It really depends on your protein and how many other proteins will salt out at the same percentage as your protein of interest. 70% could be feasible, but you'd really have to determine it experimentally.

Dear Anton

why your plasmids did not contain a cleavable his tag? it may simplify a lot your purification work. is it related to the properties of your protein ?

however as Lindsey wrote the result of ammonium sulfate precipotation it really depends from the properties of your protein because 70% is not so high % but it depends at with % your protein precipitate.

what is the pI of your proteins?

which amount of each protein you wuold like to purify?

because i'm not a fun of protein precipitation and if pI of the variants are similar and you need a small amount of protein you can try also to perform a Simple ionic exchange (anionic or cationc to be chose on yj using a small approach adding the

basis of the pi) with out gradient in a Protocool similar to imac. For examples 100ul of resin added on a gravity coloumn and use a binding buffer with low salt to loda the protein and wash the unbounded proteins and one elution with hih salt to elute.

of course with out linear salt gradiemt you cannot reach high purity Level but if you chose the right ph for binding condition and you wash with many cv of binding buffer i think that 70% is feasible and you can handle many small coloumn in parallel (12-24)

ciao

Manuele

Dont have any information of your protein. All answers for your question are " may be". 70% purity might be possible - Only you can answer it by doing experiment.

Dear all,

thank you very much for your answers!

I tried ion exchangers before for this protein, and it was only binding to hi-trap columns but to prepared by myself (for unknown reasons). And in this case I would like to avoid the FPLC at all.

I guess I'll just have to do the experiment :-) The fact that by varying salt (NaCl, KCl etc) concentration one can change the % at which protein precipitates is giving me hope to separate it from the junk.

Best wishes

Anton