5-D CRYSTALLOGRAPHY, SPACE, TIME AND TEMPERATURE

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。 五维结晶学 时间分辨结晶学最适合于在原子长度尺度上实时跟踪反应。它结合了结晶学和化学动力学。已经做出了大量努力来收集在时间上连续的几个数量级的数据集。由此可以利用奇异值分解等先进的数学方法来推断中间体的结构和化学动力学机理。然而，事实证明，这些机制的几个候选者同样很好地解释了数据，因此它们是退化的。为了消除这种简并性，必须改变一个附加参数以确定描述唯一机制的唯一速率系数集。由于速率系数通常遵循阿累尼乌斯定律，因此需要改变温度。 因此，时间分辨结晶学，即4维--3个空间维度加上时间--将变成5维。 我们将首次使用以前用光谱和时间分辨结晶学手段很好地表征的光活性黄色蛋白的晶体来进行这类实验。利用奇异值分解，结构转变的驰豫时间将使用在每个温度下的结晶Laue数据的时间序列确定从-5℃到35℃的几个温度。最终，这将得到一组独特的、明显可区分的中间体，以及PYP光循环的相应机制。

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. 5-dimensional crystallography Time-resolved crystallography is most suited to follow reactions in real time and on the atomic length scale. It combines crystallography with chemical kinetics. Substantial effort has been made to collect data sets contiguous over several orders of magnitudes in time. From this the structures of the intermediates as well as the chemical kinetic mechanism may be deduced using advanced mathematical methods such as the singular value decomposition. However, it turns out, that several candidates of these mechanisms explain the data equally well, hence they are degenerate. To remove this degeneracy, an additional parameter has to be varied to determine a unique set of rate coefficients describing a unique mechanism. Since rate coefficients usually follow Arrhenius's law, the temperature needs to be varied. Hence time-resolved crystallography, which is 4-dimensional - 3 space dimensions plus the time- would become 5-dimensional. We will perform these kind of experiments for the first time using crystals of photo-active yellow protein, which was previously well characterized by means of spectroscopy and time-resolved crystallography. Using singular value decomposition, relaxation times for the structural transitions will be determined at several temperatures starting at -5 deg C up to 35 deg C using the time-series of crystallographic Laue data at each temperature. Ultimately, this will give a unique set of clearly distinguishable intermediates plus the corresponding mechanism of the PYP photocycle.