Preparation of Linear 217-bp DNA

DNA fragments containing 217-bp and Ava II cohesive ends were excised from purified pUC19 plasmids with AvaII restriction enzyme, and purified by size exclusion chromatography on a Sephacryl S-500 column (2 X 90 cm) equilibrated with 10 mM Tris, pH 7.5, 100 mM NaCl.

Fractions containing the 217-bp DNA target were pooled and concentrated using a Centricon-100 ultrafiltrator of 100,000 Da cutoff (Amicon, Inc., Beverly, MA).

DNA concentrations were determined from absorbance measurements at 260 nm (_{_260} = 13,000 M^-1 · cm^-1 · bp^-1).