The molecular weights of plasma proteins from healthy subjects and from patients with well-or badly-controlled diabetes mellitus have been determined by use of a matrix-assisted laser desorption ionization method, representing a highly accurate technique for the determination of the molecular weight of large biomolecules. Using this approach, different molecular weights of human serum albumin have been found for healthy (66,572-66,694 dalton) and diabetic (66,785-68,959 dalton) subjects. Such differences can be rationalized as being due to the different number of glucose molecules condensed on the protein and/or their further oxidation products; in the case of our diabetic patients this number is in the range of 1.4-14.8. The data show the high validity and specificity of the technique, which allows us to evaluate, without any protein degradation procedure, the number of glucose molecules condensed on a specific protein and ascertain the relationship of this number to the physiopathogenetic conditions of the subjects studied.

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The products arising from the reactions of ribonuclease with glucose or fructose have been studied by means of matrix-assisted laser desorption/ionization mass spectrometry. The reactions have been carried out at physiological pH, with two different sugar concentrations and different incubation times. A maximum increase in molecular weight, corresponding to 485 Da, was found in the case of ribonuclease incubated with 0.25 M fructose for 6 days. Furthermore clear differences have been found in the reactivity of glucose and fructose; in particular, while glucose reacts faster than fructose in the early stage of the glycation, the rearrangements of the Amadori adducts are favoured using fructose as reagent sugar.

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.

Pyrolysis/gas chromatography/mass spectrometry was applied to the study of products arising from the interaction between glucose and poly-L-lysine. The comparison of pyrograms of control poly-L-lysine and glycated poly-Llysine ied to the identitication of six different compounds, four of which were furan derivatives that can be considered as markers for advanced glycation processes.