查看文章

We report a fast and easy‐to‐use procedure that combines polyacrylamide gel electrophoresis with matrix assisted laser desorption/ionization‐time of flight‐mass spectrometry (MALDI‐TOF) and nanoelectrospray‐tandem mass spectrometry (nES‐MS/MS) analysis for the identification of casein components and defined phosphorylated sites. This methodology ensured identification of more than 30 phosphorylated proteins, five β‐, fifteen α_s1‐, ten α_s2‐, and four κ‐casein (CN) components, including nonallelic, differently phosphorylated, and glycosylated forms. The sugar motif covalently bound to κ‐CN was identified as chains, trisaccharide GalNAc, Gal, NeuGc, and tetrasaccharide 1GalNAc, 1Gal, 2NeuGc. Also identified was a biantennary chain made up of both chains of trisaccharide 1GalNAc, 1Gal, 1NeuGc, and tetrasaccharide 1GalNAc, 1Gal, 2NeuGc moiety on a single κ‐CN component. The phosphate group …