title: Crowding in polymer-nanoparticle mixtures.
abstract: The cell nucleus is a highly crowded environment, filled with a multicomponent, polydisperse mixture of biopolymers and nuclear bodies dispersed in a viscous solvent. With volume fractions approaching 20%, excluded-volume interactions play a key role in determining the structure, dynamics, and function of macromolecules in vivo. Under such constraints, the ensembles of macromolecular conformations can differ substantially from those prevailing in dilute solutions. Crowding thus can affect protein and RNA folding, conformational stability, and reaction kinetics, as well as phase stability of macromolecular mixtures. From the perspective of soft matter physics, this chapter reviews recent studies on crowding in polymer-nanoparticle mixtures, seeking to demonstrate the utility of simple physical models for addressing challenging issues in cell biology. The focus is on applications of free-volume theory and Monte Carlo simulation, based on geometrical models of polymers as fluctuating spheres or ellipsoids. Ideal polymer coils respond to hard-sphere crowding agents by compactifying, reducing their radius of gyration, and becoming more spherical. At sufficiently high concentrations, polymers and crowders phase-separate. The goal of this review is to identify universal principles governing macromolecular crowding and to establish a general framework for future explorations of more realistic models that may include nonsteric (e.g., electrostatic) interactions.
authors.affiliation: Department of Physics, North Dakota State University, Fargo, North Dakota , USA. Electronic address: alan.denton@ndsu.edu.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Denton
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D053758:Nanoparticles / Q000737:chemistry / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D012313:RNA / Q000737:chemistry / Q000378:metabolism*
chemical_list: D012313:RNA
keywords: Cell nucleus; Free-volume theory; Macromolecular crowding; Monte Carlo simulation; Polymer–nanoparticle mixtures