EGTA

J. Martinez-Irujo jjmirujo at unav.es
Fri Oct 8 10:51:51 EST 1999


Peter wrote:

> In article <37FCCEF5.9E9DFB90 at unav.es>, jjmirujo at unav.es (" J.
> Martinez-Irujo") wrote:
>
> > In fact, both are metal chelons and have similar affinity for Ca2+,
> but
> > EGTA has 100 000-fold more affinity for Ca+2 than for Mg+2 (it is
> indeed
> > possible to remove calcium  leaving magnesium free in solution).
> > Dissociation constants  (expressed as pK=-logK) for Ca+2, Mg+2, Ni+2
> and
> > Cu+2  are (respectively)
> >
> > EDTA: 10.7; 8.7; 18.6; 18,8
> > EGTA: 10,9; 5,4; 13,6; 17,8
>
> What about Zn+2?
>
> For some reason, I seem to recall that EDTA is also capable of
> chelating Zn+2.
>
> regards,
> Peter Pediaditaki

Both  molecules strongly chelate Zn2+, EDTA (pK=16.5) and EGTA
(pK=14.5),  as well as several other cations (Cd+2, Fe2+, Fe+3, Mn+2,
Hg+2...). The selectivity toward these cations can be exploited, for
example, removing  traces of Ni+2, Co+2 or Zn+2 from soluble His-tagged
proteins, leaving Mg+2 free in solution.

No experience, however, on their effect on lysis buffers.

--
Juan J. Martinez Irujo

Departamento de Bioquimica
Universidad de Navarra
Spain





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