Quantum Mechanics/Molecular Mechanics Study on the Photoreactions of Dark‐ and Light‐Adapted States of a Blue‐Light YtvA LOV Photoreceptor

다국어 초록 (Multilingual Abstract)

The dark‐ and light‐adapted states of YtvA LOV domains exhibit distinct excited‐state behavior. We have employed high‐level QM(MS‐CASPT2)/MM calculations to study the photochemical reactions of the dark‐ and light‐adapted states. The photoreaction from the dark‐adapted state starts with an S1→T1 intersystem crossing followed by a triplet‐state hydrogen transfer from the thiol to the flavin moiety that produces a diradical intermediate, and a subsequent internal conversion that triggers a barrierless C−S bond formation in the S0 state. The energy profiles for these transformations are different for the four conformers of the dark‐adapted state considered. The photochemistry of the light‐adapted state does not involve the triplet state: photoexcitation to the S1 state triggers C−S bond cleavage followed by recombination in the S0 state; both these processes are essentially barrierless and thus ultrafast. The present work offers new mechanistic insights into the photoresponse of flavin‐containing blue‐light photoreceptors.
Elektronenstrukturrechnungen (QM(MS‐CASPT2)/MM) der YtvA‐LOV‐Domänen zeigen einen detaillierten Mechanismus für die Relaxationsprozesse des Dunkel‐ (über T1 Wasserstofftransfer und S0 C‐S‐Bindungsbildung) und des Licht‐adaptierten Zustands (S1 C‐S‐Bindungsspaltung und S0 Rekombination). Die Photochemie des Dunkel‐adaptierten Zustands ist abhängig vom Konformer. IC=Interne Konversion, ISC=Interkombination, FNM=Flavinmononukleotid.