Spectroscopy and photophysics of flavin-related compounds: 5-deaza-riboflavin

Insińska-Rak, Małgorzata; Sikorska, Ewa; Bourdelande, J. L.; Khmelinskii, Igor; Prukała, Wiesław; Dobek, Krzysztof; Karolczak, Jerzy; Machado, I. Ferreira; Ferreira, L. F. Vieira; Komasa, Anna; Worrall, David R.; Sikorski, Marek

doi:10.1016/j.molstruc.2005.09.005

Cited by 25 publications

(19 citation statements)

References 31 publications

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“…The calculated order of excited states is thus analogous in the singlet and triplet manifolds. Overall, the present QM(DFT/MRCI)/MM results for the protein‐embedded 5DFMN chromophore are quite close to the TD‐DFT results for isolated 5DFMN13a and to the DFT/MRCI results for microsolvated 5DFMN in a COSMO continuum solvent 13b…”

Section: Resultssupporting

confidence: 77%

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Photophysics of Structurally Modified Flavin Derivatives in the Blue‐Light Photoreceptor YtvA: A Combined Experimental and Theoretical Study

Silva-Junior¹,

Мansurova²,

Gärtner³

et al. 2013

ChemBioChem

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The light-induced processes of two flavin mononucleotide derivatives (1- and 5-deaza flavin mononucleotide, 1DFMN and 5DFMN), incorporated into the LOV domain of YtvA protein from Bacillus subtilis, were studied by a combination of experimental and computational methods. Quantum mechanics/molecular mechanics (QM/MM) calculations were carried out in which the QM part was treated by density functional theory (DFT) using the B3LYP functional for geometry optimizations and the DFT/MRCI method for spectroscopic properties, whereas the MM part was described by the CHARMM force field. 1DFMN is incorporated into the protein binding site, yielding a red-shifted absorption band (λ(max) =530 nm compared to YtvA wild-type λ(max) =445 nm), but does not undergo any LOV-typical photoreactions such as triplet and photoadduct formation. QM/MM computations confirmed the absence of a channel for triplet formation and located a radiation-free channel (through an S₁/S₀ conical intersection) along a hydrogen transfer path that might allow for fast deactivation. By contrast, 5DFMN-YtvA-LOV shows a blue-shifted absorption (λ(max) =410 nm) and undergoes similar photochemical processes to FMN in the wild-type protein, both with regard to the photophysics and the formation of a photoadduct with a flavin-cysteinyl covalent bond. The QM/MM calculations predict a mechanism that involves hydrogen transfer in the T₁ state, followed by intersystem crossing and adduct formation in the S₀ state for the forward reaction. Experimentally, in contrast to wild-type YtvA, dark-state recovery in 5DFMN-YtvA-LOV is not thermally driven but can only be accomplished after absorption of a second photon by the photoadduct, again via the triplet state. The QM/MM calculations suggest a photochemical mechanism for dark-state recovery that is accessible only for the adduct with a C4a--S bond but not for alternative adducts with a C5--S bond.

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Section: Resultssupporting

confidence: 77%

“… [a] TD‐B3LYP/6‐31G(d) results in a vacuum, from ref. 13a. [b] DFT/MRCI results obtained for a microsolvated structure (four water molecules included) in a continuum solvent environment (COSMO).…”

Section: Resultsmentioning

confidence: 99%

Photophysics of Structurally Modified Flavin Derivatives in the Blue‐Light Photoreceptor YtvA: A Combined Experimental and Theoretical Study

Silva-Junior¹,

Мansurova²,

Gärtner³

et al. 2013

ChemBioChem

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“…The experimental studies have been assisted by various ab initio calculations. [34][35][36][37][38][39][40] In many cases, the first step of the photo-initiated dynamics consists of an ultrafast electron transfer from a donor to the excited flavin.…”

Section: Introductionmentioning

confidence: 99%

Unraveling the flavin-catalyzed photooxidation of benzylic alcohol with transient absorption spectroscopy from sub-pico- to microseconds

Megerle

Wenninger

Kutta

et al. 2011

Phys. Chem. Chem. Phys.

102

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Flavin-mediated photooxidations have been described for applications in synthetic organic chemistry for some time and are claimed to be a route to the use of solar energy. We present a detailed investigation of the involved photophysical and photochemical steps in methoxybenzyl alcohol oxidation on a timescale ranging from sub-picoseconds to tens of microseconds. The results establish the flavin triplet state as the key intermediate for the photooxidation. The initial step is an electron transfer from the alcohol to the triplet state of the flavin catalyst with, followed by a proton transfer in B6 ms. In contrast, the electron transfer involving the singlet state of flavin is a loss channel. It is followed by rapid charge recombination (t = 50 ps) without significant product formation as seen when flavin is dissolved in pure benzylic alcohol. In dilute acetonitrile/water solutions of flavin and alcohol the electron transfer is mostly controlled by diffusion, though at high substrate concentrations >100 mM we also find a considerable contribution from preassociated flavin-alcohol-aggregates. The model including a productive triplet channel and a competing singlet loss channel is confirmed by the course of the photooxidation quantum yield as a function of substrate concentration: We find a maximum quantum yield of 3% at 25 mM of benzylic alcohol and significantly smaller values for both higher and lower alcohol concentrations. The observations indicate the importance to perform flavin photooxidations at optimized substrate concentrations to achieve high quantum efficiencies and provide directions for the design of flavin photocatalysts with improved performance.

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“…Time-dependent density functional theory (TD-DFT) was found to be a robust and accurate method to investigate large organic molecules, for the calculation of excitation energies and oscillator strengths [5] and has recently met a certain success in the investigation of charged/radical dyes which take into account bulk solvation effects [6][7][8][9][10][11][12][13][14][15][16][17]. In this work 3,3,3 0 ,3 0 -tetramethyl-N,N 0 -diethylindocarbocyanine iodide (Dye I) was taken as a model to investigate the effect of the solvent upon absorption wavelengths (k max ) at the TD-DFT level, giving an excellent agreement between theory and experiment.…”

Section: Introductionmentioning

confidence: 99%