Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany.
Proc Natl Acad Sci U S A. 2011 Jul 19;108(29):11815-20. doi: 10.1073/pnas.1107287108. Epub 2011 Jul 5.
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% ≤ ϕ ≤ 30%. With an ellipsoidal protein model and an analytical framework involving colloid diffusion theory, we separate the rotational D(r)(ϕ) and translational D(t)(ϕ) contributions to D(ϕ). The resulting D(t)(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.
生物介质中的大分子拥挤是细胞功能的一个重要因素。在多个时间和长度尺度上的分子间相互作用的相互作用控制着精细的反应和传输过程系统，包括特别作为限制或驱动因素的蛋白质扩散。我们使用准弹性中子背散射，在纳秒时间和纳米长度尺度上探测牛血清白蛋白在拥挤水溶液中的蛋白质自扩散，使用相同的蛋白质作为拥挤剂。在 7%≤ϕ≤30%范围内，所测量的扩散系数 D(ϕ)随着蛋白质体积分数ϕ的增加而强烈减小。通过使用椭球蛋白质模型和涉及胶体扩散理论的分析框架，我们将旋转的 D(r)(ϕ)和平移的 D(t)(ϕ)贡献分离到 D(ϕ)中。所得到的 D(t)(ϕ)由有效球体的短时间自扩散来描述。在生物体积分数下的蛋白质自扩散由于仅由于流体动力学相互作用而被减缓至稀溶液极限的 20%。
