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Interplay Between Locally Excited and Charge Transfer States Governs the Photoswitching Mechanism in Fluorescent Protein Dreiklang

submitted on 10.10.2020, 18:49 and posted on 12.10.2020, 10:48 by TIRTHENDU SEN, Yingying Ma, Igor Polyakov, Bella Grigorenko, Alexander Nemukhin, Anna I. Krylov
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.


NSF No. CHE-1856342,

RSF No. 17-13-01051


Email Address of Submitting Author


University of Southern California


United States

ORCID For Submitting Author


Declaration of Conflict of Interest

A.I.K. is the president and a part-owner of Q-Chem, Inc.