Water-protein hydrogen exchange in the micro-crystalline protein Crh as observed by solid state NMR spectroscopy
We report site-resolved observation of hydrogen exchange in the micro-crystalline protein Crh. Our approach is based on the use of proton T-2(')-selective H-1-C-13-C-13 correlation spectra for site-specific assignments of carbons nearby labile protein protons. We compare the proton T-2(') selective scheme to frequency selective water observation in deuterated proteins, and discuss the impacts of deuteration on C-13 linewidths in Crh. We observe that in micro-crystalline proteins, solvent accessible hydroxyl and amino protons show comparable exchange rates with water protons as for proteins in solution, and that structural constraints, such as hydrogen bonding or solvent accessibility, more significantly reduce exchange rates.