This work shows that very high-field EPR spectroscopy allows a rather accurate determination of the g-tensor of protein radicals, including C-centered ones, and thus may be used as a probe for distinguishing a tyrosyl-, a glycyl-, or a tryptophanyl-radical. In this paper, we report the first complete analysis of the g-tensor of glycyl radical enzymes (anaerobic ribonucleotide reductase, pyruvate formate lyase, and benzylsuccinate synthase), thus providing new information on their EPR properties. Because the g-anisotropy is small, the complete resolution of the g-tensor could be only obtained at very high field (18.8 T).
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