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Updated: Dec 29, 2025

Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry
Published on: October 18, 2019
Coupled Methyl Group Rotation in FMN Radicals Revealed by Selective Deuterium Labeling
Richard Brosi1, Boris Illarionov2, Lorenz Heidinger3
1Fachbereich Physik, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
Abstract:
Flavin semiquinones are common intermediate redox states in flavoproteins, and thus, knowledge of their electronic structure is essential for fully understanding their chemistry and chemical versatility. In this contribution, we use a combination of high-field electron nuclear double resonance spectroscopy and selective deuterium labeling of flavin mononucleotide (FMN) with subsequent incorporation as cofactor into a variant Avena sativa LOV domain to extract missing traits of the electronic structure of a protein-bound FMN radical. From these experiments, precise values of small proton hyperfine and deuterium nuclear quadrupole couplings could be extracted. Specifically, isotropic hyperfine couplings of -3.34, -0.11, and +0.91 MHz were obtained for the protons H(6), H(9), and H(7α), respectively. These values are discussed in the light of specific protein-cofactor interactions. Furthermore, the temperature behavior of the H(7α) methyl-group rotation elicited by its energy landscape was analyzed in greater detail. Pronounced interplay between the two methyl groups at C(7) and C(8) of FMN could be revealed. Most strikingly, this rotational behavior could be modulated by selective deuterium editing.
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