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性质，包括活细胞表面的那些分子。评估两个完全相同类型的分子在行为上的差异可以增强对细胞功能的理解。然而，单个分子的一个重要性质，即它们的自转速度，到目前为止还没有得到描述，因为这种自转速度非常快，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可以贴在细胞表面分子上的标签，以提供来自单个生物分子的光学信号。这个项目将使用其中的两个，纳米尺寸的圆柱形金纳米棒和蛋形荧光结构，称为量子点，来确定它们所连接的单个分子随时间的取向变化，从而确定其旋转速度。这些单分子的结果将被应用于以前的大量分子的平均性质的测量没有解决的问题。例如，一个这样的问题涉及启动特定生物效应的大型细胞表面分子复合体的实际大小。更广泛的影响该项目将为少数民族、第一代和女大学生提供在实验室接受博士教育的机会，该实验室已经培养了一批不同的科学家。这一群体包括妇女、代表不足的少数群体以及第一代和非传统大学生，包括本科生、研究生和博士后。项目活动将扩大学生和受训人员接触当代重要主题的机会，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向来访的科学家和本科生研究人员提供，并将为生物学研究提供重要的基础设施资源，特别是测量生物分子运动的独特设施。与该实验室之前的调查一样，这些研究将导致在美国生物物理学会会议上举行专门会议，在国际地点举办短期课程，并为大学生提供光学生物物理方法实验室模块。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，因为需要解决的问题之一是这一领域的悬而未决的问题。

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.