwidth, its addition increases output signal quality measured as the signal-to-noise ratio (SNR). The output SNR reaches a maximum at optimal noise intensity defined by the reaction sensitivity to the external parameter, reaction initial rate, and the noise bandwidth. We apply this theory to ion channels of excitable biological membranes. Based on classical results of Hodgkin and Huxley we show that open/closed transitions of voltage-gated ion channels can be treated as thermally activated reactions whose activation barriers change linearly with applied transmembrane voltage. As an experimental example we discuss our recent results obtained with polypeptide alamethicin incorporated into planar lipid bilayers.(c) 1998 American Institute of Physics.
在分子层面，许多热激活反应可被视为事件的泊松序列，其瞬时速率由反应活化能垒高度和有效碰撞频率决定。当能垒高度依赖于一个外部参数时，该参数的变化会导致事件发生率的变化。在我们之前工作的基础上，我们将外部参数视为输入信号，将由此产生的事件序列视为输出信号，对这些反应的信号转导特性进行了详细的理论分析。向系统输入中添加噪声以两种方式促进信号转导。首先，对于能垒高度与外部参数之间的线性关系，输出信号功率随噪声的均方涨落呈指数增长。其次，对于具有足够高带宽的噪声，添加噪声会提高以信噪比（SNR）衡量的输出信号质量。输出信噪比在由反应对外部参数的灵敏度、反应初始速率和噪声带宽所定义的最佳噪声强度下达到最大值。我们将这一理论应用于可兴奋生物膜的离子通道。基于霍奇金和赫胥黎的经典结果，我们表明电压门控离子通道的开放/关闭转变可被视为热激活反应，其活化能垒随施加的跨膜电压线性变化。作为一个实验示例，我们讨论了我们最近将多肽短杆菌肽掺入平面脂质双层所获得的结果。(c) 1998美国物理研究所。
