NANOSECOND TEMPERATURE-JUMP SAXS

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。列出的机构是 中心，不一定是研究者的机构。 当折叠的自由能障碍被消除，使得整个蛋白质系综可以沿着单个反应坐标进行时，发生下坡蛋白质折叠。 如果一种蛋白质只有少量 局部最小值具有其剩余的障碍被快速去除，中间结构可以在每个随后的时间点清楚地和直接地观察到，而不需要单分子研究。 有了足够的时间分辨率，一系列的这些观察可以收集到一个电影的蛋白质构象变化，使一步一步的比较对计算模型用于预测蛋白质折叠从序列。下坡折叠蛋白已被发现或工程化，从 已经开发了几种不同的折叠结构和高功率激光系统，以提供温度的突然升高（“T跃变”），其触发从冷变性状态的折叠。 光学 光谱学已经被用于观察蛋白质折叠中的局部结构变化，但是目前没有方法可用于以足够的时间分辨率记录全局蛋白质形状以捕捉蛋白质折叠中的局部结构变化。 中间构象在快速下坡折叠。 小角X射线散射（SAXS）可以提供关于溶液中蛋白质的低空间分辨率结构信息;然而， 现有方法的分辨率太慢而不能观察到快速折叠动力学。 我们正在先进光子源Bio-CAT SAXS光束线上开发激光温度跳跃装置，以直接测量快速折叠过程中的瞬时蛋白质结构。

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. Downhill protein folding occurs when free energy barriers to folding are eliminated so that an entire ensemble of proteins can proceed along a single reaction co-ordinate. If a protein with only small local minima has its remaining barriers are quickly removed, intermediate structures can be distinctly and directly observed at each following timepoint without the need for single-molecule study. With sufficient time resolution, a series of these observations can be collected into a movie of protein conformational change that enables step-by-step comparisons against computational models used to predict protein folds from sequence. Downhill folding proteins have been discovered or engineered from several different folded structures, and high-power laser systems have been developed to provide sudden increases in temperature ("T-jumps") which trigger folding from a cold-denatured state. Optical spectroscopy has been used to observe local structural changes in protein folding, but no methods are currently available for recording global protein shape with sufficient time resolution to catch the intermediate conformations during rapid downhill folding. Small Angle X-ray Scattering (SAXS) can provide low-spatial resolution structural information about proteins in solution; however the temporal resolution of existing approaches is far too slow to observe fast folding kinetics. We are developing a laser temperature-jump apparatus at the Advanced Photon Source Bio-CAT SAXS beamline to directly measure transient protein structures during fast folding processes.