[ccp4bb] Differentiating bound Mn & Ca.

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CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Re: Surface complementarity
From: Mike {- dot -} Lawrence {- at -} CSIRO {- dot -} AU Mike {- dot -} Lawrence {- at -} CSIRO {- dot -} AU
Date: 2007-04-15

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Subject: Re: Differentiating bound Mn & Ca.
From: Kay Diederichs kay {- dot -} diederichs {- at -} UNI-KONSTANZ {- dot -} DE
Date: 2007-04-16

Subject: Differentiating bound Mn & Ca.
From: David Briggs bassophile {- at -} GMAIL {- dot -} COM
Date: 2007-04-16

Dear all.

I have recently solved a structure in-house, 2.8A, CuKa.
I have a metal ion bound very obvious hepta-valent co-ordination, which
would suggest either Ca or Mn.
Neither was present in the crystallisation setup, but there was some Mg
around, which has contaminants of both Ca & Mn.
At 2.8A, I don't really think I can reliably discriminate between 2.15A &
2.36A distances to coordinating atoms (
http://tanna.bch.ed.ac.uk/newtargs_06.html).
The B factors for refined Ca are 18, and Mn 30. The B-factors of
coordinating atoms vary from... 18 > 30 - so no help there.

I have a nice clear 6sigma anomalous difference peak, but then, according
to http://skuld.bmsc.washington.edu/scatter/ both Ca (f" ~1.3) and Mn (f"
~2.8) scatter anomalously at that wavelength.

The obvious solution is go to a synchrotron and scan around the Mn edge and
see what happens, however, whilst waiting for beam time, is there any way I
could... oh I don't know, use the peak in my anomalous difference Fourier to
figure out what anomalous signal would be required to generate a peak of
that size - a sort of back-transform???

Is this do-able, and if so, how would one go about it?

Cheers,

Dave

--
---------------------------------------
David Briggs, PhD.
Father & Crystallographer
www.dbriggs.talktalk.net
iChat AIM ID: DBassophile
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CCP4bb navigation

CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Re: Surface complementarity
From: Mike {- dot -} Lawrence {- at -} CSIRO {- dot -} AU Mike {- dot -} Lawrence {- at -} CSIRO {- dot -} AU
Date: 2007-04-15

Next message:
Subject: Re: Differentiating bound Mn & Ca.
From: Kay Diederichs kay {- dot -} diederichs {- at -} UNI-KONSTANZ {- dot -} DE
Date: 2007-04-16