Cell membranes mainly consist of lipid bilayers with an actively regulated composition. The underlying processes are still poorly understood, in particular, how the hundreds of components are controlled. Cholesterol has been found to correlate with phospholipid saturation for reasons that remain unclear. To better understand the link between cell membrane regulation and chemical composition, we establish a computational framework based on chemical reaction networks, resulting in multiple semigrand canonical ensembles. By running computer simulations, we show that regulating the chemical potential of lipid species is sufficient to reproduce the experimentally observed increase in acyl tail saturation with added cholesterol. Our model proposes a different picture of lipid regulation in which components can be regulated passively instead of actively. In this picture, phospholipid acyl tail composition naturally adapts to added molecules such as cholesterol or proteins. A comparison between regulated membranes with commonly studied ternary model membranes shows stark differences: for instance, correlation lengths and viscosities observed are independent of lipid chemical affinity.

中文翻译：

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调节脂质成分使变温动物的酰基尾饱和稳态合理化

细胞膜主要由具有主动调节成分的脂质双层组成。底层过程仍然知之甚少，特别是如何控制数百个组件。已发现胆固醇与磷脂饱和度相关，原因尚不清楚。为了更好地理解细胞膜调控与化学成分之间的联系，我们建立了一个基于化学反应网络的计算框架，从而产生了多个半正态集合。通过运行计算机模拟，我们表明调节脂质种类的化学势足以重现实验观察到的添加胆固醇后酰基尾饱和度的增加。我们的模型提出了一种不同的脂质调节图，其中成分可以被动调节而不是主动调节。在这张图片中，磷脂酰基尾部组成自然地适应添加的分子，如胆固醇或蛋白质。调节膜与通常研究的三元模型膜之间的比较显示出明显的差异：例如，观察到的相关长度和粘度与脂质化学亲和力无关。