MACROMOLECULE ANALYSIS BASED ON ELECTROPHORETIC MOBILITY IN AIR - GLOBULAR-PROTEINS

Globular proteins ranging in molecular mass from 5.7 to 669 kDa were s eparated and analyzed using an aerosol technique based on the electrop horetic mobility of singly-charged molecular ions in air. The ions wer e produced by electrospraying and drying 100-nm-diameter droplets of a Liquid suspension of the proteins, using ionized air to remove the dr oplet charge due to the spray process. The electrophoretic mobility wa s measured using a modified commercial continuous-flow differential mo bility analyzer operated near atmospheric pressure. An unmodified comm ercial condensation particle counter was used for detection. The conce ntrations analyzed ranged from 0.02 to 200 mu g of protein/mL of buffe r, with a liquid sample now rate of approximately 50 nL/min. Sampling time of 3 min was used for each complete distribution measured. The el ectrophoretic mobilities measured were determined entirely from air no w rates, apparatus geometry, and applied potentials. Results were expr essed as electrophoretic mobility equivalent diameters using a Millika n formula.