Concentrating Small Protein

[Michael S Curtis]

I am trying to concentrate a small protein (~6KD). I am currently using a 
Cetricon-3 (3000 MWCO), however I am getting alot of the protein going through 
the membrane. Does anyone know of a supplier who has a smaller MWCO 
centrifugation/ultrfiltration apparatus, the smallest Centricon I know of is 
the 3000 MWCO. Does anyone know of a better way to concentrate such a small 
protein? Any suggestions would be greatly appreciated.

Thanks in Advance.

Mike Curtis
curtis at bms.com