Retinal chromophore photoinduced molecular motion and reactivity: isolated conditions and counterion effects

Article type: Research Article

Authors: Garavelli, Marco^{a; 1; 2} | Bernardi, Fernando^a | Cembran, Alessandro^a | Olivucci, Massimo^b

Affiliations: [a] Dipartimento di Chimica “G. Ciamician”, Università di Bologna, Via Selmi 2, 40126 Bologna, Italy | [b] Istituto di Chimica Organica, Università di Siena, Via Aldo Moro, I-53100 Siena, Italy

Correspondence: [*] Corresponding author.

Note: [1] E-mail: [email protected].

Abstract: Recent, work in the field of biological photoreceptors has demonstrated that computational chemistry can be successfully applied to ultrafast photobiological problems. Here we revise the results of the photoisomerization path mapping of the protonated Schiff base of retinal: the chromophore of rhodopsin proteins. These studies have produced the two-state/two-mode model which provides a rationale for the photon-induced molecular motion in the isolated retinal chromophore. Such model represents a substantial revision of the previous models for the primary event in vision in animals and light driven proton-pumping in halobacteriae. New computational results will be presented, which model the effects of an external counterfoil on the photoisomerization paths. Energetic, electronic, stereoselectivity control and tuning-effects will be analyzed and discussed in terms of counterfoil positions. Both solution and protein experimental data are revised using the new reactivity model.

Keywords: Computational Photochemistry, Protonated Schiff Bases, Retinal, Photoisomerization, CASSCF, CASPT2, Ab-Initio

DOI: 10.3233/JCM-2002-23-419

Journal: Journal of Computational Methods in Sciences and Engineering, vol. 2, no. 3-4, pp. 431-439, 2002