TY - JOUR
T1 - About the intrinsic photochemical properties of the 11-cis retinal chromophore
T2 - Computational clues for a trap state and a lever effect in Rhodopsin catalysis
AU - Cembran, Alessandro
AU - González-Luque, Remedios
AU - Serrano-Andrés, Luis
AU - Merchán, Manuela
AU - Garavelli, Marco
PY - 2007/7/1
Y1 - 2007/7/1
N2 - CASPT2//CASSCF/6-31G*computations are used on the singlet S 1 and S 2 states to map the photoisomerization process of the 11-cis retinal protonated Schiff base in vacuo and to characterize its optical properties. It is shown that the spectroscopic observations recorded in Rhodopsin are reproduced quite well, calling for a substantially neutral effect of the protein. Furthermore, a rationale is proposed for the unreactive population recently observed in Rhodopsin, which is here addressed to the accessible S 2 state, behaving as a trap. The experimental transient absorption and (absorption-wavelength dependent) emission are discussed and interpreted under the light of this novel model. Finally, a planarization of the β-ionone ring is observed on S 1, which may cause a steric lever effect into the protein pocket, thus assisting photoisomerization catalysis. The reported results constitute a solid reference for further studies aimed to rationalize the effect of the environment on the photochemical reactivity of retinal chromophores.
AB - CASPT2//CASSCF/6-31G*computations are used on the singlet S 1 and S 2 states to map the photoisomerization process of the 11-cis retinal protonated Schiff base in vacuo and to characterize its optical properties. It is shown that the spectroscopic observations recorded in Rhodopsin are reproduced quite well, calling for a substantially neutral effect of the protein. Furthermore, a rationale is proposed for the unreactive population recently observed in Rhodopsin, which is here addressed to the accessible S 2 state, behaving as a trap. The experimental transient absorption and (absorption-wavelength dependent) emission are discussed and interpreted under the light of this novel model. Finally, a planarization of the β-ionone ring is observed on S 1, which may cause a steric lever effect into the protein pocket, thus assisting photoisomerization catalysis. The reported results constitute a solid reference for further studies aimed to rationalize the effect of the environment on the photochemical reactivity of retinal chromophores.
KW - Ab initio calculations
KW - Conical intersections
KW - Photoisomerization
KW - Reaction mechanisms
KW - Retinal
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U2 - 10.1007/s00214-007-0259-9
DO - 10.1007/s00214-007-0259-9
M3 - Article
AN - SCOPUS:34547405249
SN - 1432-881X
VL - 118
SP - 173
EP - 183
JO - Theoretical Chemistry Accounts
JF - Theoretical Chemistry Accounts
IS - 1
ER -