Petracchi D, Cercignani G, Lucia S
Istituto di Biofisica del CNR, Pisa, Italy.
Biophys J. 1996 Jan;70(1):111-20. doi: 10.1016/S0006-3495(96)79553-X.
The general modeling of dose-response curves to very low stimuli in a photosensory-effector system is critically reshaped starting from basic assumptions on the fluctuations of chemical signals inside the receptor cell, which add to those of the stimulus itself, both arising from their granular (or quantal) structure. We have shown, both through the analytical treatment of a simple kinetic scheme and by means of Monte Carlo simulations of the same, that shot noise arising from chemical transduction ("chemical shot noise") contributes considerably to the output noise of the receptor-effector system, thus affecting both the shape and the abscissa shift of dose-response curves under these conditions; the latter phenomenon has indeed been reported in Halobacterium halobium. After evaluating the general properties of a single-step amplifying mechanism, the effects of introducing several low-amplifying steps in cascade were investigated briefly. The results obtained were qualitatively and quantitatively at variance from those of earlier models on the same phenomenon, and the discrepancies are discussed in order to highlight the fundamental contribution of chemical shot noise to the response of any kind of sensory system to very low stimuli.
从受体细胞内化学信号波动的基本假设出发，对光感受效应系统中极低刺激的剂量 - 反应曲线进行的一般建模被彻底重塑，这些化学信号波动与刺激本身的波动相加，两者均源于其颗粒状（或量子化）结构。我们通过对一个简单动力学方案的分析处理以及对其进行蒙特卡罗模拟都表明，化学转导产生的散粒噪声（“化学散粒噪声”）对受体 - 效应系统的输出噪声有相当大的贡献，从而在这些条件下影响剂量 - 反应曲线的形状和横坐标偏移；后者现象确实已在嗜盐栖热菌中被报道。在评估了单步放大机制的一般特性后，简要研究了级联引入几个低放大步骤的影响。所获得的结果在定性和定量上与早期关于同一现象的模型结果不同，并且对这些差异进行了讨论，以突出化学散粒噪声对任何类型的感觉系统对极低刺激的反应的基本贡献。
