Brogioli Doriano
Dipartimento di Medicina Sperimentale, Università degli Studi di Milano, Bicocca Via Cadore 48, Monza (MI) I-20052, Italy.
Phys Rev E Stat Nonlin Soft Matter Phys. 2011 Sep;84(3 Pt 1):031931. doi: 10.1103/PhysRevE.84.031931. Epub 2011 Sep 29.
Concentration fluctuations are always present in solutions; it has been noticed that, in chemical systems, they can lead to deviations from what is expected from mass-action equations. I recently described the class of the "marginally stable" chemical systems; namely, a system that have an infinity of stationary states forming a continuous curve, and I showed that they present such deviations, which appear as a drift along the stationary-state curve [Phys. Rev. Lett. 105, 058102 (2010)]. Here I describe various marginally stable chemical reaction networks, including replicating molecules, and I present numerical calculations based on reaction-diffusion master equations, showing that the thermodynamic fluctuations induce a drift. This drift can be interpreted in terms of evolution toward a more efficiently replicating system and is analogous to a Darwinian evolution. The concentration fluctuations observed during the drift are scale invariant. Relevance of this phenomenon to the origin of life is discussed. I propose that marginal stability is the mathematical property defining chemical reaction networks potentially involved in the origin of life.
浓度涨落总是存在于溶液中；人们已经注意到，在化学系统中，它们会导致与质量作用方程预期结果的偏差。我最近描述了“临界稳定”化学系统的类别；也就是说，一个具有无穷多个稳态形成连续曲线的系统，并且我表明它们会出现这种偏差，表现为沿着稳态曲线的漂移[《物理评论快报》105, 058102 (2010)]。在这里，我描述了各种临界稳定化学反应网络，包括复制分子，并给出了基于反应扩散主方程的数值计算，表明热力学涨落会引发漂移。这种漂移可以解释为朝着更高效复制系统的演化，类似于达尔文式的进化。漂移过程中观察到的浓度涨落是尺度不变的。讨论了这一现象与生命起源的相关性。我提出临界稳定性是定义可能参与生命起源的化学反应网络的数学性质。
