title: Coupling and Decoupling of Rotational and Translational Diffusion of Proteins under Crowding Conditions.
abstract: Molecular motion of biopolymers in vivo is known to be strongly influenced by the high concentration of organic matter inside cells, usually referred to as crowding conditions. To elucidate the effect of intermolecular interactions on Brownian motion of proteins, we performed (1)H pulsed-field gradient NMR and fluorescence correlation spectroscopy (FCS) experiments combined with small-angle X-ray scattering (SAXS) and viscosity measurements for three proteins, αB-crystalline (αBc), bovine serum albumin, and hen egg-white lysozyme (HEWL) in aqueous solution. Our results demonstrate that long-time translational diffusion quantitatively follows the expected increase of macro-viscosity upon increasing the protein concentration in all cases, while rotational diffusion as assessed by polarized FCS and previous multi-frequency (1)H NMR relaxometry experiments reveals protein-specific behavior spanning the full range between the limiting cases of full decoupling from (αBc) and full coupling to (HEWL) the macro-viscosity. SAXS was used to study the interactions between the proteins in solution, whereby it is shown that the three cases cover the range between a weakly interacting hard-sphere system (αBc) and screened Coulomb repulsion combined with short-range attraction (HEWL). Our results, as well as insights from the recent literature, suggest that the unusual rotational-translational coupling may be due to anisotropic interactions originating from hydrodynamic shape effects combined with high charge and possibly a patchy charge distribution.
authors.affiliation: Institut für Physik, Martin-Luther-Universität Halle-Wittenberg , 06099 Halle (Saale), Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Roos
authors.affiliation: Institut für Physik, Martin-Luther-Universität Halle-Wittenberg , 06099 Halle (Saale), Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Ott
authors.affiliation: Experimentalphysik II, Universität Bayreuth , 95440 Bayreuth, Germany.
authors.forename: Marius
authors.initials: M
authors.lastname: Hofmann
authors.affiliation: Institut für Physik, Martin-Luther-Universität Halle-Wittenberg , 06099 Halle (Saale), Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Link
authors.affiliation: Experimentalphysik II, Universität Bayreuth , 95440 Bayreuth, Germany.
authors.forename: Ernst
authors.initials: E
authors.lastname: Rössler
authors.affiliation: Institut für Physik, Martin-Luther-Universität Halle-Wittenberg , 06099 Halle (Saale), Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Balbach
authors.affiliation: Institut für Physik, Martin-Luther-Universität Halle-Wittenberg , 06099 Halle (Saale), Germany.
authors.forename: Alexey
authors.initials: A
authors.lastname: Krushelnitsky
authors.affiliation: Institut für Physik, Martin-Luther-Universität Halle-Wittenberg , 06099 Halle (Saale), Germany.
authors.forename: Kay
authors.initials: K
authors.lastname: Saalwächter
mesh_terms: D000818:Animals; D002417:Cattle; D002645:Chickens; D004058:Diffusion; D004529:Egg White / Q000737:chemistry; D057446:Hydrodynamics; D009682:Magnetic Resonance Spectroscopy; D009113:Muramidase / Q000737:chemistry; D021381:Protein Transport; D011506:Proteins / Q000737:chemistry*; D012399:Rotation; D012542:Scattering, Radiation; D053838:Scattering, Small Angle; D012709:Serum Albumin / Q000737:chemistry; D012710:Serum Albumin, Bovine / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D014783:Viscosity; D014961:X-Ray Diffraction; D038203:alpha-Crystallin B Chain / Q000737:chemistry; D038201:alpha-Crystallins / Q000737:chemistry
chemical_list: D011506:Proteins; D012709:Serum Albumin; D038203:alpha-Crystallin B Chain; D038201:alpha-Crystallins; D012710:Serum Albumin, Bovine; D009113:Muramidase