Capillary electrophoresis for monitoring dityrosine and 3-bromotyrosine synthesis

Protein oxidation affects the structure of many amino acids. Variants of tyrosine are increasingly important in medical and food sciences. The synthesis of standards is essential for monitoring the disease state of patients with various illnesses and the quality of a number of food products. A method for monitoring standard synthesis of dityrosine and 3-bromotyrsoine from tyrosine using capillary electrophoresis (CE) is presented. Optimum separation was achieved using an isoelectric buffer consisting of 100 mM iminodiacetic acid (IDA) + 75 mM lauryl sulfobetaine (SB 3-12) + 0.02% hydroxypropyl methylcellulose (HPMC) in a 27 cm × 75 μm capillary at 22 kV and 45 °C. Using these conditions the tyrosine adducts could be easily separated in less than 4 min. The resolution of the CE method was similar to HPLC separations, but analysis time was distinctly shorter.