SAXS-DETECTED DYNAMICS OF FAST-FOLDING PROTEINS

这个子项目是许多利用 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。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 这个正在进行的项目是先前的BioCAT项目的后续，该项目通过小角X射线散射和圆二色光谱的组合来研究λ阻遏物的快速折叠动力学（Dumont等人，Protein Science 15，2596-2604（2006））。 我们正在研究λ阻遏物和fyn SH 3的聚集，以获得分子之间的平均力的潜力，从而获得临界聚集核的大小。 临界核是衡量蛋白质聚集的一个重要指标，但很难确定。 我们还研究了折叠动力学的下坡折叠突变的λ阻遏物的停流小角X射线散射。 我们的目标是测试的假设，疏水相互作用的损失最终导致了“转身”的折叠速率。 我们最近为这个项目进行了第一次光束时间，下一次计划时间将在2007年2月。 我们已经完成了对蛋白质的辐射损伤测试，聚集研究所需的所有浓度研究（目前正处于数据建模阶段，以准备发表），以及一些下坡λ阻遏突变体的动力学测量。 接下来将对两种蛋白质进行更多的动力学研究，包括在不同最终变性剂浓度下的测量，以提供回转半径的温度依赖性和时间依赖性的完整图谱。

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. This ongoing project follows up on a previous BioCAT project to study fast folding dynamics of lambda repressor by a combination of small angle X-ray scattering and circular dichroism spectroscopy (Dumont et al., Protein Science 15, 2596-2604 (2006)). We are examining the aggregation of lambda repressor and of fyn SH3 to obtain the potential of mean force between molecules and hence the size of the critical aggregation nucleus. The critical nucleus is an important measure of protein aggregation, but difficult to determine. We are also studying the folding dynamics of a downhill-folding mutant of lambda repressor by stopped-flow small angle X-ray scattering. The goal is to test the hypothesis that loss of the hydrophobic interaction eventually leads to a "turn-around" in the folding rate. We recently had our first beam time for this project, with the next planned time coming up in February 2007. We have completed radiation damage test on the proteins, all the concentration studies needed for the aggregation study (which is now in a phase of modeling the data to prepare for publication), and some of the kinetics measurements for the downhill lambda repressor mutants. More kinetics, including measurements at different final denaturant concentrations will be taken for both proteins next, to provide a complete map of the temperature dependence and time dependence of the radius of gyration.