DEOXYRIBONUCLEASE TREATMENT IMPROVES THE HOMOGENEITY OF SINGLE-STRANDED-DNA PREPARATIONS

The isolation of single-stranded (ss) phagemid DNA using standard prot ocols often results in impure preparations, which contain undesirable quantities of chromosomal and/or double-stranded (ds) phagemid DNA. He re we report a simple and efficient method for elimination of virtuall y all dsDNA by incubation of phagemid viral particles with deoxyribonu clease I. In addition to analyzing the ratio of linear-to-circular top ological forms of ssDNA after deoxyribonuclease I treatment, we verifi ed that no decrease in transformation efficiency occurred and demonstr ated that ssDNA molecules covered by capsid proteins remained intact f ollowing such treatment.