CAPILLARY ELECTROPHORESIS ELECTROSPRAY-IONIZATION FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE MASS-SPECTROMETRY FOR DIRECT ANALYSIS OF CELLULAR PROTEINS

The combination of capillary electrophoresis (CE) with electrospray io nization (ESI) mass spectrometry has proven to be broadly applicable t o a wide range of biologically important compounds, When combined with Fourier transform ion cyclotron resonance (FTICR) mass spectrometry, the combined method, in addition to high-resolution separations, affor ds high-resolution precision mass measurements for analytes separated from complex mixtures. Direct chemical analysis of single cells has re ceived considerable attention in recent years; the single cell approac h provides a major step toward answering important questions in the fi eld of cellular biochemistry. In this work we present preliminary resu lts which demonstrate the feasibility of using the CE-ESI-FTICR combin ation as a high-performance detection scheme for the analysis of cellu lar proteins acquired. directly from small populations (i.e., 5-10) of intact living cells. The human erythrocyte was chosen as a model syst em owing to its availability, relatively homogeneous composition, and thorough documentation of contents by previous researchers. In this wo rk we demonstrate the on-line acquisition of high-resolution mass spec tra (average resolution greater than or equal to 45 000 fwhm) of both the alpha and the beta chains of hemoglobin acquired from the injectio n of 10 human erythrocytes (corresponding to 4.5 fmol of hemoglobin). Given the extremely small volume of the human erythrocyte (typically 8 7 fL/cell), the techniques implemented here should also be adaptable t o the study of larger mammalian cell systems.