Red Shift in the Absorption Spectrum of Phototropin LOV1 upon the Formation of a Semiquinone Radical: Reconstructing the Orbital Architecture

• DOI: 10.1021/acs.jpcb.4c00397
• Publication Date: 2024-04-30T21:54:25Z
• Authors: Patrick Kurle-Tuc...; Christian Wiebeler; Lisa Köhler; Ruonan Qin; Ziyue Zhao; Mantas Šimėnas; Andreas Pöppl; Jörg Matysik
• Keywords: Bathochromic shift; Phototropin; Flavin mononucleotide

Flavin mononucleotide (FMN) is a ubiquitous blue-light pigment due to its ability drive one- and two-electron transfer reactions. In both light-oxygen-voltage (LOV) domains of phototropin from the green algae Chlamydomonas reinhardtii, FMN noncovalently bound. LOV1 cysteine-to-serine mutant (C57S), light-induced electron nearby tryptophan occurs, transient spin-correlated radical pair (SCRP) formed. Within this photocycle, nuclear hyperpolarization created by solid-state photochemically induced dynamic polarization (photo-CIDNP) effect. side reaction, stable protonated semiquinone (FMNH·) forms undergoing significant bathochromic shift first electronic transition 445 591 nm. The incorporation LOV1-C57S into an amorphous trehalose matrix, stabilizing radical, allows for application various magnetic resonance experiments at ambient temperatures, which are combined with quantum-chemical calculations. As result, absorption band explained lifting degeneracy molecular orbital energy levels electrons alpha beta spins in FMNH· additional electron.