Theoretical Investigation of the Optical Spectra of Organic Compounds in Natural Surrounding

Abstract

The hybrid multiscale approximation based on molecular dynamics, quantum mechanics, and statistical theory is used to generate profiles of electronic vibrational absorption and fluorescence bands of some organic compounds and biological objects whose photophysical properties specifically depend on external conditions. A temperature dependence of the spectrum width and intensity of transition to the long-wavelength band of benzene surrounded by cyclohexane molecules is demonstrated. Statistical broadband absorption spectra for estradiol in ethanol, hexane, and dimethyl sulfoxide have been obtained and analyzed at room temperature together with a wide spectrum of transitions to numerous excited states of Trp-cage miniprotein. The absorption and emission spectra of 9-cyan anthracene have been generated under various thermodynamic conditions. This allows changes in the spectral profile with increasing temperatures and pressure to be detected. A dependence of the tryptophan spectra on the protein microsurrounding is investigated. The possibility of charge transfer from tryptophan residue to the eupatorin molecule trapped by human serum albumin is analyzed. Spectral properties and charge transfer from the excited donor to acceptor states are calculated using the polarizable embedding approach for modeling of surrounding protein structure.