title: Isolation and characterization of an aggregating peptide from a tryptic hydrolysate of whey proteins.
abstract: Spontaneous precipitation of a peptide mixture has been observed during the concentration by reverse osmosis of a tryptic hydrolysate of whey protein. The precipitated material collected by centrifugation could not be solubilized by urea, mercaptoethanol, or sodium dodecyl sulfate. However, a complete solubilization of the aggregates was observed when the pH of the solution was lowered to 2.0. Analysis of the insoluble fraction has allowed the identification of beta-lactoglobulin (beta-lg) fragment 1-8 as the major peptide involved in the formation of aggregates. Peptide beta-lg f1-8 accounted for >94% of the peptide content in the precipitate washed twice with distilled water. The investigation of the secondary structure using circular dichroism evidenced that the peptide beta-lg f1-8 isolated from the flocculated peptide mixture is under random coil conformation at acidic and neutral pH and tends to adopt a beta-sheet conformation at basic pH. The findings of this study provide evidence that peptide beta-lg f1-8 forms aggregates via an efficient self-assembly process.
authors.affiliation: STELA Dairy Research Center, Institute of Nutraceuticals and Functional Foods (INAF), Université Laval, Quebec City, Quebec, Canada G1V 0A6. Yves.Pouliot@inaf.ulaval.ca
authors.forename: Yves
authors.initials: Y
authors.lastname: Pouliot
authors.forename: Marie-Michèle
authors.initials: MM
authors.lastname: Guy
authors.forename: Mélanie
authors.initials: M
authors.lastname: Tremblay
authors.forename: Anne-Cécile
authors.initials: AC
authors.lastname: Gaonac'h
authors.forename: Bertrand P
authors.initials: BP
authors.lastname: Chay Pak Ting
authors.forename: Sylvie F
authors.initials: SF
authors.lastname: Gauthier
authors.forename: Normand
authors.initials: N
authors.lastname: Voyer
mesh_terms: D011232:Chemical Precipitation; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007782:Lactoglobulins / Q000737:chemistry*; D008894:Milk Proteins / Q000737:chemistry* / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism; D017433:Protein Structure, Secondary; D012995:Solubility; D014357:Trypsin / Q000378:metabolism*
chemical_list: D007782:Lactoglobulins; D008894:Milk Proteins; D010446:Peptide Fragments; D014357:Trypsin