Non-enzymatic posttranslational modifications of bovine serum albumin by oxo-compounds investigated by chromatographic and electrophoretic methods

Non-enzymatic posttranslational modifications of bovine serum albumin (BSA) by oxo-compounds, particularly glucose, ribose, glyoxal and glutardialdehyde, have been investigated using a set of modern chromatographic and electrophoretic separation methods. High-performance liquid chromatography (HPLC) alternatively with UV spectrophotometric (diode array) or mass spectrometric (MS) detection, polyacrylamide gel electrophoresis (PAGE) with Coomassie brilliant blue staining detection, and capillary zone electrophoresis (CZE) with UV spectrophotometric detection have been employed for the investigation of the chemical and structural changes of BSA caused by its reaction with the above oxo-compounds exhibiting different degree of reactivity. The extent of modifications was found to be dependent on the nature of the oxo-compound used and progressed in the glucose < ribose < glyoxal < glutaraldehyde order. With the aid of HPLC/UV/MS and CZE/UV tryptic peptide mapping and amino acid analysis of both unmodified and modified BSA it was revealed that the mildest modification resulted from the reaction of BSA with glucose, in this case presumably only monofunctional derivatives have arisen, whereas the most intensive modifications were found after BSA reaction with glutardialdehyde, which resulted in high degree of both inter- and intra-molecular cross-linking, due to which no unmodified peptides were detected after tryptic cleavage of BSA modified by this agent.