Sorry for the non-ccp4 post.

I have purified an 18kDa membrane protein and want to concentrate the protein from gel filtration fractions, which are in buffer containing 0.05% DDM (well above the CMC for DDM). My colleague was able to concentrate a 30kDa membrane protein using a 100kDa MWCO concentrator but I am not sure if I can do the same without losing protein in the flowthrough. On the other hand, if use too low a MWCO for the concentrator, then I'm concerned that I may end up concentrating the DDM and end up with too much detergent in the final sample. 

Any tips about how to concentrate my low MW protein without concentrating the DDM? 

Many thanks.

Raji

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Raji Edayathumangalam
Instructor in Neurology, Harvard Medical School
Research Associate, Brigham and Women's Hospital
Visiting Research Scholar, Brandeis University