PEG is usally fairly poly-disperse unless you pay extra for a well
defined lot. The molecular weight given is usually the mean size.
If you are not concerned with recovering the protein in its native
conformation (eg for gel or maldi analysis) I'd suggest precipitating
with trichloroacetic acid. This works fairly well although some
detergents also precipitate. I wash twice with ice cold acetone to
insure removal of residual TCA. If resuspension is dificult try ading
some concentrated buffer (eg 1/10 vol 1M Tris)
mark bowen
