I only was looking for protocols to isolate particles in a range between 40-60nm, not specifically alphaviruses. Particles seem to be damaged after 16h of centrifugation.
Pacific Northwest Cryo-EM Center, Oregon Health and Sciences University, Portland, USA
Can you please give us more information on the type of virus you are trying to purify, the centrifugation speed and if you've followed the protocol exactly or if you've made any modifications to it?