ANALYSIS OF PROTEIN-FRACTIONS BY MICROPREPARATIVE CAPILLARY ISOELECTRIC-FOCUSING AND MATRIX-ASSISTED LASER-DESORPTION TIME-OF-FLIGHT MASS-SPECTROMETRY

In this study, the use of capillary isoelectric focusing (cIEF) as a m icropreparative tool for protein analysis by matrix-assisted laser des orption time-of-flight mass spectrometry (MALDI-TOF-MS) is demonstrate d. A newly designed, automated, collection interface equipped with a f iber-optic UV detector and a sheath flow connection was employed for c ollection of protein fractions. Multiple fractions were collected duri ng a single cIEF run and further analyzed by MALDI-TOF-MS for mass ass ignment. The feasibility of the method was tested with a mixture of mo del proteins with different isoelectric points and molecular masses, a nd with variants of human hemoglobins differing in pI, but with neglig ible difference in M(r). Some practical considerations of the collecti on procedure and subsequent TOF analysis are presented.