Calculation of the Geometries and Infrared Spectra of the Stacked Cofactor Flavin Adenine Dinucleotide (FAD) as the Prerequisite for Studies of Light-Triggered Proton and Electron Transfer.

Martina Kieninger,Tilman Kottke,Oscar N Ventura

doi:10.3390/biom10040573

Martina Kieninger, Tilman Kottke + Show 1 more

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https://doi.org/10.3390/biom10040573

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Journal: Biomolecules	Publication Date: Apr 9, 2020
Citations: 1	License type: CC BY 4.0

Affiliation: Bielefeld University

Abstract

Flavin cofactors, like flavin adenine dinucleotide (FAD), are important electron shuttles in living systems. They catalyze a wide range of one- or two-electron redox reactions. Experimental investigations include UV-vis as well as infrared spectroscopy. FAD in aqueous solution exhibits a significantly shorter excited state lifetime than its analog, the flavin mononucleotide. This finding is explained by the presence of a “stacked” FAD conformation, in which isoalloxazine and adenine moieties form a π-complex. Stacking of the isoalloxazine and adenine rings should have an influence on the frequency of the vibrational modes. Density functional theory (DFT) studies of the closed form of FAD in microsolvation (explicit water) were used to reproduce the experimental infrared spectra, substantiating the prevalence of the stacked geometry of FAD in aqueous surroundings. It could be shown that the existence of the closed structure in FAD can be narrowed down to the presence of only a single water molecule between the third hydroxyl group (of the ribityl chain) and the N7 in the adenine ring of FAD.

Highlights

Flavin cofactors, like flavin adenine dinucleotide (FAD), are important electron shuttles in living systems
This study provided evidence for an electron transfer from adenine to isoalloxazine by a bleach of the adenine stretch at 1623 cm−1, which rises with 1.1 ps and decays with 9 ps
In order to compare the structures of FAD in aqueous solution with structures which may be adopted by FAD in polar aprotic solvents, the Molecular dynamic (MD) calculations were repeated with dimethyl sulfoxide (DMSO)

Summary

Introduction

Like flavin adenine dinucleotide (FAD), are important electron shuttles in living systems. Flavin cofactors catalyze a wide range of one- or two-electron redox reactions. Photoreception involves mostly three families of flavoproteins: LOV (light, oxygen, voltage) proteins [1], cryptochromes [2] and BLUF (sensors of blue light using flavin) proteins [3]. These proteins act as blue-light-receptors in many organisms. Photoenzymes with flavin cofactor are DNA photolyases, which repair UV light-damages of DNA [6], and the fatty acid decarboxylase [7]. The cofactor is not covalently bound but in a dynamic equilibrium with the solution [8]

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