In lipid monolayers with phase coexistence, domains of the liquid-condensed phase always present size polydispersity. However, very few theoretical works consider size distribution effects on the monolayer properties. Because of the difference in surface densities, domains have excess dipolar density with respect to the surrounding liquid expanded phase, originating a dipolar inter-domain interaction. This interaction depends on the domain area, and hence the presence of a domain size distribution is associated with interaction polydispersity. Inter-domain interactions are fundamental to understanding the structure and dynamics of the monolayer. For this reason, it is expected that polydispersity significantly alters monolayer properties. By means of Brownian dynamics simulations, we study the radial distribution function (RDF), the average mean square displacement and the average time-dependent self-diffusion coefficient, D(t), of lipid monolayers with normally distributed size domains. For this purpose, we vary the relevant system parameters, polydispersity and interaction strength, within a range of experimental interest. We also analyze the consequences of using a monodisperse model to determine the interaction strength from an experimental RDF. We find that polydispersity strongly affects the value of the interaction strength, which is greatly underestimated if polydispersity is not considered. However, within a certain range of parameters, the RDF obtained from a polydisperse model can be well approximated by that of a monodisperse model, by suitably fitting the interaction strength, even for 40% polydispersities. For small interaction strengths or small polydispersities, the polydisperse systems obtained from fitting the experimental RDF have an average mean square displacement and D(t) in good agreement with that of the monodisperse system.

中文翻译：

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域大小的多分散性对具有相共存的脂质单分子层的结构和动力学性质的影响†

在具有相共存的脂质单分子层中，液体凝结相的域始终呈现大小多分散性。但是，很少有理论著作考虑尺寸分布对单层性能的影响。由于表面密度的差异，相对于周围的液体膨胀相，畴具有过量的偶极密度，从而引起偶极域间相互作用。这种相互作用取决于畴的面积，因此畴尺寸分布的存在与相互作用的多分散性有关。域间相互作用是理解单层结构和动力学的基础。因此，可以预期多分散性会显着改变单层性能。通过布朗动力学模拟，我们研究了径向分布函数（RDF），d（吨）的脂质单分子层具有正常分布的大小域。为此，我们在实验范围内改变了相关的系统参数，多分散性和相互作用强度。我们还分析了使用单分散模型从实验RDF确定相互作用强度的后果。我们发现多分散性强烈影响相互作用强度的值，如果不考虑多分散性，这将大大低估。但是，在一定的参数范围内，即使对于40％的多分散度，通过适当地拟合相互作用强度，也可以通过单分散模型很好地近似由多分散模型获得的RDF。对于较小的相互作用强度或较小的多分散性，D（t）与单分散体系的D（t）高度吻合。