Determination of the loading values for high levels of drugs and sugars conjugated to proteins by matrix‐assisted ultraviolet laser desorption/ionization mass spectrometry

The loading values of high levels of anti-cancer drugs and sugars conjugated to human serum albumin were determined by matrix-assisted ultraviolet (UV) laser desorption/ionization mass spectrometry. The values were compared with those obtained by UV spectrometry, radioactivity labeling or by chemical analysis, and were found to be consistent. The matrix-assisted UV laser desorption/ionization method has been demonstrated to be a routine and reliable method for obtaining high loading values and therefore was applied to the determination of the loading of two experimental drugs, for treating AIDS and septic shock, respectively, when conjugated to bovine serum albumin, which could not be routinely determined by UV spectrometry since the chromophores of the drugs and protein overlap.