sentence: Supercoiled pGEM-9Zf ( − ) ( 300 ng ) served as target DNA in the assays with RU5 and RU5 donors.Integration reactions were stopped by addition of 0.5 % SDS and 25 mM EDTA and deproteinized by digestion with 30 μ g proteinase K ( Roche Applied Science ) for 45 – 60 min at 37 ° C followed by ethanol precipitation .