J 2016

Energetics of Photoinduced Charge Migration within the Tryptophan Tetrad of an Animal (6-4) Photolyase

CAILLIEZ, Fabien, Pavel MÜLLER, Thiago FIRMINO, Pascal PERNOT, Aurélien de la LANDE et. al.

Základní údaje

Originální název

Energetics of Photoinduced Charge Migration within the Tryptophan Tetrad of an Animal (6-4) Photolyase

Autoři

CAILLIEZ, Fabien, Pavel MÜLLER, Thiago FIRMINO, Pascal PERNOT a Aurélien de la LANDE

Vydání

J. Am. Chem. Soc. Washington, American Chemical Society, 2016, 0002-7863

Další údaje

Typ výsledku

Článek v odborném periodiku

Utajení

není předmětem státního či obchodního tajemství

Odkazy

Impakt faktor

Impact factor: 13.858

DOI

UT WoS

000370582900034
Změněno: 17. 2. 2016 16:09, Mgr. Pavel Müller

Anotace

Anglicky

Cryptochromes and photolyases are flavoproteins that undergo cascades of electron/hole transfers after excitation of the flavin cofactor. It was recently discovered that animal (6-4) photolyases, as well as animal cryptochromes, feature a chain of four tryptophan residues while other members of the family contain merely a tryptophan triad. Transient absorption spectroscopy measurements on Xenopus laevis (6-4) photolyase have shown that the fourth residue is effectively involved in photoreduction, but, at the same time could not unequivocally ascertain the final redox state of this residue. In this article, polarizable molecular dynamics simulations and constrained Density Functional Theory calculations are carried out to reveal the energetics of charge migration along the tryptophan tetrad. Migration towards the fourth tryptophan is found to be thermodynamically favorable. Electron transfer mechanisms are sought either through an incoherent hopping mechanism or through a multiple sites tunneling process. The Jortner-Bixon formulation of electron transfer theory is employed to characterize the hopping mechanism. The interplay between electron transfer and relaxation of protein and solvent is analyzed in detail. Our simulations confirm that ET in (6-4) photolyase proceed out-of-equilibrium. Multiple site tunneling is modelled with the recently proposed flickering resonance mechanism. Given the position of energy levels and the distribution of electronic coupling values, tunneling over three tryptophan residues may become competitive in some cases, although a hopping mechanism is likely to be the dominant channel. For both reactive channels, computed rates are very sensitive to starting protein configuration, suggesting that both can take place and eventually be mixed, depending on the state of the system when photoexcitation takes place.