title: Fractionation of beta-lactoglobulin tryptic peptides by ampholyte-free isoelectric focusing.
abstract: Solutions of tryptic hydrolysate of bovine beta-lactoglobulin were fractionated by liquid-phase IEF in a preparative Rotofor cell at constant power for 2 h without ampholytes in order to identify interactions between peptides. The 20 peptide fractions collected were analyzed by capillary electrophoresis and SDS-PAGE under native, denaturing, and reducing conditions. The hydrolysate was shown to be composed mainly of acidic peptides (pI 2-5, 62%) of molecular mass below 6 kDa, and numerous disulfide bonds were detected. Purified peptides (beta-LG 15-20, 71-75, 76-82, and 84-91) were also focused individually and in mixtures and matched to components of the IEF fractions obtained from the tryptic hydrolysate of beta-LG. The separation of acidic (beta-LG 84-91) and basic (beta-LG 76-82) peptides was achieved by IEF, whereas uncharged peptides (beta-LG 15-20 and 71-75) were poorly separated due to their low electrophoretic mobility. Because no peptide-peptide interaction could be identified by IEF fractionation, it is suggested that electrical fields may decrease electrostatic interactions between charged peptides.
authors.affiliation: Centre de Recherche STELA, Pavillon Paul-Comtois, Université Laval, Québec, Canada G1K 7P4.
authors.forename: Paule Emilie
authors.initials: PE
authors.lastname: Groleau
authors.forename: Rafael
authors.initials: R
authors.lastname: Jimenez-Flores
authors.forename: Sylvie F
authors.initials: SF
authors.lastname: Gauthier
authors.forename: Yves
authors.initials: Y
authors.lastname: Pouliot
mesh_terms: D000818:Animals; D002021:Buffers; D002417:Cattle; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing / Q000379:methods; D007782:Lactoglobulins / Q000032:analysis* / Q000737:chemistry; D008894:Milk Proteins / Q000737:chemistry*; D008970:Molecular Weight; D011492:Protein Hydrolysates / Q000032:analysis* / Q000378:metabolism; D000067816:Whey Proteins
chemical_list: D002021:Buffers; D007782:Lactoglobulins; D008894:Milk Proteins; D011492:Protein Hydrolysates; D000067816:Whey Proteins