MULTIPLE SHEATH-FLOW GEL CAPILLARY-ARRAY ELECTROPHORESIS FOR MULTICOLOR FLUORESCENT DNA DETECTION

Gel capillary-array electrophoresis has been developed to achieve a high-sensitivity and high-throughput DNA analysis using real-time fluorescence detection. To eliminate excitation light scattering at the capillary surfaces and to irradiate all the migration tracks simultaneously, the capillary tubes were removed from the irradiated region. DNA fragments were eluted from the gel capillaries and flowed into the lower open capillaries. Multiple sheath flows of buffer solution around all the capillaries were produced to prevent DNA band diffusion in the gel-free irradiated region. The fluorescence image was detected with a two-dimensional detector coupled with an image-splitting prism having four color filters. As the background fluorescence from the sheath-flow region was very small, the minimum detectable concentration of fluorophore-labeled DNA was 10(-13) M in one-color mode (Texas Red was used), and it was 2 x 10(-12) M in four-color mode (fluorophores from Applied Biosystems were used). The experiment was carried out with the 20 capillaries and the base reading speed of 200 bases/h. However, it is easy to increase the number of capillaries and the electrophoresis speed to achieve very high throughput DNA analysis.