title: Quantitative 250 MHz proton magnetic resonance study of hydrogen-deuterium exchange. Angiotensin II hormone in trifluoroethanol.
abstract: Hydrogen-deuterium exchange kinetics of (Asn1-Val5) angiotensin II has been investigated by proton magnetic resonance at 250 MHz in deuterated trifluoroethanol, as an approach to the "in situ" hormone conformation. An interactive program was specially developed to perform the data analysis on a computer similar to those used for spectroscopic data acquisition. Nine exchange sites are evidenced and characterized by their individual kinetic parameters. Three of them are assigned to peptide NH hydrogens, and the six remaining to slowly exchanging side chain protons. At 11 degrees C, more than three peptide hydrogens, sterically hindered or involved in hydrogen bonds, do not exchange. These results corroborate previous circular dichroism and infrared investigations performed in the same solvent, and suggest a family of well-folded conformations, stabilized in trifluoroethanol by internal hydrogen bonds, involving both the backbone and the side chain hydrogens.
mesh_terms: D000804:Angiotensin II / Q000378:metabolism; D003201:Computers; D003903:Deuterium / Q000378:metabolism; D006728:Hormones; D006859:Hydrogen / Q000378:metabolism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared; D014270:Trifluoroethanol
chemical_list: D006728:Hormones; D000804:Angiotensin II; D014270:Trifluoroethanol; D006859:Hydrogen; D003903:Deuterium