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Detection of Scalar Couplings Across NH···OP and OH···OP Hydrogen Bonds in a Flavoprotein

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journal contribution
posted on 2000-09-08, 00:00 authored by Frank Löhr, Stephen G. Mayhew, Heinz Rüterjans
Hydrogen bonding plays a major role in the tight binding of the FMN cofactor in flavodoxins. The present NMR investigation provides direct experimental evidence for hydrogen bonds involving the phosphate moiety of FMN in Desulfovibrio vulgaris flavodoxin. Several trans-hydrogen bond J couplings between the phosphorus nucleus and backbone amide as well as side chain hydroxyl protons of the apoprotein have been detected. It is shown that relaxation interference between 1H chemical shift anisotropy and 1H−31P dipolar interactions can also lead to correlations of these nuclei in HMBC spectra. The size of the 2hJPH coupling constants was determined using a simple 31P-detected quantitative J correlation experiment. For at least one amide group a scalar three-bond coupling between the phosphorus and nitrogen has been observed in a [15N,1H]-TROSY-type 15N−{31P} spin−echo difference experiment. With approximately 1.7 Hz its magnitude is larger than that of the 31P−1H couplings, which ranged from 0.5 to 1.6 Hz.

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