学术报告：Protein self-diffusion in crowded solutions
题 目：Protein self-diffusion in crowded solutions报告人：Marcus Hennig (Ph.D, The Australian Nuclear Science and Technology Organisation)
时 间：3月16日上午10：00 （星期五）
地 点：嘉定园区学术活动中心302
报告简介：
Proteins are molecular machines crucial for the function of living cells. Some proteins occur in the cell membrane, whilst others, in particular globular proteins, occur freely in the extra- and intracellular environment. These globular proteins carry out their biological function in an environment filled with both other molecules of a multitude of shapes and sizes and ions. Such a highly concentrated suspension is termed crowded. Macromolecular crowding in biological media is a crucial 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. Employing quasielastic neutron backscattering, we measure the self-diffusion in crowded aqueous solutions of bovine serum albumin on nanosecond time and nanometer length scales using the same protein as crowding agent. Moreover, by means of small-angle x-ray scattering, we determine the shape of the protein in solution using an ellipsoid model. We observe that the diffusion coefficient D() strongly decreases with increasing protein volume fraction explored within 7% 30%. With an ellipsoid protein model and an analytical framework involving colloid diffusion theory, we separate the rotational Dr() and translational Dt() contributions to D(). The resulting Dt() is described by short-time self-diffusion of effective hard-spheres. We find that the protein self-diffusion at biological volume fractions is slowed down to 20% of the dilute limit solely due to hydrodynamic interactions. The applicability of a simple colloid diffusion model to the experimental data opens the field for future applications of neutron scattering, where inter alia internal protein dynamics can be reliably separated from global diffusive protein dynamics under crowding conditions.
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