This CAREER award supports theoretical and computational research, and education on supermolecular assemblies of nanoscale filaments. Biofilaments present inherent challenges to theoretical study owing to the flexibility of the filaments themselves and the complexity of interactions among them. These effects are governed by long-wavelength physics, representing both soft deformations along filaments, as well as collective effects of inter-filament packing geometry. The PI will investigate the statistical and thermodynamic properties of filamentous assemblies that derive from the common structure of biological filaments. Namely, biofilaments are universally long, flexible and helical. The research addresses three aims: 1) establish the role of chirally-induced topological defects in finite-diameter bundle formation; 2) build a statistical theory of protein-mediated bundling of filamentous actin; and 3) explore the statistical mechanics of crystallization of pure and inhomogeneous filament assemblies. Project (1): The PI will establish a fundamental consequence of the geometric frustration between two dimensional and chirally ordered materials in the context of dense biofilament bundles. The PI will focus on the role played by disclinations that screen long-range stresses, which are themselves induced by chiral interactions between neighboring filaments. The PI aims to illuminate the influence of chirality on molecular assembly and provide insight into assembly mechanisms of biological filaments that are inherently limited in size. Project (2): The PI aims to construct a statistical mechanical framework, a coupled lattice-gas and lattice spin model, to explore the assembly thermodynamics of parallel actin bundles. The goal is to determine how an intrinsic frustration between the respective helical and six-fold symmetries of f-actin and bundle assemblies gives rise to cooperative binding of cross-linking proteins and influences bundle formation. Project (3): The PI will investigate the critical properties of filamentous systems as they pass through an unusually complex phase transition from two dimensional liquid-crystals to true three dimensional solids. The PI further aims to assess the role of quenched impurities inherent to crystallization of polydisperse filaments and expand our knowledge of the role of disorder in soft materials. The education component supports an effort to develop a new educational program that leverages existing center and faculty resources to create a Soft Matter Research in Theory summer program for undergraduate students. The program is designed to enhance the skills of students and enable them to participate in ongoing theoretical research projects. This program introduces students to the methods and challenges of modeling soft materials and the excitement of research in this area.
NONTECHNICAL SUMMARY This CAREER award supports theoretical and computational research, and education on assemblies of filaments composed of large molecules that have dimensions on scale of a nanometer ? a billionth of a meter. Filamentous assemblies like these are found inside biological cells and play an important role in giving them structural integrity. This award supports research to understand how filamentous assemblies organize themselves into more complex structures. This has important consequences for the structural and mechanical properties of filamentous assemblies. Aspects of the research will be done in collaboration with experimental efforts that use x-rays to study filament bundling in cells. The PI seeks to uncover fundamental principles that will also apply to the design of new synthetic materials that are structured on the nanometer scale.
This research is an example of fundamental research in the mathematical and physical sciences at the boundaries with biology which has the potential to advance both.
The education component supports an effort to develop a new educational program that leverages existing center and faculty resources to create a Soft Matter Research in Theory summer program for undergraduate students. The program is designed to enhance the skills of students and enable them to participate in ongoing theoretical research projects. This program introduces students to the methods and challenges of modeling soft materials and the excitement of research in this area.
