Two-dimensional direct-reading fluorescence spectrograph for DNA sequencing by capillary array electrophoresis

We report a compact, two-dimensional direct-reading fluorescence spectrogra ph and demonstrate its application to DNA sequencing by capillary away elec trophoresis. The detection cuvette is based on sheath flow, wherein the cap illaries terminate in a two-dimensional array in a fluid-filled chamber tha t is pressurized with buffer. A thin metal plate is located downstream from the capillaries. This barrier plate has an array of holes that precisely m atches the location of the capillaries. Buffer flows through the holes, dra wing analyte from the capillaries in a well-defined array of thin filaments . Fluorescence is excited in the upper chamber with an elliptically shaped laser beam. The bottom chamber is sealed with a glass window and drained fr om die side. Fluorescence is detected by imaging the illuminated sample str eams through the holes in the barrier plate. A prism is used to disperse fl uorescence from each sample across a CCD camera so that the emission, spect rum is monitored simultaneously from each capillary. The instrument is demo nstrated in a 32-capillary configuration but can be scaled to several thous and capillaries.