Method for monitoring of the protein amino group changes during carbonylation

Carbonylation of the protein amino, guanidino and thiol groups is one of the important causes of vascular complications in diabetes. We developed a simple spectrophotometric method for monitoring of the changes in the protein amino group contents during carbonylation. The method is based on the reaction of amino group with p-benzoquinone in the slightly alkaline media. It was applied during carbonylation in vitro with methylglyoxal and in vivo in 13 patients with type 2 diabetes and 20 healthy persons. The method is simple, fast, precise (RSD in the range of 1.2–1.8%) and accurate (recovery about 100%). The content of amino groups in human serum albumin isolated from diabetics was significantly lower (p < 0.01) in comparison with a control group. The method developed is suitable for quantification of protein amino groups during in vitro carbonylation as well as for clinical practice.