Analysis of recombinant and modified proteins by capillary zone electrophoresis coupled with electrospray ionization tandem mass spectrometry

A method for rapid characterization of recombinant and modified proteins wi th known sequences is described. The analytical system consists of a capill ary zone electrophoresis (CZE) instrument coupled to an electrospray ioniza tion ion trap tandem mass spectrometer via a sheath-flow interface. Followi ng the procedure consists of proteolytic fragmentation, CZE peptide separat ion, tandem mass spectrometry (MS-MS) analysis of separated peptides, seque nce database search and monitoring of the specific peptides, C 125 S mutate d interleukin 2 (S-125-IL2) and bovine p-casein were characterized as a mod el of recombinant protein and naturally modified protein, respectively. A t ryptic peptide mixture derived from the synthetic salmon calcitonin (s-CT) was also analyzed to test the performance of the system. Although a convent ional sheath-flow interface with much higher flow-rate compared to the micr ospray interface and nanospray interface was used, the proteins were identi fied at the low picomole level. (C) 1999 Elsevier Science BN. All rights re served.