Dipartimento di Scienze della Salute, Università degli Studi di Milano - Bicocca, Via Cadore 48, 20900 Monza (MB), Italy.
J Chem Phys. 2013 Nov 14;139(18):184102. doi: 10.1063/1.4829146.
The mass-action law, which predicts the rates of chemical reactions, is widely used for modeling the kinetics of the chemical reactions and their stationary states, also for complex chemical reaction networks. However, violations of the mass-action equations have been reported in various cases: in confined systems with a small number of molecules, in non-ideally-stirred systems, when the reactions are limited by the diffusion, at high concentrations of reactants, or in chemical reaction networks with marginally stable mass-action equations. In this paper, I describe a new mechanism, leading to the violation of the mass-action equations, that takes place at a low concentration of at least one of the reactants; in this limit, the reaction rates can be easily inferred from the chemical reaction network. I propose that this mechanism underlies the replication stability of the hypercycles, a class of chemical reaction networks hypothetically connected with abiogenesis. I provide two simple examples of chemical reaction networks in which the mechanism leading to the violation of the mass-action law is present. I study the two chemical reaction networks by means of a simulation performed with a cellular automaton model. The results have a general validity and represent a limitation of the validity of the mass-action law, which has been overlooked up to now in the studies about the chemical reaction networks.
质量作用定律广泛用于预测化学反应速率，用于模拟化学反应的动力学及其稳定态，也用于复杂的化学反应网络。然而，在各种情况下都报道了违反质量作用方程的情况：在分子数量较少的受限系统中、在非理想搅拌系统中、当反应受到扩散限制时、在反应物浓度较高时，或者在质量作用方程具有临界稳定性的化学反应网络中。在本文中，我描述了一种新的机制，即在至少一种反应物的低浓度下发生，导致违反质量作用方程；在这种极限下，反应速率可以很容易地从化学反应网络中推断出来。我提出这种机制是超循环复制稳定性的基础，超循环是一类与生物起源假设相关的化学反应网络。我提供了两个简单的化学反应网络的例子，其中存在导致违反质量作用定律的机制。我使用元胞自动机模型进行模拟来研究这两个化学反应网络。结果具有普遍的有效性，代表了迄今为止在化学反应网络研究中被忽视的质量作用定律的有效性限制。
