Rotation of Single Cell Surface Protein Molecules Studied via Nanoparticle Probes

现代光学方法使研究人员能够确定单个生物分子的许多特性，包括活细胞表面的特性。评估两种完全相同类型的分子如何在行为上有所不同，增强了对细胞功能的理解。然而，单个分子的一个重要特性，即它们的旋转速率，迄今为止还没有被描述出来，因为这种旋转速度非常快，发生在千分之一秒或更短的时间内。尽管如此，细胞表面分子，特别是蛋白质的旋转是重要的，因为这些运动的变化反映了细胞如何从环境中获取信息。纳米技术最近提供了各种各样的标签，这些标签可以附着在细胞表面分子上，以提供来自单个生物分子的光信号。这个项目将使用其中的两种，纳米尺寸的圆柱形金纳米棒和称为量子点的蛋形荧光结构，来确定与时间相关的方向变化，从而确定它们所附着的单个分子的旋转速率。这些单分子的结果将被应用于以前对大量分子的性质进行平均测量而未解决的问题。例如，一个这样的问题涉及启动特定生物效应的大细胞表面分子复合物的实际大小。更广泛的影响该项目将为少数族裔、第一代和女大学生提供博士学位教育的机会，该实验室已经培养了一批不同的科学家。这个群体包括女性、未被充分代表的少数民族、第一代大学生和非传统大学生，包括本科生、研究生和博士后。项目活动将扩大学生和受训者对当代重要课题的接触，如纳米技术和单分子生物物理学。通过该项目开发的仪器资源将提供给访问科学家和本科生研究人员，并将为生物学研究提供重要的基础设施资源，特别是用于测量生物分子运动的独特设备。这些研究将与该实验室之前的调查一样，导致美国生物物理学会会议的专门会议，国际各地的短期课程，以及面向大学生的光学生物物理方法的实验室模块。该项目的一个社会效益将是增进对限制牲畜繁殖效率的机制的了解，因为要解决的主题之一来自这一领域尚未解决的问题。

Modern optical methods have allowed researchers to determine many properties of single biological molecules, including those on the surfaces of living cells. Evaluating how two molecules of the exact same type can differ in their behavior has enhanced understanding of cellular function. However, one important property of individual molecules, their rates of rotation, has so far escaped characterization since this rotation is extremely rapid, occurring in thousandths of a second or less. Nonetheless rotation of cell surface molecules, particularly proteins, is important since changes in these motions reflect how cells obtain information from their environment. Nanotechnology has recently provided a variety of tags that can be attached to cell surface molecules to provide optical signals from individual biomolecules. This project will employ two of these, nanometer sized cylindrical gold nanorods and eggshaped fluorescent structures called quantum dots, to determine time-dependent orientational changes, and hence rotation rates, of the individual molecules to which they are attached. These single-molecule results will be applied to questions that previous measurements averaging properties of large numbers of molecules together have left unresolved. An example, one such question concerns the actual sizes of large cell surface molecular complexes that initiate particular biological effects. Broader impactsThis project will provide Ph.D. educational opportunities to minority, first-generation and female college students in a laboratory that already trains a diverse group of scientists. This group has included women, under-represented minority individuals and first-generation and non-traditional college students at the undergraduate, graduate and postdoctoral levels. The project activities will broaden the exposure of students and trainees to important contemporary topics such as nanotechnology and singlemolecule biophysics. Instrumental resources developed through the project will be available to visiting scientists and to undergraduate researchers and will provide a significant infrastructural resource for biological research, in particular, unique facilities for measuring motions of biological molecules. Such studies will, as have previous investigations by this laboratory, lead to specialized sessions at the U.S. Biophysical Society meetings, short courses in international locations, and laboratory modules in optical biophysical methods for university students. One societal benefit of the project will be improved understanding of mechanisms limiting reproductive efficiency of livestock since one of the topics to be addressed arises from unresolved questions in this area.