We present the results of high-level electronic structure and dynamics simulations
of the photoactive protein Dreiklang. With the goal to understand the details of
Dreiklang's photocycle, we carefully characterize the excited states of the ON- and
OFF-forms of Dreiklang. The key ?nding of our study is the existence of a lowlying
excited state of a charge-transfer (CT) character in the neutral ON form and
that population of this state, which is nearly isoenergetic with the locally excited
(LE) bright state, initiates series of steps ultimately leading to the formation of
the hydrated dark chromophore (OFF state). These results allow us to re?ne the
mechanistic picture of the Dreiklang's photocycle and photoactivation.
InstitutionUniversity of Southern California
ORCID For Submitting Author0000-0003-2913-5315
Declaration of Conflict of InterestA.I.K. is the president and a part-owner of Q-Chem, Inc.