title: A novel LC-MS application to investigate oxidation of peptides isolated from β-lactoglobulin.
abstract: Oxidation of β-lactoglobulin (β-Lg), a typical milk whey protein, was investigated by oxidizing its three tryptic peptides after separation and fractionation by preparative HPLC. Oxidation was performed with H2O2 and Fe(3+) in piperazine-1,4-bis(2-ethanesulfonic acid) (PIPES) buffer containing ascorbic acid, by keeping the samples in an oven of +37 °C for 14 days. Changes in the oxidized peptides were then analyzed with LC-ESI-QIT-MS. The peptides chosen were Ala-Leu-Pro-Met-His-Ile-Arg (ALPMHIR), Leu-Ile-Val-Thr-Gln-Thr-Met-Lys (LIVTQTMK) and Val-Leu-Val-Leu-Asp-Thr-Asp-Tyr-Lys (VLVLDTDYK), all containing amino acids of oxidative interest. Especially methionine (M) was prone to oxidize as well as dioxidize, along with tyrosine (Y), histidine (H) and/or proline (P). The ions m/z 854 [ALPMHIR + O], m/z 950 [LIVTQTMK + O] and m/z 966 [LIVTQTMK + 2O] are considered very promising indicators of β-Lg oxidation. Consequently, this study proposes a novel approach in peptide oxidation research through monitoring the oxidation markers identified with the LC-MS(n).
authors.affiliation: Department of Food and Environmental Sciences, Division of Food Chemistry, P.O. Box 27, FI-00014 University of Helsinki, Finland.
authors.forename: Tuuli
authors.initials: T
authors.lastname: Koivumäki
authors.forename: Göker
authors.initials: G
authors.lastname: Gürbüz
authors.forename: Marjo
authors.initials: M
authors.lastname: Poutanen
authors.forename: Marina
authors.initials: M
authors.lastname: Heinonen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006861:Hydrogen Peroxide / Q000737:chemistry; D007782:Lactoglobulins / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010449:Peptide Mapping; D010455:Peptides / Q000737:chemistry*
chemical_list: D007782:Lactoglobulins; D010455:Peptides; D006861:Hydrogen Peroxide