English Abstract Recently, two mass spectrometric techniques have been
introduced for the accurate determination of the molecular weight of
proteins and peptides, namely Plasma Desorption-Mass Spectrometry (PD-MS)
and Electro Spray- Mass Spectrometry (ES-MS). In this study the
applicability of these techniques to laboratory samples has been tested.
Measurements have been performed in the framework of the study on the
stability of monoclonal antibodies (mabs) like IgG2a. Because the molecular
weight of IgG2a exceeds the mass range of the PD-MS instrument, the test
compound has been cleaved into Fab and Fc fragments with expected molecular
weights after reduction of approximately 25,000 Dalton. The Fab and Fc
fragments have been separated, reduced, solved in 0.01% sodium azide
solution, and were offered for analysis as two separate samples. With the
ES-MS technique in both samples two compounds have been detected with
molecular weights in the range of 24,000 to 26,000 Dalton. The molecular
weights were determined with an accuracy better than 0.02%. The sample
amount used was 100-200 pmol. With the PD-MS technique no interpretable
spectra have been obtained.
