Re: [ccp4bb]: protein oil out

[Edward Berry <eaberry@lbl.gov>]

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hongmin LI wrote:
> 
> hello,
> 
> Sorry this question is not CCP4 related. I am working on a protein which is highly soluble. I can easily concentrate it to
> 60mg/ml. While the protein was not precipitated from most chemicals (PEG, (NH4)SO4, molonic acid, .....), instead, it is oil out.
> Does anybody have similar problem before? Any suggestions ? Thanks in advance.
> 
Do you mean that these precipitants induce phase separation, 
with droplets of protein-rich solution separating out from 
the bulk phase? I don't know if this happens with pure proteins,
but in the presents of detergents or other additives there
can be phase separation, with hydrophobic proteins partitioning 
into the additive-rich phase. Do you have detergents or
hydrophobic/amphiphillic additives present?

There is some report of these "coacervate droplets"(?) 
serving as nucleation centers for crystals growing out
into the aqueous phase, so you might want to save a tray 
and check periodically even if it looks hopeless now.

Ed