Understanding the role of nonequilibrium driving in self-organization is crucial for developing a predictive description of biological systems, yet it is impeded by their complexity. The actin cytoskeleton serves as a paradigm for how equilibrium and nonequilibrium forces combine to give rise to self-organization. Motivated by recent experiments that show that actin filament growth rates can tune the morphology of a growing actin bundle cross-linked by two competing types of actin-binding proteins [S. L. Freedman et al., Proc. Natl. Acad. Sci. U.S.A. 116, 16192–16197 (2019)], we construct a minimal model for such a system and show that the dynamics of a growing actin bundle are subject to a set of thermodynamic constraints that relate its nonequilibrium driving, morphology, and molecular fluxes. The thermodynamic constraints reveal the importance of correlations between these molecular fluxes and offer a route to estimating microscopic driving forces from microscopy experiments.

了解非平衡驱动在自组织中的作用对于开发对生物系统的预测性描述至关重要，但由于其复杂性而受到阻碍。肌动蛋白细胞骨架作为平衡和非平衡力如何结合以产生自组织的范例。最近的实验表明，肌动蛋白丝的生长速率可以调节由两种竞争类型的肌动蛋白结合蛋白交联的生长肌动蛋白束的形态[SL Freedman等人。,过程。国家石油公司。学院派。科学。美国116, 16192–16197 (2019)]，我们为这样的系统构建了一个最小模型，并表明生长肌动蛋白束的动力学受到一组与其非平衡驱动、形态和分子通量相关的热力学约束。热力学约束揭示了这些分子通量之间相关性的重要性，并提供了从显微镜实验中估计微观驱动力的途径。