A study of elastase peptides from bovine white matter proteolipid

Bovine white matter proteolipid has been digested with elastase in the presence of deoxycholate. After acidification, the digest was separated into an acid-soluble and an acid-insoluble fraction. The acid-insoluble fraction was enriched in nonpolar amino acids and, by a combination of solvent fractionation and chromatography, a fraction was obtained which consisted of a mixture of two peptides with a molecular weight of approximately 4000 daltons. The acid-soluble peptides were separated by molecular sieve, ion exchange and high performance liquid chromatography (HPLC) in the reverse phase mode. The purified peptides were smaller than expected on the basis of their elution position from a molecular sieve column, suggesting they were in an aggregated state during the initial chromatography. Reverse phase HPLC was shown to be useful for fingerprinting these peptide mixtures. The data demonstrate the difficulties associated with the study of this proteolipid and emphasize the tendency of both the protein and the peptides derived from it to aggregate.