NANOSECOND TEMPERATURE-JUMP SAXS

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。 当折叠的自由能障碍被消除时，蛋白质发生下坡折叠，这样整个蛋白质集合就可以沿着单一的反应坐标进行。如果一种蛋白质只含有少量 局部极小值的剩余障碍被迅速消除，中间结构可以在随后的每个时间点清楚而直接地观察到，而不需要单分子研究。 有了足够的时间分辨率，一系列这样的观察可以被收集到蛋白质构象变化的电影中，从而能够逐步与用于根据序列预测蛋白质折叠的计算模型进行比较。下坡折叠蛋白已被发现或从 已经开发了几种不同的折叠结构和高功率激光系统，以提供温度的突然上升(T形跳跃)，从而触发从冷变性状态的折叠。光学 光谱学已被用来观察蛋白质折叠的局部结构变化，但目前还没有足够的时间分辨率来记录全球蛋白质形状的方法来捕捉 快速下坡褶皱过程中的中间构象。小角X射线散射(SAXS)可以提供蛋白质在溶液中的低空间分辨率结构信息，但时间分辨率不高 现有方法的分辨率太慢，无法观察快速折叠动力学。我们正在高级光子源Bio-CAT SAXS光束线上开发一种激光温度跳跃设备，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.