The resulting mixture was
centrifuged for 10 min at 3697g. The supernatant was passed through
glass wool, stirred for 1 h at 4 C following the addition of PEG-8000 to
10% (w/v), and centrifuged at 1643g. The resulting pellet was resuspended
in 2 mL of sterile distilled water, and NaCl was added to a
concentration of 0.3 M, followed by one extraction with chloroform to
eliminate the PEG. The aqueous phase was recovered and the virus
protein concentration estimated using the Bradford method