Purification and identification of alpha(s-1) and beta-caseins from asses milk

Recent clinical studies have demonstrated that feeding with asses milk is a safe and valid treatment for infants affected by protein intolerance to dairy cows milk . In fact, the composition of asses milk is similar to humans milk, especially concerning the lipid and protein fraction contents. In the present study αS1- and β-caseins were purified from asses milk by gel filtration chromatography followed by anion exchange chromatography on HPLC. The obtained caseins were characterized by SDS-PAGE and, after blotting on a PVDF membrane, were identified by N-terminal sequencing. Through chromatographic techniques it was possible to separate and identify αS1-caseins having the N-terminal sequence RPKLPHRXPE and molecular weights of 30.9 and 33.0 kDa, and β-caseins, having the N-terminal sequence REKEELNVS and molecular weights of 34.0 and 35.4 kDa. It was not possible to determine the presence of other types of caseins such as1- and κ-that have been found in mares milk.