LIMITED ENZYMATIC DIGESTION FOR THE DETERMINATION OF THE QUANTITIES OF MINOR DIASTEREOMERIC IMPURITIES IN PREPARATIONS OF RMP-7, A PEPTIDE-CONTAINING A REDUCED PEPTIDE-BOND

RMP-7 is a bradykinin analogue containing all ''L'' amino acids and a reduced dipeptide bond between amino acids eight and nine. This reduce d dipeptide bond [4-Me-Tyr-Psi(CH2NH)-Arg] is created under synthetic conditions which could result in inversions of the chiral centers of e ither 4-Me-Tyr or Arg. Stereoisomers of RMP-7 would be expected to hav e altered biological specificity. Current chromatographic methods are not sufficiently sensitive to distinguish the anticipated stereoisomer ic variants of the intact molecule. Therefore we have devised an analy tical method based on limited enzymatic digestion of the compound foll owed by reversed-phase HPLC analysis of the peptide fragments. Using t his method we have been able to carry out precise and reliable quantit ative analysis of the stereoisomeric content of different batches of p eptide prepared for biological testing.