Molecular weight determination of recombinant interleukin 2 and interferon gamma by electrospray ionization mass spectroscopy.

The molecular weights of the recombinant proteins interleukin 2 and interferon gamma were determined by electrospray ionization (ESI) mass spectroscopy on the whole molecules. For interleukin 2 an average experimental mass of 15,549.4 u, was observed in excellent agreement with the theoretical average mass of 15,547.2 u. The mass observed for interferon gamma (16,908.4 u) agreed with the theoretical molecular weight of the monomeric species (16,907.3 u). By ESI mass spectrometry it was possible to determine the presence of proteins lacking one or two amino acids.