On Wed, 2012-11-07 at 11:29 -0600, SD Y wrote:
> https://www.dropbox.com/s/4jd6gdor87ab9lj/Zn-coordination.png
Your sigma level of 6.5 seems a bit low, so maybe it is a different
metal. But on your main question - yes, metal binding proteins do pick
up metals from the media. Once metal is coordinated, it is not very
likely to leave, unless you remove it on purpose.
Place Zn there and refine. Then see if you have a) residual density and
b) B-factor mismatch with coordinating residues. If so, you may try
different metals and see what fits better, although at this resolution
it's tricky. It is also possible that you have partial metal occupancy.
Depending on the wavelength you used you may be able partially confirm
or completely reject zinc option by looking at anomalous difference
maps. If you have more crystals and access to tunable beam, you should
be able to run fluorescence scan to see what metal you got. If not,
there is ICP-MS for metal identification, you would have to run it with
your protein sample and you need access to an instrument.
Cheers,
Ed.
--
I don't know why the sacrifice thing didn't work.
Science behind it seemed so solid.
Julian, King of Lemurs
