TIME RESOLVED STUDIES OF HELIX COIL TRANSITION IN SMALL PEPTIDES

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 α-螺旋是蛋白质中常见的结构基序。因此，了解其折叠机制对于理解大蛋白质如何折叠非常重要。螺旋-线团转变在过去已经被广泛研究，包括最近的理论和实验努力以及涉及激光诱导T-跳跃方法的研究。虽然螺旋-卷曲转变的详细机制已经开始出现，但争议仍然存在。在这项工作中，我们将研究的螺旋-线圈的转变，在一个合成的19个残基的丙氨酸为基础的螺旋肽使用激光诱导的T-跳跃快速重折叠/展开启动和时间分辨红外光谱松弛测量。实验结果将与理论模型预测进行比较。 众所周知，末端帽和肽长度可以显著地影响螺旋-卷曲转变的热力学。然而，它们在确定螺旋-线团转变动力学中的作用尚未被广泛研究，也不太清楚。动力学伊辛模型和涉及通过扩散跨越屏障的序贯动力学模型都预测螺旋形成时间单调地依赖于肽长度，其中松弛时间相对于肽长度的增加而增加。 链长在这里，我们已经研究了一系列基于丙氨酸的α-螺旋肽的不同长度（19-39个残基），有和没有端帽，使用时间分辨红外光谱结合激光诱导温度跳跃（T-jump）引发方法的螺旋-卷曲转变动力学。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Alpha-helix is a common structural motif in proteins. Understanding its folding mechanism is therefore important for understanding how large proteins fold. The helix-coil transition has been studied extensively in the past, including recent theoretical and experimental efforts as well as studies involving laser-induced T-jump methods. Although a detailed mechanism of the helix-coil transition has begun to emerge, controversy still exists. In this work we are going to study the helix-coil transition in a synthetic 19 residue Ala-based helical peptide using laser-induced T-jump for rapid refolding/unfolding initiation and time-resolved infrared spectroscopy for relaxation measurements. Experimental results will be compared to theoretical model predictions. It is well-known that end caps and the peptide length can dramatically influence the thermodynamics of the helix-coil transition. However, their roles in determining the kinetics of the helix-coil transition have not been studied extensively and are less well understood. Kinetic Ising models and sequential kinetic models involving barrier crossing via diffusion all predict that the helix formation time depends monotonically on the peptide length with the relaxation time increasing with respect to increasing chain length. Here, we have studied the helix-coil transition kinetics of a series of Ala-based alpha-helical peptides of different length (19-39 residues), with and without end caps, using time-resolved infrared spectroscopy coupled with laser-induced temperature jump (T-jump) initiation method.