TIME RESOLVED STUDIES OF HELIX COIL TRANSITION IN SMALL PEPTIDES

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 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了解大蛋白如何折叠非常重要。螺旋-线圈的转变在过去已经得到了广泛的研究，包括最近的理论和实验工作，以及涉及激光诱导T跳跃的方法的研究。虽然螺旋-线圈转变的详细机制已经开始浮出水面，但仍存在争议。在这项工作中，我们将使用激光诱导T-JUMP快速折叠/去折叠起始和时间分辨红外光谱来研究合成的19个残基丙氨酸螺旋多肽的螺旋-螺旋转变。实验结果将与理论模型预测进行比较。 众所周知，末端封端和多肽长度会极大地影响螺旋-线圈转变的热力学。然而，它们在确定螺旋-线圈转变动力学中的作用还没有得到广泛的研究，也不太清楚。动力学伊辛模型和考虑通过扩散跨越势垒的顺序动力学模型都预测螺旋形成时间单调地依赖于多肽的长度，随着松弛时间的增加而增加 链条长度。在这里，我们用时间分辨红外光谱结合激光诱导温度跳跃(T-JUMP)的方法研究了一系列不同长度(19-39个残基)的丙氨酸-α-螺旋肽的螺旋-螺旋转变动力学。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. 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.