[ccp4bb]: ccp4bb]: protein oil out

[Jeroen Mesters <jmesters@imb-jena.de>]

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Hello,

especially around the isoelectric point of a protein,
repulsive Coulomb forces decrease and attraction increases among
the molecules. The latter can lead to phase separation, as you
observed, resulting in one phase with low protein concentration
and the other with very high protein concentration e.g. oil.
The oil can be considered as a van der Waals gas.

Now this is actually not so good. The only thing you can do (besides
trying variants of the protein) is to try and crystallize it far away
from the isoelectric point. The latter will not be easy at all if not
impossible.

My advice, try combinations of PEG and salts at pH values far away from
the isoelectric point.

Jeroen.
-- 
Jeroen Raymundus Mesters, Ph.D.                           Alias Geronimo
Dept. of Structural Biology and Crystallography,  Institute of Molecular
Biotechnology, P.O.Box 100 813, D-07708 Jena, Germany.
Tel: +49-3641-656063, Fax: +49-3641-656062, E-mail: jmesters@imb-jena.de
http://www.imb-jena.de/www_sbx/home.html
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