SynopsisThe proton magnetic resonance spectrum of thyrotropin releasing factor (TRF) in solution in deuterium oxide and deuterated dimethylsulfoxide (DMSO-d6) has been analyzed. Two forms differing in cis-trans isomerism about the His-Pro peptide bond are observed. From the temperature dependence of chemical shift of the amide protons, it is concluded that TRF in DMSO-d6 does not contain intramolecular hydrogen bonds. Measurement of NH-C,H coupling constant provides an estimate of the histidine dihedral angle 4. Structural information about the histidine sidechain is deduced frcm C,H-CpH coupling constants and from the nonequivalence of the two prolyl &-protons. In DMSO-ds, there is evidence for a tautomeric equilibrium corresponding to an exchange of imidazole proton between the two nitrogen atoms N-6 and N-E. In water, the N-EH tautomer is found to be the predominant tautomeric form of the imidazole ring. These resultd in combination with energy calculation, vibrational analysis, and carbon nmr studies allow the determination of the conformation of TRF.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.