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PEI and ammonium sulfate ppt

PEI and ammonium sulfate ppt - Protein Forum

PEI and ammonium sulfate ppt - Protein Forum

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Old 03-10-2008, 02:09 PM
Dr Engelbert Buxbaum
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Default PEI and ammonium sulfate ppt

Am 08.03.2008, 17:01 Uhr, schrieb Tsu-Fan Cheng <[Only registered users see links. ]>:

Almost any protein can be precipitated with AS, that is just a question of
concentration. Some proteins already precipitate at 20% satturation,
others only at 80%.

In this case you apparently have a protein that precipitates at relatively
low conc of AS, before the PEI precipitates. That's fine, just spin down
the protein, remove the supernatant with the PEI, wash the precipitate
with AS solution of the same conc as used for pelleting, spin again,
discard the supernatant and redissolve your protein in a buffer of your

Depending on what you want to do you may have to remove the remaining AS
by either dialysis or gel filtration (''desalting column'').

Note also:

- many proteins store very well as AS precipitate in mother liquor at 4
deg C.

- Add the AS slowly and in the cold. Stop the addition when just a slight
haze develops in the protein solution, than keep o/n in the fridge. That
way you get best separation between your protein and whatever remains in

- Any book on protein purification will discuss this in more detail.
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ammonium , pei , ppt , sulfate

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