Re: [ccp4bb]: protein oil out

[Edward Berry <eaberry@lbl.gov>]

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May depend on the concentration. Bile salt and polyoxyethylene
detergents can be salted out by high salt, giving phase separation.
Scarborough ((1994) Large Single Crystals of the Neurospora crassa 
Plasma Membrane H+-ATPase: an Approach to the Crystallization of 
Integral Membrane Proteins. Acta Cryst. D50: 643-649.) got the idea 
that a way to crystallize membrane proteins was to adjust conditions 
so that the detergent and the protein were salting out at the same 
time.

But if the protein by itself salts out as a liquid droplet, I can 
imagine a low concentration of detergent could help keep it in 
solution long enough to crystallize. 

Perhaps this kind of question will be covered in Hermann 
Schägger's forthcoming book: 
Membrane Protein Purification and Crystallization: A practical 
guide, Eds. Hunte, C., Schägger, H. and von Jagow, G., Academic
Press, in press

Thanks for no one jumping on my spelling error. I really do know
the difference between presence and presents.

Ed

"David J. Schuller" wrote:
> 
> On Tue, 27 Nov 2001, Edward Berry wrote:
> 
> > > 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?
> 
> isn't it the other way around?
> detergents and other surfactants help the oil and the water to mix.
> when the oil drops appear, try adding 0.1 - 5% of the usual suspects:
> MPD, 1,6-hexanediol, SDS, N-octyl glucoside.
> 
> =======================================================================
> "No philosophy book would be complete without mentioning doppelgangers."
>                                                - Daniel C. Dennett
> =======================================================================
>                         David J. Schuller
>                         modern man in a post-modern world
>                         MacCHESS, Cornell University
>                         djs63@cornell.edu