PERCOLL density gradient - how to make the percoll density gradient in one 15-ml tube? (Mar/07/2005 )

hello, everyone, i am working on cell heterogeneity , especially on cell growth difference in the tumor cell line. i would like to isloate subpopulation by the percoll density gradient. but i failed in setting up the percoll density gradient in the 15-ml centrifuge tube. to be exactly, i just pipetted 2ml each density percoll with 1-ml pipette and add it onto the tube wall carefully but i am afraid the interface was disturbed and what i got was an even solution but not a density gradient. would anyone tell me how to do it? what tools should i use? thanks a lot.

I believe that centrifugation will set the gradient right

Simon