Open AccessMultistate Multiconfiguration Quantum Chemical Computation of the Two-Photon Absorption Spectra of Bovine Rhodopsin
Author(s) -
Samira Gholami,
Laura Pedraza-González,
Xuchun Yang,
A. A. Granovsky,
Ilya N. Ioffe,
Massimo Olivucci
Publication year - 2019
Publication title -
the journal of physical chemistry letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.563
H-Index - 203
ISSN - 1948-7185
DOI - 10.1021/acs.jpclett.9b02291
Subject(s) - rhodopsin , degenerate energy levels , excited state , absorption spectroscopy , absorption (acoustics) , photon , population , physics , spectral line , atomic physics , chemistry , molecular physics , retinal , optics , quantum mechanics , biochemistry , demography , sociology
Recently, progress in IR sources has led to the discovery that humans can detect infrared (IR) light. This is hypothesized to be due to the two-photon absorption (TPA) events promoting the retina dim-light rod photoreceptor rhodopsin to the same excited state populated via one-photon absorption (OPA). Here, we combine quantum mechanics/molecular mechanics and extended multiconfiguration quasi-degenerate perturbation theory calculations to simulate the TPA spectrum of bovine rhodopsin (Rh) as a model for the human photoreceptor. The results show that the TPA spectrum of Rh has an intense S 0 → S 1 band but shows also S 0 → S 2 and S 0 → S 3 transitions whose intensities, relative to the S 0 → S 1 band, are significantly increased when compared to the corresponding bands of the OPA spectrum. In conclusion, we show that IR light in the 950 nm region can be perceived by rod photoreceptors, thus supporting the two-photon origin of the IR perception. We also found that the same photoreceptor can perceive red (i.e., close to 680 nm) light provided that TPA induces population of S 2 .