Wavepacket splitting and two-pathway deactivation in the photoexcited visual pigment isorhodopsin.
Isorhodopsin is the visual pigment analogue of rhodopsin. It shares the same opsin environment but it embeds 9-cis retinal instead of 11-cis. Its photoisomerization is three times slower and less effective. The mechanistic rationale behind this observation is revealed by combining high-level quantum-mechanical/molecular-mechanical simulations with ultrafast optical spectroscopy with sub-20 fs time resolution and spectral coverage extended to the near-infrared. Whereas in rhodopsin the photoexcited wavepacket has ballistic motion through a single conical intersection seam region between the ground and excited states, in isorhodopsin it branches into two competitive deactivation pathways involving distinct conical intersection funnels. One is rapidly accessed but unreactive. The other is slower, as it features extended steric interactions with the environment, but it is productive as it follows forward bicycle pedal motion.
IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci, 32, 20133 Milano (Italy); Center for Nano Science and Technology @Polimi, Italian Institute of Technology, Via G. Pascoli 70/3, 20133 Milano (Italy).
Dario
D
Polli
Oliver
O
Weingart
Daniele
D
Brida
Emiliano
E
Poli
Margherita
M
Maiuri
Katelyn M
KM
Spillane
Andrea
A
Bottoni
Philipp
P
Kukura
Richard A
RA
Mathies
Giulio
G
Cerullo
Marco
M
Garavelli
D004224:Diterpenes; D007536:Isomerism; D008958:Models, Molecular; D055668:Photochemical Processes; D011789:Quantum Theory; D012172:Retinaldehyde / Q000737:chemistry; D012243:Rhodopsin / Q000737:chemistry*; D013057:Spectrum Analysis
D004224:Diterpenes; C042882:isorhodopsin; C031390:9-cis-retinal; D012243:Rhodopsin; D012172:Retinaldehyde
conical intersections; isomerization; isorhodopsin; photochemistry; time-resolved spectroscopy