CHEMICAL EXCHANGE BETWEEN CONFORMERS

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。子项目及 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。 动态交换正在被纳入缓慢松弛局部结构（SRLS）模型的软件中。这种新的动态过程允许氮氧自由基自旋标记物在两个或更多个自旋标记物经历不同旋转速率和排序的位点之间交换位置。这个项目的动机是我们最近的T4溶菌酶动力学的多频研究，我们已经清楚地区分了两个不同的构象的氮氧系链。然而，我们以前仅限于考虑在ESR时间尺度上的交换是静态的。在此假设下，发现必须采用不同的群体以在不同频率下实现可接受的谱拟合。我们认为这是由于ESR在不同频率下的有效时间尺度不同。 我们的新软件将使我们能够澄清这些问题，并获得构象交换率。

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. Dynamic exchange is being incorporated into the software for the Slowly Relaxing Local Structure (SRLS) model. This new dynamic process allows the nitroxide spin label to exchange positions between two or more sites where the spin label experiences different rotational rates and orderings. This project is motivated by our recent multifrequency study of T4 lysozyme dynamics where we have clearly differentiated two distinct conformers of the nitroxide tether. However, we previously were limited to considering the exchange to be static on the ESR time scale. Under this assumption it was found that different populations have to be employed to achieve acceptable spectral fits at different frequencies. We believe that this is a result of the different effective timescales of ESR at the different frequencies. Our new software will enable us to clarify these matters, and to obtain rates of conformational exchange.