Floris Elisa, Piras Andrea, Pezzicoli Francesco Saverio, Zamparo Marco, Dall'Asta Luca, Gamba Andrea
Institute of Condensed Matter Physics and Complex Systems, Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy.
Italian Institute for Genomic Medicine and Candiolo Cancer Institute IRCCS, Strada Provinciale 142, km 3.95, Candiolo (TO) 10060, Italy.
Phys Rev E. 2022 Oct;106(4-1):044412. doi: 10.1103/PhysRevE.106.044412.
Molecular sorting is a fundamental process that allows eukaryotic cells to distill and concentrate specific chemical factors in appropriate cell membrane subregions, thus endowing them with different chemical identities and functional properties. A phenomenological theory of this molecular distillation process has recently been proposed [M. Zamparo, D. Valdembri, G. Serini, I. V. Kolokolov, V. V. Lebedev, L. Dall'Asta, and A. Gamba, Phys. Rev. Lett. 126, 088101 (2021)0031-900710.1103/PhysRevLett.126.088101], based on the idea that molecular sorting emerges from the combination of (a) phase separation driven formation of sorting domains and (b) domain-induced membrane bending, leading to the production of submicrometric lipid vesicles enriched in the sorted molecules. In this framework, a natural parameter controlling the efficiency of molecular distillation is the critical size of phase separated domains. In the experiments, sorting domains appear to fall into two classes: unproductive domains, characterized by short lifetimes and low probability of extraction, and productive domains, that evolve into vesicles that ultimately detach from the membrane system. It is tempting to link these two classes to the different fates predicted by classical phase separation theory for subcritical and supercritical phase separated domains. Here, we discuss the implication of this picture in the framework of the previously introduced phenomenological theory of molecular sorting. Several predictions of the theory are verified by numerical simulations of a lattice-gas model. Sorting is observed to be most efficient when the number of sorting domains is close to a minimum. To help in the analysis of experimental data, an operational definition of the critical size of sorting domains is proposed. Comparison with experimental results shows that the statistical properties of productive and unproductive domains inferred from experimental data are in agreement with those predicted from numerical simulations of the model, compatibly with the hypothesis that molecular sorting is driven by a phase separation process.
分子分选是一个基本过程，它使真核细胞能够在合适的细胞膜亚区域中提纯和浓缩特定化学因子，从而赋予它们不同的化学特性和功能属性。最近有人提出了一种关于这种分子蒸馏过程的唯象理论[M. 赞帕罗、D. 瓦尔登布里、G. 塞里尼、I. V. 科洛科洛夫、V. V. 列别杰夫、L. 达尔 - 阿斯塔和A. 甘巴，《物理评论快报》126, 088101 (2021)0031 - 900710.1103/PhysRevLett.126.088101]，其基于这样的观点：分子分选源于以下两者的结合：(a) 相分离驱动的分选域形成，以及 (b) 域诱导的膜弯曲，导致产生富含被分选分子的亚微米级脂质囊泡。在此框架下，控制分子蒸馏效率的一个自然参数是相分离域的临界尺寸。在实验中，分选域似乎分为两类：非生产性域，其特征是寿命短且提取概率低；以及生产性域，其会演变成最终从膜系统脱离的囊泡。人们很想将这两类与经典相分离理论对亚临界和超临界相分离域预测的不同命运联系起来。在此，我们在先前引入的分子分选唯象理论框架内讨论这种情况的含义。该理论的几个预测通过晶格气体模型的数值模拟得到了验证。当分选域的数量接近最小值时，观察到分选效率最高。为了帮助分析实验数据，提出了分选域临界尺寸的操作定义。与实验结果的比较表明，从实验数据推断出的生产性和非生产性域的统计特性与模型数值模拟预测的特性一致，这与分子分选由相分离过程驱动的假设相符。
