Could it be a formate ion (HCO2−)? _Gang
-----Original Message-----
From: CCP4 bulletin board [mailto:[email protected]] On Behalf Of Stephen
Cusack
Sent: Monday, October 09, 2017 5:40 PM
To: [email protected]
Subject: [ccp4bb] help identifying unknown density
Dear All,
I am refining the crystal structure of an E. coli expressed protein at 2.65
A resolution. The crystals grew in
0.1 M MES pH6, 0.7 M sodium formate pH 6. Ni-NTA was used in the purification.
There are four molecules in the asymmetric unit. A particular histidine in each
molecular has clear, strong extra density which looks like a metal bonded to an
imidazole nitrogen (distance approx 2 A) with three other co-ordinating atoms
in a triangular planar arrangement (see attached screen shot for unbiased extra
density, atoms are only put in the density for illustrative purposes).
Has anyone seen anything like this ? Any suggestions ?
thanks very much
Stephen
--
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Dr. Stephen Cusack, FRS
Head of Grenoble Outstation of the European Molecular Biology Laboratory (EMBL)
Group leader in structural biology of protein-RNA complexes and viral proteins
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