MICROFABRICATED SILICON MIXERS FOR SUBMILLISECOND QUENCH-FLOW ANALYSIS

Elucidation of fast chemical reactions such as protein folding require s resolution on a submillisecond linne scale. However, most quench-flo w and stop-flow techniques only allow chemical processes to be studied after a few milliseconds have elapsed. in order to shorten the minimu m observation time for quench-flow experiments, we designed a miniatur ized mixer assembly, Two ''T'' mixers connected by a channel are etche d into a 1 cm x 1 cm silicon chip which is interfaced with a commercia lly available quench-flow instrument. Decreasing the volume of the mix ing chambers and the distance between them results in an instrument wi th, greatly reduced dead times. As a test of submillisecond measuremen ts, rye studied the basic hydrolysis of phenyl chloroacetate, This rea ction proceeds with a second-order rate constant, k = 430 M-1 s(-1), a nd shows pseudo-first-order kinetics at high hydroxide concentrations, The chemical reaction data demonstrate that the silicon device is cap able of initiating and quenching chemical reactions in time intervals as short as 110 mu s. The performance of these mixers was further conf irmed by visualization using acid-base indicators.