Volume 78, No. 8, p. 4029-4036, 2004. Page 4030: We have recently recognized an inadvertent error in the Materials and Methods section. The centrifuge rotors and g forces were described incorrectly and should read as follows.
Buoyant density gradient analysis of lentiviral vectors. The supernatants were harvested and filtered through a 0.45-μm syringe filter. The recombinant virus was first concentrated by layering a 10-ml sample in tissue culture media onto 2.5 ml of Optiprep (Iodixanol) (60%) solution (Invitrogen, Carlsbad, Calif.) and centrifuging it at 53,000 × g for 1 h in a Sorvall TH-641 rotor (Kendro, Newtown, Conn.). The top 7.5 ml of supernatant was removed, and the remaining solution was mixed uniformly to achieve a final concentration of 30% Optiprep in a 5-ml final volume. The gradient was formed by centrifugation at 363,000 × g for 3.5 h with a Beckman NVT-100 rotor.
This information does not alter the conclusions of the paper.