help: virus purification problem

[Min-Ho Lee]

Hello!
I have a problem in purification of an insect virus. 
When viral particles were collected (as a white band) in sucrose 
gradients (30%/60%), I transferred the band to a new ultracentrifuge
tube.
Then, I spun the tube at 100,000g for 1 hr. But, I have no get any 
pellet. I thought that viruses have no spun down because of 
sucrose buoyancy. 
So, I allowed the solution at 4oC, overnight, stirred it roughly and
ultracentrifuge at 100,000g for 1 hr. But, I have no any pellet, too!

Is there anyone know about it?
Why virus particles were spun down?
What can I do for purification of the virus particles?

Your Sincerely, Min-Ho Lee
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mhlee at bric.postech.ac.kr
Web for the Korean Entomologist (my home page):
http://bric.postech.ac.kr/about/mhlee/
BRIC (Biological Research Information Center), POSTECH
http://bric.postech.ac.kr
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