Can you see a viral pellet?
The virus pellet cannot actually be seen. The pellet that one does see in the bottom of the tube is derived from serum proteins present in the media of the transfected culture. To separate the virus from the protein pellet, simply leave the DMEM (200�l) on the pellet for 5-10 minutes at room temperature, then gently pipette this suspension up and down about 30 times being careful not to generate air bubbles. Then transfer the virus-protein suspension into a sterile microfuge tube or cryovial and microfuge for 4 minutes at high speed. This centrifugation step will pellet the protein in the bottom of the tube (it sticks rather tight to the wall of the tube). Then transfer the supernatant, which contains the virus particles, into another vial. From there, aliquot the virus in smaller volumes. It doesn't really matter how much you resuspend the virus in after centrifugation. It depends on how concentrated you need the virus. We do not recommend resuspending in less than 100�l.