Stability of glyoxal- and methylglyoxal-modified hemoglobin on dried blood spot cards as analyzed by nanoflow liquid chromatography tandem mass spectrometry.

Blood sampling by the dried blood spot (DBS) technique has become commonly applied in newborn screening. It is often used for analysis of small molecules, such as metabolites. Recently, DBS sampling has been applied for quantification of post-translational protein modifications. Glyoxal and methylglyoxal are two simple oxoaldehydes released from glycated proteins in the Maillard reaction. They are widely distributed in the environment (e.g. cigarette smoke) and found in foods and beverages. Glyoxal and methylglyoxal are shown to react with biomolecules including DNA and proteins. In this laboratory, we previously identified the sites of modification by these two oxoaldehydes in human hemoglobin and found that the extents of modification at certain sites of lysine and arginine residues are significantly higher in type 2 diabetes mellitus patients than in nondiabetic individuals. In this study, we examine the stability of these modifications of hemoglobin stored on DBS cards at room temperature or 4 °C in the ambient air. After hemoglobin was extracted from the DBS cards, it was digested by trypsin and analyzed by nanoflow liquid chromatography coupled with nanospray ionization tandem mass spectrometry. The results show that the extents of all these PTMs are stable within 14 and 21 days when stored on DBS at room temperature and at 4 °C, respectively. Extraction of globin from DBS cards is mostly advantageous for hemolytic blood samples. This assay is sensitive as only a quarter of a DBS card containing ca. 12 μL of blood is required. Thus, it is practically useful to measure the extents of glyoxal- and methylglyoxal-induced hemoglobin modifications from DBS cards.