PICOSECOND TIME-RESOLVED LAUE CRYSTALLOGRAPHY

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 我们的目标是使用皮秒时间分辨劳厄结晶学技术来研究蛋白质中的生物物理过程。具体地说，我们将使用强的短持续时间激光脉冲来触发蛋白质晶体的结构变化，并将使用一系列X射线快门从同步加速器脉冲序列中分离出单个X射线脉冲来探索其结构演变。通过获取激光光解后特定时刻的衍射数据，我们可以构建时间分辨率仅受X射线脉冲持续时间限制的蛋白质结构的快照，时间分辨率约为100ps。我们的目标是解决大量的生物物理问题，包括高度保守的残基在蛋白质途径中的功能作用，配体从蛋白质活性部位迁移到蛋白质活性部位，以及调节或控制变构调节的相关结构变化。为了获得尽可能高质量的数据，我们首先将重点放在结构变化是可逆的蛋白质系统上。包括肌红蛋白和血红蛋白在内的配体结合的血红素蛋白是这些生物物理研究的理想模型体系。当CO被用作O2的替代物时，配体可以高量子效率地从血红素中光解离，从而触发一系列可以从结构上研究的事件。由于解离的配体在ms时间尺度上以双分子的方式重新结合到血红素上，结构返回到其初始状态，这个过程可以重复数千次。因此，这些模型系统是进行这些生物物理研究的理想选择。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. We aim to employ the technique of picosecond time-resolved Laue crystallography to study biophysical processes in proteins. Specifically we will use intense short-duration laser pulses to trigger a structural change in a protein crystal and will probe its structural evolution with single X-ray pulses isolated from the synchrotron pulse train using a sequence of X-ray shutters. By acquiring diffraction data at a well-defined instant in time after laser photolysis we can construct a snapshot of the proteins structure with time resolution limited only by the duration of the X-ray pulse which is of the order of 100 ps. We aim to address numerous biophysical questions including the functional role of highly conserved residues in proteins pathways for ligand migration to and from the proteins active site and the correlated structural changes that mediate or control allosteric regulation. To obtain the highest quality data possible we will focus initially on protein systems whose structural changes are reversible. Ligand-binding heme proteins including myoglobin and hemoglobin are ideal model systems for these biophysical investigations. When CO is used as a surrogate for O2 the ligand can be photodissociated from the heme with high quantum efficiency thereby triggering a sequence of events that can be studies structurally. Because the dissociated ligands rebind to the heme bimolecularly on the ms time scale the structure returns to its starting state and the process can be repeated thousands of times. Thus these model systems are ideal for pursuing these biophysical studies.