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Concentrating protein of a particular size - (Mar/13/2012 )

Besides using commercially available filtered tubes, has anyone tried concentrating total protein? Would this technique concentrate proteins of all sizes or would the smaller proteins be lost during the process?

-science noob-

depends on the molecular weight cutoff of the membrane.

you can concentrate total (or near total) proteins in other ways, which way depends on whether you are willing to denature your protein.

non-denaturing, you can saturate your protein solution with ammonium sulfate and pellet the protein. then resuspend in a smaller volume with an appropriate buffer (dialyze away residual ammonium sulfate).

you can do another precipitation with cold acetone.

you can precipitate with polyethylene glycol.

denaturing, you can precipitate with trichloroacetic acid (tca) or acetone/tca.