期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：50
页码：15308-15313
DOI：10.1073/pnas.1513210112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceRecent experiments show that the rotational diffusion of proteins and patchy colloids does not always follow the Stokes-Einstein relation, especially in crowded environments or with the use of external fields. Because cellular cytoplasm is very crowded, this finding can have consequences for protein complex formation such as viruses. We study the kinetic network of simple models for proteins and patchy colloids and find that their dynamical self-assembly pathways change with varying the rotational diffusion constant. In particular, lowering the rotational diffusion avoids frustrated intermediate states. Such control of kinetic networks would also benefit the design of new self-assembled functional materials. Predicting the self-assembly kinetics of particles with anisotropic interactions, such as colloidal patchy particles or proteins with multiple binding sites, is important for the design of novel high-tech materials, as well as for understanding biological systems, e.g., viruses or regulatory networks. Often stochastic in nature, such self-assembly processes are fundamentally governed by rotational and translational diffusion. Whereas the rotational diffusion constant of particles is usually considered to be coupled to the translational diffusion via the Stokes-Einstein relation, in the past decade it has become clear that they can be independently altered by molecular crowding agents or via external fields. Because virus capsids naturally assemble in crowded environments such as the cell cytoplasm but also in aqueous solution in vitro, it is important to investigate how varying the rotational diffusion with respect to transitional diffusion alters the kinetic pathways of self-assembly. Kinetic trapping in malformed or intermediate structures often impedes a direct simulation approach of a kinetic network by dramatically slowing down the relaxation to the designed ground state. However, using recently developed path-sampling techniques, we can sample and analyze the entire self-assembly kinetic network of simple patchy particle systems. For assembly of a designed cluster of patchy particles we find that changing the rotational diffusion does not change the equilibrium constants, but significantly affects the dynamical pathways, and enhances (suppresses) the overall relaxation process and the yield of the target structure, by avoiding (encountering) frustrated states. Besides insight, this finding provides a design principle for improved control of nanoparticle self-assembly.
