Symmetrical and nonsymmetrical chromophores with Tröger's base skeleton: chiroptical, linear, and quadratic nonlinear optical properties--a joint theoretical and experimental study.

We report on the novel chiral push-pull chromophores derived from 6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine (Tröger's base skeleton). The synthesis of symmetrical chromophores featuring two identical acceptors, as well as the synthesis of unsymmetrical chromophores featuring only one acceptor is given. Symmetrical chromophores were prepared in the enantiomerically pure form and their chiroptical properties were investigated. Second-order nonlinear optical (NLO) properties of new chromophores were investigated with the aid of hyper-Rayleigh scattering (HRS). The detailed theoretical analysis of the second-order NLO properties of the chromophores was also undertaken. The joint theoretical and experimental studies of chromophores derived from Tröger's base skeleton, in comparison with benchmark chromophores featuring a dimethylamino group as the donor, provided insight into the relationship between the structure of the new chromophores and their NLO properties.

A voltage-dependent fluorescent indicator for optogenetic applications, archaerhodopsin-3: Structure and optical properties from in silico modeling.

It was demonstrated in recent studies that some rhodopsins can be used in optogenetics as fluorescent indicators of membrane voltage. One of the promising candidates for these applications is archaerhodopsin-3. While it has already shown encouraging results, there is still a large room for improvement. One of possible directions is increasing the intensity of the protein's fluorescent signal. Rational design of mutants with an improved signal is an important task, which requires both experimental and theoretical studies. Herein, we used a homology-based computational approach to predict the three-dimensional structure of archaerhodopsin-3, and a Quantum Mechanics/Molecular Mechanics (QM/MM) hybrid approach with high-level multireference ab initio methodology (SORCI+Q/AMBER) to model optical properties of this protein. We demonstrated that this methodology allows for reliable prediction of structure and spectral properties of archaerhodopsin-3. The results of this study can be utilized for computational molecular design of efficient fluorescent indicators of membrane voltage for modern optogenetics on the basis of archaerhodopsin-3.