Electrophoresis 25 mg of virus preparations were separated on 10-20% Novex tricine gels (Invitrogen) according to the manufacturer's instructions, at 125 V for 2 hr at room temperature in the SureLock XCell minicell (Invitrogen). Gels were fixed for 30 min in 100 ml of a solution containing 50% methanol and 7% acetic acid. After 30 min, the fixing solution was replaced with fresh fixing solution. The gels were stained overnight with a 1:1 dilution of Sypro Ruby stain (Invitrogen) in nanopure water at room temperature in the dark. The gels were then washed for 30 min in a solution containing 10% methanol and 7% acetic acid. Gels were scanned on the Typhoon Variable Mode Imager (GE Healthcare) at 100 dpi and visualized with the 532 nm laser using the 610BP30 filter. The bands were excised from the gel using a bench top UV transilluminator at a wavelength of 302 nm.