CAPILLARY ELECTROPHORESIS-MATRIX-ASSISTED LASER-DESORPTION IONIZATION MASS-SPECTROMETRY OF PROTEINS

An ''off-line'' combination of capillary electrophoresis (CE) with matrix-assisted laser-desorption mass spectrometry (MALDI-MS) has been developed for the structural characterization of CE-separated peptides and proteins. Using a sheath flow interface, similar to that developed for ''on-line'' CE-fast atom bombardment MS and CE-electrospray MS, an efficient sample isolation procedure has been developed which is applicable to bioorganic compounds in aqueous buffer solutions. This isolation procedure, with subsequent transfer to the MALDI-MS sample target, has been successfully used for the direct analysis of CE-separated proteins of M(r) up to 67 000, and a mixture of apolipoprotein AII monomer and homodimer, using sample amounts of less than 1 pmol.