FIG. 2.

DNA content of Optiprep-purified HPV16 capsids. Nuclease-resistant DNA was extracted from Optiprep-fractionated capsids subjected to prior incubation at 37°C for the time shown. During the extraction, the samples were spiked with 0.5 ng of a 1-kb DNA marker fragment to monitor recovery. The purified DNA samples were digested with BglII, separated on an agarose gel, and stained with SYBR Green I. It was necessary to dilute the sample recovered from the material incubated for 24 h in order to compare it to the 1- and 4-h samples. In the chart at the bottom of the figure, the total titer of the starting crude cell lysate is compared to the titer recovered in the fractionated material. Markers (annotated in kilobase pairs) are shown in the far left lane.