Mini centrifuge filters for protein binding studies

[Hugh Goldie]

I would like to use mini centrifuge filters for studies of small radioactive 
ligands binding to a purified protein.  At present I have a pressure cell,
with eight chambers, which uses nitrogen gas pressure to force samples 
through 10,000 MW (Amicon TM10) filters; however, this is rather cumbersome 
and slow.

Commercial filter units are available with 10,000 MW cut-offs; however, these
are intended for _concentrating_ small protein samples.  They are constructed
so that the solution being filtered will not all pass through the filter.  
(They have a "retentate volume" of 10 microlitres.)  

What I need are minicentrifuge tubes with zero retentate volume (i.e. all
the solution passes through the filter and the protein is left behind with
bound radioactive ligand.)  The total volume of my binding reactions is 100 
microlitres, so a 1.5 mL centrifuge tube would be a good size.  Does anyone 
know where to obtain these?  I am trying to make some from various 1.5 mL
and 0.5 mL tubes, but it is tricky.

--Hugh

--
Hughes Goldie, Department of Microbiology and Immunology
Saskatoon, Saskatchewan, Canada
goldie at duke.usask.ca