J. Martinez-Irujo jjmirujo at
Thu Oct 7 12:07:41 EST 1999

Peter wrote:

> In article <7ti5qu$7cg$2 at>, "Chong Wai Yin( Zhang
> Weixian)" <wychong at> wrote:
> > Hi people! Can anyone tell me are there any difference between using
> > and EGTA in lysis buffer. Is the function of EGTA the same as EDTA?
> Thank
> > you for answering.
> EDTA- chelates only Ca+2
> EGTA- Chelates all divalent cations
> In a lysis buffer, I use both as an insurance policy.
> Peter

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

Hope this helps.

Juan J Martínez Irujo
Departamento de Bioquimica
Universidad de Navarra

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