Table II

Molecular mass-based identification of 2D gel-eluted κ-casein isoforms

Spot numberTheoretical molecular massa (Da)Experimental molecular mass (Da)Protein identificationPost-translational modification
119039.419039κ-Casein B
219119.419120κ-Casein B1 Phosphorylation
319151.419151κ-Casein A1 Phosphorylation
419151.419151κ-Casein A1 Phosphorylation
519151.419151κ-Casein A1 Phosphorylation 2
19231.419231κ-Casein APhosphorylation
620099NDbND
71865218653β-Lactoglobulin A
81856618563β-Lactoglobulin B,W
1856518563β-Lactoglobulin D
  • a Theoretical molecular masses were calculated according to the sequence of the variants and considering both the known post-translational modifications (i.e. removal of the signal peptide 1–22 and cyclisation of Glu22 for κ-casein, removal of signal peptide 1–16 for β-lactoglobulin) and the carbamidomethylation of the cysteine residues (2 for κ-casein and 5 for β-lactoglobulin).

  • b ND, not determined at this stage.