Molecular photophysics and laser control: Small molecules to fluorescent proteins

这项研究的重点是开发和利用理论和计算方法，以了解和预测作为生物成像和新材料基础的分子的结构和性质，以及控制分子量子动力学。实验测量需要补充的理论和计算研究来解释，更重要的是，将观察到的行为推广到其他系统。虽然重点是详细了解激发电子态，但相应的光谱性质(单光子吸收、双光子吸收、荧光、磷光、…)，和潜在的动力学，需要研究的问题是多样的：(1)荧光蛋白是分子和细胞生物学中有用的生物机制、功能和结构的探针。人们对设计具有良好双光子吸收的光子晶体产生了极大的兴趣。我们将基于非规范氨基酸(NCAA)对FP进行计算筛选，以确定其双光子吸收特性。由于将NCAA结合到蛋白质中在实验上是一项具有挑战性的任务，因此对有前途的系统的计算指导至关重要。(2)我们将探索最近合成的荧光碱基类似物(天然碱基是非荧光的)，以合理地解释结构和光物理性质之间的联系。为了评估它们在生物成像中的应用，我们将研究它们与天然碱基的结合以及随后对吸收/荧光性质的影响。(3)将开发计算工具来模拟共振拉曼光谱。(4)BODIPY分子家族由于具有吸收波长可调、消光系数大、量子产率高等优良的光物理性质而得到了广泛的应用。取代的BODIPY和BODIPY二聚体将被用于各种用途，如成像、分子光子学…(5)计算基于含铋化合物的新型磷光材料的光物理性质；合理设计光谱特性得到改善的新材料可以省去无数的实验。(6)利用定制的激光场控制量子动力学在理论上和实验上都是站得住脚的。形状激光光源从中红外到紫外光的不断发展导致了对各种光物理和光化学现象的控制，例如振转和/或电子态布居转移，光异构化。对这些实验的一个重要补充是对导致控制的机制(S)的详细了解。这项拟议的研究将进一步开发和应用检测多原子分子中激光控制的方法。应用将包括光异构化，特别是光可切换蛋白质。

The research is focused on the development and utilization of theoretical and computational methods for understanding and predicting the structure and properties of molecules underlying biological imaging and new materials as well as for controlling molecular quantum dynamics. Experimental measurements require complementary theoretical and computational study to interpret, and, more importantly, to generalize the observed behaviour to other systems. While the emphasis is on a detailed understanding of excited electronic states, corresponding spectroscopic properties (1-photon absorption, two-photon absorption, fluorescence, phosphorescence,…), and underlying dynamics, the problems to be studied are diverse: (1) Fluorescent proteins are useful probes of biological mechanisms, functions, and structures in molecular and cell biology. There has been great interest in designing FPs with excellent two-photon absorption. We will screen computationally FPs based on non-canonical amino acids (ncAAs) for their two-photon absorption properties. Since the incorporation of ncAAs into proteins is a challenging task experimentally, computational guidance on promising systems is critically important. (2) We will explore recently synthesized fluorescent nucleobase analogs (the natural nucleobases are non-fluorescent) to rationalize the connections between structure and photophysical properties. To assess their use in biological imaging, we will study their binding to natural nucleobases and subsequent effects on absorption/fluorescence properties. (3) Computational tools will be developed for simulating resonance Raman spectra. (4) The BODIPY family of molecules is used widely due to their excellent photophysical properties, i.e., tunable absorption wavelengths, large extinction coefficients, and high quantum yields. Substituted-BODIPY and BODIPY dimers will be examined for a variety of uses, e.g., imaging, molecular photonics… (5) We will compute the photophysical properties of new phosphorescent materials based on bismuth-containing compounds; the rational design of new materials with improved spectral characteristics can save countless experiments. (6) Using tailored laser fields to control quantum dynamics is well-established theoretically and experimentally. The on-going development of shaped laser sources from the mid-infrared to the ultraviolet has lead to the control of a diversity of photophysical and photochemical phenomena, e.g., rovibrational and/or electronic state population transfer, photoisomerization. An important complement to these many experiments is a detailed understanding of the mechanism(s) leading to control. The proposed research will further develop and apply methods for examining laser control in polyatomic molecules. Applications will include photoisomerization and, in particular, photoswitchable proteins.