Serial Femtosecond Crystallography of Optogenetic Function

设计可以遗传编码的合成光敏材料的能力为生物学家提供了感知和控制生物功能和环境的手段和机会。为了了解这些材料的功能，最近已经可以使用X射线晶体学对光诱导运动进行非常快速的“快照”，这甚至可以用于非常短的时间尺度，仍然涉及激发的电子（飞秒时间尺度）。新的第四代光源现在可以用来记录这样的“分子电影”，这是一项突破性的技术，我们只是最近才证明。在不久的将来，我们预计能够录制更高质量的电影，因为位于汉堡的欧洲XFEL将允许录制更多数据。以前我们只能使用激光光谱技术，现在我们可以直接“观察”蛋白质激活后的第一次运动。已知的是，涉及感测或激活（经由“致动”）的生物反应的“结果”在这些发生在通常小于皮秒的时间尺度上的最初运动中确定。例如，在双向光致变色荧光蛋白的情况下，在一个方向上的转换效率在30%是优异的，而在相反方向上的转换效率在小于0.05%是差的，潜在地限制了光遗传学应用。因此，我们能够提出这样一个问题，即是什么决定了反应结果的这种巨大差异，并提供结构和动力学信息，这些信息对于反馈合理的光遗传学设计非常有价值。

The ability to design synthetic light-sensitive materials that can be genetically encoded provides biologists the means and opportunity to sense and control biological function and environment. In order to learn how these materials function it has very recently become possible to make very fast 'snapshots' of the light-induced motions using X-ray crystallography, which is even possible for very short time scales that still involves the excited electrons (on femtosecond time scale). Novel 4th generation light sources can now be used to record such 'molecular movies' which is a breakthrough technology that we only very recently demonstrated. In the very near future we anticipate being able to record even better quality movies, as the European XFEL in Hamburg that allows much more data to be recorded will start user operation. Where previously we could only use laser spectroscopy techniques we can now actually 'watch' the very first motions of proteins directly after activation. It is known that the 'outcome' of biological reactions involving either sensing or activation (via 'actuation') is determined in these very first motions that occur on time scales typically less than picoseconds. For example, in the case of a bi-directional photochromic fluorescent protein the efficiency of switching in one direction is excellent at 30%, while the efficiency of switching in the reverse direction is poor at less than 0.05%, potentially limiting optogenetics applications. We are thus in a position to ask the question what determines this dramatic difference in the outcome of the reactions, and provide structural and dynamical information that will be highly valuable for feeding back for rational optogenetics design.