THE POTENTIAL OF PERTURBED ANGULAR-CORRELATION OF GAMMA-RAYS AS A TOOL FOR DYNAMIC STUDIES OF PEPTIDES PROTEINS

Four peptides and serum albumin have been derivatized with the bicyclic anydride of diethylenetriamine-pentaacetic acid. Procedures were developed to isolate the labelled species and determine the degree of derivatization. By using perturbed angular correlation of gamma-ray spectroscopy it is possible, through the determination of rotational correlation times, to decide whether labelled peptides interact with other molecules (receptors). In the case of the peptide cholecystokinin it is shown that the interaction between the peptide and its corresponding polyclonal antibody can be determined down to 1 pmol hormone. Experiments on In-111 and Cd-111m-labelled Gly-Trp showed that, where the Cd-111 PAC spectrum directly reflected the rotational motion of the molecule, the In-111 PAC spectrum was affected by the nuclear transitions to Cd-111m.