title: Anomalous subdiffusion is a measure for cytoplasmic crowding in living cells.
abstract: Macromolecular crowding dramatically affects cellular processes such as protein folding and assembly, regulation of metabolic pathways, and condensation of DNA. Despite increased attention, we still lack a definition for how crowded a heterogeneous environment is at the molecular scale and how this manifests in basic physical phenomena like diffusion. Here, we show by means of fluorescence correlation spectroscopy and computer simulations that crowding manifests itself through the emergence of anomalous subdiffusion of cytoplasmic macromolecules. In other words, the mean square displacement of a protein will grow less than linear in time and the degree of this anomality depends on the size and conformation of the traced particle and on the total protein concentration of the solution. We therefore propose that the anomality of the diffusion can be used as a quantifiable measure for the crowdedness of the cytoplasm at the molecular scale.
authors.affiliation: MEMPHYS-Center for Biomembrane Physics, Physics Department, University of Southern Denmark, Campusvej 55, Odense M, Denmark.
authors.forename: Matthias
authors.initials: M
authors.lastname: Weiss
authors.forename: Markus
authors.initials: M
authors.lastname: Elsner
authors.forename: Fredrik
authors.initials: F
authors.lastname: Kartberg
authors.forename: Tommy
authors.initials: T
authors.lastname: Nilsson
mesh_terms: D003198:Computer Simulation; D003593:Cytoplasm / Q000737:chemistry* / Q000378:metabolism*; D003911:Dextrans / Q000737:chemistry* / Q000378:metabolism*; D004058:Diffusion; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances; D008954:Models, Biological; D008956:Models, Chemical; D010316:Particle Size
chemical_list: D003911:Dextrans; D046911:Macromolecular Substances