Quantum dynamics of the femtosecond photoisomerization of retinal in bacteriorhodopsin

M. Ben-Nun, Ferenc Molnar, Hui Lu, James C. Phillips, Todd J. Martínez, Klaus Schulten

Research output: Contribution to journalArticlepeer-review


The membrane protein bacteriorhodopsin contains all-trans-retinal in a binding site lined by amino acid side groups and water molecules that guide the photodynamics of retinal. Upon absorption of light, retinal undergoes a subpicosecond all-trans → 13-cis phototransformation involving torsion around a double bond. The main reaction product triggers later events in the protein that induce pumping of a proton through bacteriorhodopsin. Quantum-chemical calculations suggest that three coupled electronic states, the ground state and two closely lying excited states, are involved in the motion along the torsional reaction coordinate Φ. The evolution of the protein-retinal system on these three electronic surfaces has been modelled using the multiple spawning method for non-adiabatic dynamics. We find that, although most of the population transfer occurs on a timescale of 300 fs, some population transfer occurs on a longer timescale, occasionally extending well beyond 1 ps.

Original languageEnglish (US)
Pages (from-to)447-462
Number of pages16
JournalFaraday Discussions
StatePublished - 1998

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry


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