Determination of phosphorylation degrees in caseins by on-line gel electrophoresis coupled to ICP-SFMS

Abstract

The determination of the phosphorylation degree of proteins is essential in many biochemical fields. Besides mass spectrometric techniques elucidating the protein structure, ICP-MS has entered this research area as it provides excellent quantification capabilities. In this work the separation of the proteins has been carried out by gel electrophoresis on-line coupled to an ICP equipped with a double-focusing sector field-MS (ELEMENT 2). Based on the simultaneous detection of ³²S⁺ and ³¹P⁺, this work presents an alternative approach to determining the phosphorylation degree of caseins. For the example of α- and β-casein the results obtained were in excellent agreement with the expected values, and therefore the described method might be very useful and serve as an alternative in the analysis of phosphorylated proteins.