Dilute both the Protein and DNA before mixing them at the molar ratio
you require - I would aim to have the protein component at around 1 mg/ml.
Mix, then concentrate together, till you reach the concentration you want.
Antony.
On Wed, Oct 1, 2008 at 6:52 PM, E rajakumar <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> wrote:
Dear All
Sorry for non-crystallography query. I am working on
DNA binding protein, while mixing DNA with protein for
preparing Protein-DNA complex for crystallization,
protein is precipitating. pI of the protein is 9.3
and in 15 mM HEPES 7.0, 150mM NaCl and 5% glycerol.
Concentration of the protein used for mixing with DNA
is 8 mg/mL. DNA to protein molar ratio is 1.2. Please
advise me how to prevent precipitation. Is changing of
buffer pH and adding divalent cation like MgCl2 can
help in preventing precipitation?
Thanking You
Rajakumara
E. Rajakumara
Postdoctoral Fellow
Strcutural Biology Program
Memorial Sloan-Kettering Cancer Center
New York-10021
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