15N Solid-State NMR as a Probe of Flavin H-Bonding
journal contributionposted on 23.06.2011, 00:00 authored by Dongtao Cui, Ronald L. Koder, P. Leslie Dutton, Anne-Frances Miller
Flavins mediate a wide variety of chemical reactions in biology. To learn how one cofactor can be made to execute different reactions in different enzymes, we are developing solid-state NMR (SSNMR) to probe the flavin electronic structure, via the 15N chemical shift tensor principal values (δii). We find that SSNMR has superior responsiveness to H-bonds, compared to solution NMR. H-bonding to a model of the flavodoxin active site produced an increase of 10 ppm in the δ11 of N5, although none of the H-bonds directly engage N5, and solution NMR detected only a 4 ppm increase in the isotropic chemical shift (δiso). Moreover SSNMR responded differently to different H-bonding environments, as H-bonding with water caused δ11 to decrease by 6 ppm, whereas δiso increased by less than 1 ppm. Our density functional theoretical (DFT) calculations reproduce the observations, validating the use of computed electronic structures to understand how H-bonds modulate the flavin’s reactivity.