Isolation and purification of serum and interfacial peptides of a trypsinolyzed beta-lactoglobulin oil-in-water emulsion

Information on the conformation of proteins adsorbed to an oil-water interf ace is usually determined by following the time course of enzymatic hydroly sis of the protein in an oil-in-water emulsion. Unlike previous works repor ted in the literature, the research presented in this paper provides inform ation on which peptides are actually in contact with the lipid bilayer (int erfacial peptides) and those segments that project into the aqueous phase ( serum peptides). In order to achieve this classification of peptides, we pr esent a method to separate serum peptides from interfacial peptides by init ial centrifugation steps followed by reversed-phase high-performance liquid chromatography. The effectiveness of the method was ascertained by perform ing proteolysis on beta-lactoglobulin adsorbed to an oil-water interface in a soybean oil-water emulsion. It was found that more peptides are qualitat ively and quantitatively found adsorbed to the oil-water interface as compa red to peptides released into the serum, (C) 2000 Elsevier Science B.V. All nights reserved.