Peter pxpst2 at
Mon Mar 23 11:14:32 EST 1998

In article <wendy-2303981521450001 at>,
wendy at (Wendy-Anne Smith) wrote:

> Hi,
> I can't seem to find any information which tells me how the mechanisms of
> action of EDTA and EGTA differ.  I would be greatful for any information
> that could be passed on.  In addition to this in what instances would EGTA
> be used either alone or in combination with EDTA?
> Thanks
> Wendy
> -- 
> Dr. Wendy-Anne Smith

EDTA  and EGTA are chealating agents or poldendate ligands.
EDTA is generally considered to be broad in the range of metal ions that
it can coordinate with.  The common feature of most chealating agents is
the nitrogen/oxygen lone pairs that forms the bonds with the metals.  The
Nitrogen/oxygen has a lone pair that can be donated to a Metal to form a
bond.  Since EDTA(anion form) has two N: and four carboxylate groups, it
can form six bonds with metals(hexadendate complexing agent).  When fully
coordinated with a metal the carboxylate ion groups are arraged
octahedrally around the Metal core.

Genarlly speaking this is how most chealating agents work though some are
more specific for certain metals.  EGTA is most specific for Ca.
For more info find a good Inorganic text.
Peter Pediaditakis

"Don't you eat that yellow snow
            watch out where the Huskies go"    FZ


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