Mesoscopic Aggregation of Folded Proteins

为了发挥它们的功能，蛋白质必须在活细胞的拥挤环境中运作，因此需要防止蛋白质聚集的机制。当这些机制失效时，就会发生镰状细胞性贫血或斑块形成等病理情况。另一方面，在某些情况下，特定类型的聚集实际上是可取的；例如，胰岛素存储在胰腺中，蛋白质存储在谷物中，以晶体的形式存在。制作蛋白质晶体仍然是确定蛋白质结构的唯一最重要的工具，这对于理解蛋白质的功能至关重要。令人惊讶的是，为了形成这些蛋白质聚集体，折叠的蛋白质分子必须首先组织成长寿命的富含蛋白质的液体簇，大小约为一微米：根据现有的相平衡范例，这样的介观簇不应该存在，也不应该在其他类似的系统中看到，比如胶体。该项目旨在阐明令人费解的介观团簇形成的分子机制和热力学基础。为了实现这一目标，该项目将结合卢布琴科和维基洛夫实验室的理论和实验努力，使用四种蛋白质作为模型系统：溶菌酶、血红蛋白、胰岛素和鲁马津合成酶。蛋白质-溶剂界面的水结构和瞬时蛋白质低聚物的形成在蛋白质相稳定中的作用将通过分子模拟来研究，并通过动态/静态光散射以及热力学和流变学的方法进行测试。蛋白质运输和低聚物形成之间的相互作用导致的团簇形成/衰变的丰富动力学将通过求解耦合扩散/平流的非线性动力学方案来计算，并与测量的团簇寿命和大小进行测试。解决浓缩蛋白质溶液中介观聚集体的重要问题在于生物、物理、化学和材料科学的交界处。此外，这项研究将是来自化学和化学工程系的理论和实验小组的密切合作。这些因素将结合在一起，为参与的学生和研究基础设施创造一个独特的多学科研究环境。考虑到休斯顿大学和大休斯顿地区的种族多样性，这项研究将增加几个代表性不足群体的教育机会，并促进他们参与高级研究。将利用现有的与当地作家和电台人士的合作来宣传这项研究的社会效益。除了这项研究的基础和临床意义外，它的好处还包括为制造新材料和提高作物的营养价值开辟了新的潜在途径。该项目由分子和细胞生物科学部的分子生物物理学和物理学部的生命系统物理学项目共同支持。

To perform their function, proteins must operate in the crowded environment of a living cell, thus requiring mechanisms that prevent protein aggregation. When these mechanisms fail, pathological conditions, such as sickle cell anemia or plaque formation, take place. In some cases, on the other hand, specific types of aggregation are actually desirable; examples including storage of insulin in the pancreas and protein in grains, in the form of crystals. Making protein crystals remains the single most important tool for protein structure determination, which is crucial for understanding protein function. It comes as a surprise that for those protein aggregates to form, folded protein molecules must first organize into long-lived clusters of a protein-rich liquid that are about a micron in size: According to the existing paradigms of phase equilibrium, such mesoscopic clusters should not exist, nor have they been seen in other similar systems such as colloids. The project aims to elucidate the molecular mechanism and the thermodynamic basis of how the puzzling mesoscopic clusters form. To accomplish this goal, the project will combine the theoretical and experimental efforts of the Lubchenko and Vekilov labs using four proteins as model systems: lysozyme, hemoglobin, insulin, and lumazine synthase. The roles of water structuring at the protein-solvent interface and the formation of transient protein oligomers in the stabilization of the protein-rich phase will be investigated by molecular modeling and tested by means of dynamic/static light scattering and thermodynamic and rheological characterizations. The rich kinetics of the formation/decay of clusters resulting from the interplay between protein transport and oligomer formation will be worked out by solving non-linear kinetic schemes coupled with diffusion/advection and tested against measured life-times and sizes of the clusters. The solution of the important problem of mesoscopic aggregates in concentrated protein solutions lies at the interface of biology, physics, chemistry, and materials science. In addition, this research will be a close collaboration between a theoretical and experimental group from departments of chemistry and chemical engineering. These factors will combine to create a unique multidisciplinary research environment for participating students and research infrastructure. Considering the ethnic diversity at the University of Houston and in the greater Houston area, the research will enhance the educational opportunities in several underrepresented groups and promote their participation in advanced research. Existing collaborations with local writers and radio personalities will be utilized to publicize the societal benefits of the research. In addition to the fundamental and clinical significance of the research, its benefits include new potential routs for manufacturing novel materials and improving the nutritional value of crops. This project is jointly supported by Molecular Biophysics in the Division of Molecular and Cellular Biosciences and by the Physics of Living Systems program in the Physics Division.