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A new method, based on matrix-assisted laser desorption/ionization (MALDI) measurements, has been developed for the evaluation of the glycation level of globins, a relevant parameter for diabetes control. It shows high levels of reproducibility and specificity, allowing the different glycated and glyco-oxidized products of both alpha- and beta-globins to be distinguished. Such specificity is reflected in its possible diagnostic use not only for the control of diabetes, but also for the occurrence of 'oxidative stress'. The comparison, for the same samples, of the obtained MALDI data with the related HbA1c values, determined by a high performance liquid chromatographic method, allowed it to be established that HbA1c percentages are not, as usually retained, related to the simply glycated beta-globin, but to the whole pool of glycated and glyco-oxidized alpha- and beta-globins.

The non-enzymatic reactions between glucose or fructose with lysozyme, performed under pseudo-physiological conditions, have been studied by means of matrix-assisted laser desorption/ionization mass spectrometry. Phosphate buffer at concentrations of 0.05, 0.2 and 0.5 M has been employed. The formation of glycated proteins as well as of cross-linking products has been always observed. In the case of glucose, high phosphate buffer concentrations affect the glycation kinetics and promote the formation of cross-linking products. With fructose, such influence is moderate, the reaction kinetics being mainly influenced by the higher reactivity of the sugar.