A simple method for the preparation of single-stranded polydeoxynucleotides of desired length.

A method for the preparation of homogeneous, single-stranded polydeoxynucleotides of desired length up to 800 bases is described. The procedure entails 1) generation of double-stranded DNA of desired length by PCR using a pair of primers of which one is biotinylated and the other is either unlabeled or fluorescently labeled, 2) isolation of PCR products by agarose slab gel electrophoresis, 3) recovery of desired product by electroelution, 4) binding of the product to streptavidin-coated magnetic beads and is followed by 5) duplex denaturation and removal of the unbound single strand that is either unlabeled or fluorescently labeled. Final product characteristics were determined by capillary gel electrophoresis with fluorescence detection. Up to microgram quantities of homogeneous single-stranded DNA of a desired length were obtained. These can be used as single-stranded size standards in capillary gel electrophoresis experiments as well as in other techniques requiring such standards.