Massimo Olivucci

Bowling Green University

Hosted by: Vincenzo Venditti

Organic Seminar

Abstract:

From photon to neuron: the molecular mechanism of the primary event in vision

Massimo Olivucci^1,2

¹Department of Biotechnology, Chemistry and Pharmacy, University of Siena, via A. Moro 2, I-53100 Siena, Italy. ²Department of Chemistry, Bowling Green State University, Overman Hall, Bowling Green, 43403 OH, USA.

The activation of rhodopsin, the light-sensitive G-protein coupled receptor responsible for dim-light vision in vertebrates, is driven by an ultrafast excited state double-bond isomerization with a quantum efficiency (Φ_cis-trans) of almost 70%. The origin of such a high light sensitivity, ultimately allowing the human eye to detect even single photons, is not understood. A key unanswered question is whether and how the level of synchronization between different receptor vibrational modes controls the Φ_cis-trans value. Here, we employ hundreds of quantum-classical trajectories to show that, 15 femtoseconds after photon absorption the excited state population of rhodopsin splits into subpopulations reacting with different velocities and leading to distinct contributions to Φ_cis-trans. We find that each subpopulation and Φ_cis-trans contribution, is associated with a different phase relationship between specific critical vibrational modes. We also show that the population splitting is modulated by the protein electrostatics, thus linking amino acid sequence variations to Φ_cis-trans modulation.

1. Schnedermann, C.; Yang, X.; Liebel, M.; Spillane, K. M.; Lungtenburg, J.; Fernandez, I.; Valentini, A.; Schapiro, I.; Olivucci, M.; Kukura, P.; Mathies, R. A. Nat. Chem. 2018, 10, 449-455.

2. Yang, X.; Manathunga, M.; Gozem, S.; Léonard, J.; Andruniów, T.; Olivucci, M. Nat. Chem. 2022, 14, 441-449.

3. Barneschi, L.; Marsili, E.; Pedraza-González, L.; Padula, D.; De Vico, L.; Kaliakin, D.; Blanco-González, A.; Ferré, N.; Huix-Rotllant, M.; Filatov, M.; Olivucci, M. Nat. Commun. 2022, 13, 6432.