FIG. 9.

Assessment of core protein envelopment by membrane protection assay. Electroporated cells were harvested at 72 h postelectroporation, and a membrane protection assay was performed as described in Materials and Methods. Postnuclear fractions were treated with 10 μg/ml proteinase K (PK) in the presence or absence of Triton X-100 (Tx-100) on ice for 1 h (top panel). The density of bands corresponding to the core proteins in each treatment was scanned and quantified. The percentages of core protein levels detected in samples treated with PK alone or with Triton X-100 and PK relative to the untreated sample were determined. A representative graph of experiments from duplicate electroporations with means and standard errors of the means is shown (bottom panel).