Investigation of the Structure of Angiotensin II Using ¹³C Nuclear‐Magnetic‐Resonance Spectra

Abstract

Using the fast Fourier transform technique it has been possible to get readable natural‐abundance carbon‐13 nuclear magnetic resonance spectra of some oligopeptides, in particular the octapeptide angiotensin II. An assignment of the carbon‐13 resonances to the distinct carbons of the peptides has been made by comparison of the resonances with the corresponding resonances of free amino acids. From the pH dependence of the chemical shifts of the carbon‐13 resonances of the octapeptide angiotensin II, pK values can be derived for titratable groups of this hormone. These pK values as well as the shape of the titration curves are interpreted in terms of intramolecular interactions.