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Re: [ccp4bb]: divalent ion selectivity
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Dear Minghui,
>From a CHEMICAL point of view the three species Mg2+, Mn2+, and Zn2+ are,
indeed, very different.
Mg2+ has a significantly smaller radius than Mn2+ and Zn2+, which can have
some influences on the structure.
Mg2+ and Zn2+ are NOT redox active, while Mn is known in the oxidation states
-3, -2, -1, 0, 1, 2, 3, 4, 5, 6, and 7 (even though the Mn2+ species is
relatively stable in aqueus systems).
Mn2+ makes komplexes as a d5 high spin cation, which allows a large variety of
coordination-geometries, while Zn2+ (d10 configuration) is only known in
tetrahedral (4 ligands) and octahedral (six ligands) coordinations. Compare
that e.g. with Cu2+, a d9 cation, which makes planar komplexes instead of
tetrahedral ones for 4 ligands and the octahedral coordination is
significantly distorted due to a Jahn Teller effect.
The coordination geometry of Mg2+ is mostly octahedral with 6 ligands, but
some cases with tetrahedral coordination sphere (4 ligands) are known as well.
I am not sure whether this answers your question (probably not), but that's
all I can contribute.
Best wishes
Peter
Li Minghui <lmh@moon.ibp.ac.cn> said:
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>
> Dear all,
>
> Can any one tell me from the structural point of view
> why some kinases have higher activity with Mg2+ ions, while
> some others prefer Zn2+ or Mn2+.
> And what is the meaning for this kind of divalent ion selectivity?
>
> Thank you very much.
>
> Minghui Li
>
> National Laboratory of Biomacromolecules
> Institute of Biophysics, Academia Sinica
> Tel: 86-10-64888507
> E-mail: lmh@moon.ibp.ac.cn
>
--
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Dr. Peter Mueller fon: +1-310-825-1420
UCLA-DOE Laboratory of Structural Biology fax: +1-310-206-3914
and Molecular Medicine
201 MBI
BOX 95157 http://shelx.uni-ac.gwdg.de/~peterm
Los Angeles CA 90095-1570 peterm@mbi.ucla.edu
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