Detection of specific noncovalent protein-fullerenols complexes by matrix-assisted laser desorption ionization mass spectrometry

Matrix-assisted laser desorption ionization (MALDI) mass spectrometry is di fficult for the characterization of noncovalent complexes hitherto because of the limitations in acidic matrix, sample preparation, laser-induced poly merization and adduct formation with matrix. Under our experimental conditi ons, sinapinic acid is used as a matrix, the specific noncovalent interacti ons of protein with fullerenols were observed by MALDI mass spectrometry. S ome mass spectrometric features, such as mass shifts, broad adduct peaks an d stoichiometries, showed that the specific non-covalent complexes between protein and fullerenols have been formed at a ratio of 1 : 4 for hemoglobin -fullerenols or 1 : 1 for myoglobin-fullerenols. The results implied that f ullereneols could be used to protect partly hemoglobin from decomposition i n acidic media, and therefore, it is possible to realize the molecular weig ht determination of a quaternary protein by MALDI mass spectrometry via the addition of specific organic compound in the matrix.