Protein self-diffusion in crowded solutions

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 108; no. 29; pp. 11815 - 11820
• Main Authors: Roosen-Runge, Felix, Hennig, Marcus, Zhang, Fajun, Jacobs, Robert M.J, Sztucki, Michael, Schober, Helmut, Seydel, Tilo, Schreiber, Frank
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 19.07.2011; National Acad Sciences
• Subjects: Aqueous solutions; bovine serum albumin; Colloids; Condensed Matter; Diffusion; Diffusion coefficient; diffusivity; Ellipsoids; Fluid mechanics; General Physics; Hydrodynamics; Life Sciences; Macromolecular Substances - chemistry; Material concentration; Models, Chemical; Molecules; Neutron Diffraction; Neutron scattering; Neutrons; Physical Sciences; Physics; Proteins; Quantitative Methods; Rotation; Self diffusion; Serum Albumin, Bovine - chemistry; Soft Condensed Matter; translation (genetics); Water - chemistry
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1107287108

Macromolecular crowding in biological media is an essential factor for cellular function. The interplay of intermolecular interactions at multiple time and length scales governs a fine-tuned system of reaction and transport processes, including particularly protein diffusion as a limiting or driving factor. Using quasielastic neutron backscattering, we probe the protein self-diffusion in crowded aqueous solutions of bovine serum albumin on nanosecond time and nanometer length scales employing the same protein as crowding agent. The measured diffusion coefficient D(φ) strongly decreases with increasing protein volume fraction φ explored within 7% [less-than or equal to] φ [less-than or equal to] 30%. With an ellipsoidal protein model and an analytical framework involving colloid diffusion theory, we separate the rotational Dr(φ) and translational Dt(φ) contributions to D(φ). The resulting Dt(φ) is described by short-time self-diffusion of effective spheres. Protein self-diffusion at biological volume fractions is found to be slowed down to 20% of the dilute limit solely due to hydrodynamic interactions.