PHYS 363 |
| We have investigated geometries and excitation energies of bovine rhodopsin and some of its mutants in their protein environments by hybrid quantum mechanical/molecular mechanical ONIOM calculations. TD-B3LYP/AMBER calculations reproduce the experimental absorption maximum of rhodopsin (500 nm) and predict spectral shifts due to mutations within 10 nm. Glu113 electrostatics shifts the first excitation energy to blue by ca. 30 kcal/mol. The other amino acids have no net effect on the first excitation energy of the native rhodopsin. However, they individually polarize the charge distribution within the chromophore. This electronic polarization effect is necessary for reproducing experimental bond length alternation along the polyene chain in protonated Schiff-base retinal, which correlates with the computed first excitation energy, and for the calculation of accurate excitation energies and spectral shifts in mutants. The protonation state and conformation of mutated residues affect electronic spectrum significantly. |
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PHYS Poster Session - Multiscale Modeling in Biophysics
7:30 PM-10:00 PM, Wednesday, April 9, 2008 Morial Convention Center -- Hall A, Poster
Division of Physical Chemistry |