Determination of PyPuPu (PyPuPy) intermolecular triple-stranded DNA by capillary electrophoresis

The PyPuPu and PyPuPy intermolecular triple-stranded DNA (tsDNA) can be determined more easily by capillary electrophoresis (CE) than by traditional methods. The tsDNA and its component compounds can be well separated by using a sieving matrix of 1.0% hydroxypropylmethylcellulose (HPMC) containing 2.5 mM magnesium ions. Such factors as buffer pH, the concentration of triplex-forming oligonucleotide (TFO), temperature, and the concentration of magnesium cation in the formation and stabilization of triple-stranded helices have been studied with capillary electrophoresis. The triplex cannot be formed when the buffer pH is lower than 4.0. When the concentration of TFO is four times higher than that of dsDNA, all of the dsDNA molecules can be associated. The limit of capillary electrophoresis detection with good reproducibility is 0.5-1 nM (S/N = 3). The CE analysis of short tsDNA takes only 40 min, whereas gel electrophoresis needs at least 5 h. (C) 2000 Academic Press.