Polypeptides chain dynamics probed by fluorescence

蛋白质是由称为氨基酸的单位组成的链。科学家们对蛋白质很感兴趣，因为它们进行了许多使身体正常运作的关键过程。它们能够完成这些任务，要归功于它们折叠成的紧密而紧凑的结构。人们进行了大量的研究，试图描述蛋白质的结构，现在已经知道了许多蛋白质的结构。此外，由于人类基因组已经被破译，所有人类蛋白质的组成都是已知的。换句话说，起点（蛋白质组成）和终点（蛋白质结构）是已知的，但实际上对蛋白质链如何从开始到结束知之甚少。本提案旨在通过荧光标记多肽来绘制蛋白质的折叠过程。多肽是由氨基酸组成的长链，用作蛋白质模拟物。在溶液中，多肽经历可以用荧光探测的内部运动。特别是，荧光实验可以提供用荧光团标记的单个氨基酸在溶液中由链定义的体积内移动多远的信息。荧光标记多肽利用内部手表固有的任何荧光团构建。事实上，荧光团在一段明确的时间内被激发，这是由它的寿命决定的。任何荧光团的寿命都可以通过添加外部猝灭剂来调节。由于荧光实验只报告那些被激发的荧光团，并且由于实验手段可用于控制荧光团保持兴奋的时间，因此标记氨基酸探测的体积将作为时间的函数进行监测。这项研究将探索氨基酸在溶液中的迁移率，并提供氨基酸在多肽线圈的体积内作为时间函数可以移动多远的信息。这些实验有望提供有用的实验数据，可用于模拟蛋白质链如何在溶液中折叠。

Proteins are chains made of units called amino acids. Proteins are of interest to scientists because they conduct a number of key processes that enable the body to function. They achieve these tasks thanks to the tight and compact structure they fold into. A lot of research is done trying to characterize the structure of proteins and many protein structures are now known. Furthermore, since the human genome has been deciphered, the composition of all human proteins is known. In other words, the starting point (protein composition) and the end-point (protein structure) are known, but very little is actually known on how a protein chain goes from start to finish. This proposal aims at mapping out the folding process of proteins by using fluorescently labeled polypeptides. Polypeptides are long chains made of amino acids which are used as protein mimics. In solution, polypeptides undergo internal motions which can be probed by fluorescence. In particular, fluorescence experiments can provide information on how far a single amino acid labeled with a fluorophore moves within the volume defined by the chain in solution. The fluorescently labeled polypeptides take advantage of the internal watch inherently built with any fluorophore. As a matter of fact, a fluorophore is excited for a well-defined period of time which is determined by its lifetime. The lifetime of any fluorophore can be adjusted by addition of an external quencher. Since a fluorescence experiment reports solely on those fluorophores that are excited, and since experimental means are available to control the time fluorophores remain excited for, the volume probed by a labeled amino acid will be monitored as a function of time. This study will probe the mobility of amino acids in solution and provide information on how far an amino acid can move within the volume of the polypeptide coil as a function of time. These experiments are expected to provide useful experimental data that can be used to model how a protein chain folds in solution.