Sodium Sulfate Precipitation Problem

[Josh Levin]

On Mar 3, 4:04 am, WS <novalidaddr... from nurfuerspam.de> wrote:
> Dear Colleagues,
>
> I am about to precipitate some purified IgG by dialysis against 18% m/
> v sodium sulfate (as I want to label the protein with an amino
> reactive reagent, I cannot use ammonium sulfate, it's a convenient
> quencher). I get a huge amount of precipitate after incubating at room
> temp over night. However, the precipitate is floating on top of the
> solution, especially after centrifugation (2000g for 20 min at 25
> degC).
> Any idea how I could obtain an ordinary pellet where one would expect
> it?
>
> Many thanks and best regards,
>
> Wolfgang

Hi Wolfgang-- is it necessary to precipitate the IgG?  You might try
concentrating it in a Centricon or some other miniconcentrator.  In my
experience the IgG will denature after precipitating.  Typically
concentration prior to amino conjugation works pretty well.

Josh Levin
ResearchDesignExperts