The effect of succinylation on the properties of αs1-casein enriched protein

αs1-Casein was succinylated using different levels of succinic anhydride. The succinylation was monitored by measuring the unmodified lysine residues using an o-phthaldialdehyde method, by the change in mobility and staining intensity on SDS-PAGE gels or through mass spectrometry techniques. Succinylation markedly modified the zeta potential, shifting the pH versus zeta potential curve to lower pH as the succinylation level increased. The isoelectric pH was progressively decreased as the succinylation level was increased. Succinylation resulted in a progressive reduction in the apparent hydrophobicity of αs1-casein, which was a consequence of the increase in the negative charge of the proteins, resulting in a correlation between the hydrophobicity and the isoelectric pH. Compared to the native protein, succinylation of αs1-casein reduced the level of α-helix and increased the level of β-sheet secondary structural elements.