Attomole Protein Characterization by Capillary Electrophoresis-Mass Spectrometry

Science  30 Aug 1996:
Vol. 273, Issue 5279, pp. 1199-1202
DOI: 10.1126/science.273.5279.1199


Electrospray ionization with an ultralow flow rate (≤4 nanoliters per minute) was used to directly couple capillary electrophoresis with tandem mass spectrometry for the analysis and identification of biomolecules in mixtures. A Fourier transform mass spectrometer provided full spectra (>30 kilodaltons) at a resolving power of ≈60,000 for injections of 0.7 × 10−18 to 3 × 10−18 mole of 8- to 29-kilodalton proteins with errors of <1 dalton in molecular mass. Using a crude isolate from human blood, a value of 28,780.6 daltons (calculated, 28,780.4 daltons) was measured for carbonic anhydrase, representing 1 percent by weight of the protein in a single red blood cell. Dissociation of molecular ions from 9 × 10−18 mole of carbonic anhydrase gave nine sequence-specific fragment ions, more data than required for unique retrieval of this enzyme from the protein database.