SEPARATION OF SMALL CATIONIC BIOACTIVE PEPTIDES BY STRONG ION-EXCHANGE CHROMATOGRAPHY

The high resolving power of a Hyper D cation-exchange column was evalu ated to achieve the separation of small cationic bioactive peptides de rived from tryptic digest of K-casein: MAIPPK (pI=9.9), MAIPPKK (pI=10 .5), KNQDK (pI=9.6) and NQDK (pI=6.35). The influence of pH (1.5-6), g radient slope (2-10 mM sodium chloride/min) and elution of the mixture under isocratic conditions was investigated. Although their physico-c hemical properties are very similar, these four peptides were readily resolved with an excellent selectivity and recovery. The selectivity o f the exchanger was also expressed toward peptides of the same net pos itive charge; the most hydrophilic peptide always eluted last. It was also shown that the elution order of these molecules depends on pH. Fr om the observed retention limes and the elution order, we have establi shed a simple approach to linearization of peptide retention behaviour on the S-Hyper D support.