Peptide purification by affinity chromatography based on alpha-ketoacyl group chemistry

Significant advances have been achieved in the fields of peptide/protein synthesis, permitting the preparation of large, complex molecules. Shortcomings, however, continue to exist in the area of peptide purification. This paper details some studies we undertook to develop a new strategy for peptide purification based on a reactivity of alpha-ketoacyl groups in peptides. The alpha-ketoacyl peptide was generated from N(epsilon)-acyl-lysyl-peptide in the solid phase via a transamination reaction using glyoxylic acid and nickel(II) ion. Cleavage of the alpha-ketoacyl group with o-phenylenediamine gave the target peptide in an acceptable yield and purity. We first carried out a careful step-by-step optimization of the purification conditions using a model peptide. The strategy was then used in the purification of a transmembrane peptide that could not be effectively purified using a conventional RP-HPLC system due to the strong hydrophobicity of the peptide and its high tendency to aggregate.