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      Coupled Methyl Group Rotation in FMN Radicals Revealed by Selective Deuterium Labeling.

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          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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          Author and article information

          Journal
          J Phys Chem B
          The journal of physical chemistry. B
          American Chemical Society (ACS)
          1520-5207
          1520-5207
          March 05 2020
          : 124
          : 9
          Affiliations
          [1 ] Fachbereich Physik, Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
          [2 ] Institut für Lebensmittelchemie, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany.
          [3 ] Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104 Freiburg, Germany.
          [4 ] Fakultät für Chemie, Technische Universität München, Lichtenbergstr. 4, 80247 Garching, Germany.
          Article
          10.1021/acs.jpcb.9b11331
          32011886
          9bc911f1-c508-49e1-8be4-042ff95dac35
          History

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