Structure of the intersection space associated with ZIE photoisomerization of retinal in rhodopsin proteins.
In this paper we employ a CASSCF/AMBER quantum-mechanics/molecular-mechanics tool to map the intersection space (IS) of a protein. In particular, we provide evidence that the S1 excited-state potential-energy surface of the visual photoreceptor rhodopsin is spanned by an IS segment located right at the bottom of the surface. Analysis of the molecular structures of the protein chromophore (a protonated Schiff base of retinal) along IS reveals a type of geometrical deformation not observed in vacuo. Such a structure suggests that conical intersections mediating different photochemical reactions reside along the same intersection space. This conjecture is investigated by mapping the intersection space of the rhodopsin chromophore model 2-Z-hepta-2,4,6-trieniminium cation and of the conjugated hydrocarbon 3-Z-deca-1,3,5,6,7-pentaene.
Dipartimento di Chimica, Università di Siena, Via Aldo Moro, I-53100 Siena, Italy.
Annapaola
A
Migani
Adalgisa
A
Sinicropi
Nicolas
N
Ferré
Alessandro
A
Cembran
Marco
M
Garavelli
Massimo
M
Olivucci
D007536:Isomerism; D008958:Models, Molecular; D011487:Protein Conformation; D011789:Quantum Theory; D012160:Retina / Q000737:chemistry*; D012243:Rhodopsin / Q000737:chemistry*
D012243:Rhodopsin