Tailored vibrational structure theory for difference infrared spectra of photoactive flavoproteins

红外光谱具有提供生物分子系统的详细结构信息的潜力。然而，计算方法对于提取这些信息是必不可少的。例如，使用黄素（BLUF）蛋白的蓝光传感器的氢键网络在照射时的细微变化可以通过差分红外光谱来监测。然而，对于相关的结构变化还没有达成共识，并且当前的计算方法要么效率太低，要么太不准确，无法为像BLUF蛋白质这样大的系统提供差异红外光谱的可靠解释。计算方法可以预期为符合实验设置的计算方案提供最有益的精度-成本比：在差分光谱中，监测变化而不是全光谱。这意味着，为了解释这些光谱，只有有助于这种变化的振动才需要建模。对于BLUF蛋白质，这种变化仅为几厘米的倒数-对于氢键系统，这种精度需要非谐量子处理。为了达到这个精度，我们将建立多能级非谐振动结构方法。我们的方法将利用碎片和多尺度方法的势能面以及嵌入方案的振动波函数，包括振动耦合集群响应方法。

Infrared spectroscopy has the potential to provide detailed structural information on biomolecular systems. However, computational methods are indispensable for extracting this information. For example, the subtle changes in the hydrogen bonding network of the blue light sensor using flavin (BLUF) protein upon illumination can be monitored by difference infrared spectroscopy. Yet, there is no consensus on the associated structural changes and current computational methods are either too inefficient or too inaccurate to provide a reliable interpretation of the difference infrared spectra for a system as large as the BLUF protein. Computational methods can be expected to provide the most beneficial accuracy-to-cost-ratio for a computational scheme that complies with the experimental setup: In difference spectroscopies, change is monitored rather than full spectra. That means, for the interpretation of these spectra only vibrations that contribute to this change have to be modelled. For the BLUF protein, this change amounts to only a few reciprocal centimetres - an accuracy that for hydrogen-bonded systems requires anharmonic quantum treatments. To achieve this accuracy, we will establish multi-level anharmonic vibrational structure methodologies. Our methods will exploit fragmentation and multi-scale approaches in the potential energy surface as well as embedding schemes for the vibrational wave function including vibrational coupled cluster response methodologies.