posted on 2020-03-04, 19:44authored bySatu Mustalahti, Dmitry Morozov, Hoi Ling Luk, Rajanish R. Pallerla, Pasi Myllyperkiö, Mika Pettersson, Petri M. Pihko, Gerrit Groenhof
Photoactivation in
the Photoactive Yellow Protein, a bacterial
blue-light photoreceptor, proceeds via photoisomerization of the double
CC bond in the covalently attached chromophore. Quantum chemistry
calculations, however, have suggested that in addition to double-bond
photoisomerization, the isolated chromophore and many of its analogues
can isomerize around a single C–C bond as well. Whereas double-bond
photoisomerization has been observed with X-ray crystallography, experimental
evidence of single-bond photoisomerization is currently lacking. Therefore,
we have synthesized a chromophore analogue, in which the formal double
bond is covalently locked in a cyclopentenone ring, and carried out
transient absorption spectroscopy experiments in combination with
nonadiabatic molecular dynamics simulations to reveal that the locked
chromophore isomerizes around the single bond upon photoactivation.
Our work thus provides experimental evidence of single-bond photoisomerization
in a photoactive yellow protein chromophore analogue and suggests
that photoisomerization is not restricted to the double bonds in conjugated
systems. This insight may be useful for designing light-driven molecular
switches or motors.