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Modeling reaction routes from rhodopsin to bathorhodopsin
M G Khrenova1, A V Bochenkova, A V Nemukhin
1Department of Chemistry, MV Lomonosov Moscow State University, Moscow 119991, Russian Federation.
Proteins
|September 30, 2009
Summary
Quantum mechanical-molecular mechanical theory accurately models bathorhodopsin (BATHO) and rhodopsin (RHO) structures and spectra. This study reveals reaction pathways and a transition state for RHO to BATHO conversion, crucial for visual pigment function.
Area of Science:
- Biophysics
- Computational Chemistry
- Spectroscopy
Background:
- Rhodopsin (RHO) is a key visual pigment involved in light detection.
- Bathorhodopsin (BATHO) is a primary photoproduct in the rhodopsin functional cycle.
- Understanding the RHO to BATHO transition is vital for visual photochemistry.
Purpose of the Study:
- To calculate accurate structural and spectral properties of BATHO and RHO.
- To characterize the reaction pathway from RHO to BATHO.
- To investigate the thermal protein activation mechanism.
Main Methods:
- Quantum mechanical-molecular mechanical (QM/MM) theory was employed.
- Density Functional Theory (DFT) with PBE0/cc-pVDZ for QM and AMBER force field for MM.
- Advanced quantum chemistry methods for electronic excitation energies.
Main Results:
- Computed structural parameters and vibrational spectra (HOOP, C==C, C--C stretches) match experimental data for BATHO and RHO.
- Electronic excitation energies (S(0)-S(1)) were estimated for the chromophore within the protein matrix.
- A transition state structure for the RHO to BATHO rearrangement was identified.
Conclusions:
- The QM/MM approach provides accurate modeling of visual pigment photochemistry.
- The identified transition state supports a thermal activation route for RHO to BATHO conversion.
- This research enhances understanding of the initial steps in vision.
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