DOUBLE-STRANDED DNA ANALYSIS BY CAPILLARY ELECTROPHORESIS WITH LASER-INDUCED FLUORESCENCE USING ETHIDIUM-BROMIDE AS AN INTERCALATOR

We have developed a rapid and sensitive method to analyze double-stran ded DNA by capillary electrophoresis equipped with a laser-induced flu orescence detector. Using ethidium bromide as an intercalator in polya crylamide gel-filled capillaries along with a green He/Ne laser source (excitation: 543 nm; emission: 600 nm), we found the detection sensit ivity for a single DNA-ethidium bromide complex was in the picogram le vel with a resolution of one base pair separation between two DNA frag ments. In the case of the separation of a phi X174 DNA-HaeIII digest, sizes from 72 to 1353 bp were well resolved within 12 min. For the ana lysis of PCR-amplified DNA, low levels of amplified DNA fragments coul d be detected that could not be visualized in agarose gel after standa rd ethidium bromide staining. Considering the high resolving power and sensitivity, we believe that this method can be a useful tool for the analysis of double-stranded DNA especially for PCR-amplified DNA frag ments.