I am trying to purify zika virus from cultured vero cells. And I have 10ml-size ultracentrifuge tube (Hitachi, cat# S303922A)

I heard that the longer the centrifuge separates, the lower the band is formed. And someone told me that I can get clear band if I centrifuge for longer time. Am I correct?

I am learning the protocols from internet and papers. But, they experiment on different conditions.

- at 116,000xg for 1hr

- at 28000rpm for 4hr

- at 160,000xg for 8hr

- at 120,000xg for 18hr

These are some of the conditions that I have read

So, My question is "how long should I run the ultracentrifugation in order to get virus band?" "What if I run too long time? Will virus be formed lower part or precipitated? Will it remain in its position(density buoyancy)?"

Please let me know the relationship between centrifugation time and band position.