Electrophoretically mediated microanalysis of beta-galactosidase on microchips

Electrophoretically mediated microanalysis (EMMA) is a method of accomplish ing chemical analyses, typically in an open-tubular capillary, due to the d ifference in the electrophoretic mobility between the particular reagents. This work reports on combining this technique onto microfabricated systems. Two methods of this technique were applied, constant potential and zero po tential EMMA onto chips. A dosage response curve was run using this constan t potential mode that resulted in a linear response over three orders of su bstrate concentration magnitude. The chemical system used here is beta -gal actosidase (beta -Gal) as the enzyme and fluorescein mono-beta -D-galactopy ranoside (FMG) as the substrate. The zero potential mode was used to amplif y product turnover using various incubation times. Using this technique and a 10 min incubation, similar to 40 000 enzyme molecules could be detected. The zero potential mode is also used in conjunction with an internal stand ard to show how one can quantitate using this method. The power and ease of utility of this technique is described.