Kinetics of Angiotensin I alteration of conformation on different hydrophobic interaction chromatographic surfaces

In the present study, Angiotensin I (Ang I) will be used as model peptide to assess on-column alteration of conformation phenomena. Adsorptive behavior of Ang I on various commercial hydrophobic interaction surfaces (Butyl, Octyl and Phenyl – Sepharose), under different conditions, was investigated. In order to calculate the cis–trans isomerization rate constants of Ang I on the stationary phaseʹs surface, the first and second moments of the proline peptide elution profiles were determined. The activation energies for the isomerization process on Phenyl and Butyl Sepharose were also calculated. Results suggest that the stationary phase catalyzes Ang I isomerization and that catalysis is dependent on hydrophobic interaction ligand nature.