Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1/3, 119991 Moscow, Russian Federation.
J Chem Phys. 2021 Feb 14;154(6):065101. doi: 10.1063/5.0026475.
An enhanced interest in the phytochrome-based fluorescent proteins is explained by their ability to absorb and emit light in the far-red and infra-red regions particularly suitable for bioimaging. The fluorescent protein IFP1.4 was engineered from the chromophore-binding domain of a bacteriophytochrome in attempts to increase the fluorescence quantum yield. We report the results of simulations of structures in the ground S and excited S electronic states of IFP1.4 using the methods of quantum chemistry and quantum mechanics/molecular mechanics. We construct different protonation states of the biliverdin (BV) chromophore in the red-absorbing form of the protein by moving protons from the BV pyrrole rings to a suitable acceptor within the system and show that these structures are close in energy but differ by absorption bands. For the first time, we report structures of the minimum energy conical intersection points S/S on the energy surfaces of BV in the protein environment and describe their connection to the local minima in the excited S state. These simulations allow us to characterize the deactivation routes in IFP1.4.
对基于光敏色素的荧光蛋白的兴趣增强，是因为它们能够在远红和近红外区域吸收和发射光，特别适合生物成像。荧光蛋白 IFP1.4 是从细菌光色素的发色团结合域工程改造而来，旨在提高荧光量子产率。我们报告了使用量子化学和量子力学/分子力学方法对 IFP1.4 的基态 S 和激发态 S 电子态结构进行模拟的结果。我们通过将质子从 BV 吡咯环移动到系统内合适的受体中来构建蛋白质中红光吸收形式的 BV 发色团的不同质子化状态，并表明这些结构在能量上接近，但吸收带不同。我们首次报告了在蛋白质环境中 BV 的 S/S 能面上的最小能量交叉点 S/S 的结构，并描述了它们与激发态 S 局部最小值的连接。这些模拟使我们能够表征 IFP1.4 的失活途径。
