~16ug of Qiagen plasmid mini kit purified recombinant pAdEasy DNA was digested by pacI in 20ul final volume. We used this one (@4ug/well in a 6-well plate) for transfection into 293 cells using agilent ViraPack kit (cat.no.200488). Followed every procedure but no success. Even nucleofection method failed. What may be the reason? Will some amount of intact DNA interfere in transfection? I appreciate sharing your experience in troubleshooting.