STRUCTURAL CHANGES AND MOTIONS OF SINGLE BIO-MOLECULES

该提案的广泛和长期目标是研究单个生物大分子（如蛋白质、DNA、RNA及其复合物）在平衡、折叠过程中、配体结合和催化过程中的结构变化和运动。单分子测量可以获得系综实验无法揭示的分子结构变化和运动的分布和时间轨迹信息，从而为我们对生物大分子的基本认识提供新的见解。这种分子理解是我们理解生物系统和各种疾病起源的关键，可以加快疾病治疗方法的开发和新生物材料的设计。具体而言，正在开发使用荧光显微镜研究单个生物大分子的新工具，并将其应用于包括蛋白质折叠，RNA折叠和核糖体翻译在内的问题。在折叠实验中，蛋白质或RNA将用两个相同的荧光分子或一对荧光供体和受体标记。蛋白质或RNA在折叠过程中的构象变化将导致荧光的变化。通过在各种条件下测量单个蛋白质或RNA分子的荧光时间轨迹，可以探索它们的结构和折叠动力学。在核糖体翻译实验中，核糖体复合物中的两种不同组分将被一对荧光供体和受体标记。在平移过程中两个组分之间的相对运动将导致供体和受体之间的荧光能量转移效率的变化。 通过改变标记方案和测量翻译过程中的荧光，可以获得核糖体翻译过程的分子细节。

DESCRIPTION The broad and long-term goal of the proposal is to study structural changes and motions of individual bio-macromolecules such as proteins, DNA, RNA and their complexes in equilibrium, during folding, upon ligand binding, and during catalysis. The single molecule measurements can yield information on the distributions and time trajectories of the structural changes and motion of molecules that can not be revealed by ensembles experiments, and thus provide new insights into our fundamental understanding of the bio-macromolecules. Such a molecular understanding is key to our understanding of the biological systems and the origin of various diseases and can speed up the development of cures to the diseases and the designing of new biological material. Specifically, new tools to study individual bio-macromolecules using fluorescence microscopy are being developed and being applied to problems including protein folding, RNA folding and ribosomal translation. In the folding experiments, the protein or RNA will be labeled with two identical fluorescence molecules or a pair of fluorescence donor and acceptor. The conformation changes of the protein or RNA during folding will lead to changes in the fluorescence. By measuring the fluorescence time-traces from the individual protein or RNA molecules under various conditions, their structures and folding kinetics can be explored. In the ribosomal translation experiment, two different components in the ribosome complex will be labeled with a pair of fluorescence donor and acceptor. The relative motion between the two components during the translation will lead to changes in the fluorescence energy transfer efficiency between the donor and the acceptor. By varying the labeling scheme and measuring the fluorescence during the translation, the molecular details of the ribosomal translation process can be obtained.