Dear Jacob,
this depends on type of metal ion, solvent accessibility of metal site
and pH.
E.g. the log of dissociation constants for histidine- Cu2+ / Ni2+/Zn2+
complexes are ca. 10.6, 8.7 and 6.6. Imidazol might pull out easily
these metals. Mg2+ and Ca2+ prefer coordination by oxygen. These should
be not affected, even at such high concentrations of imidazol. Also many
FeS proteins are successfully purified via IMAC without loss of Fe.
HTH
Guenter
Jacob Keller wrote:
Dear Crystallographers,
Does anybody happen to know whether imidazole is able to chelate metal
ions in solution? It seems reasonable that since it can compete for
binding to IMAC resins, it should have some affinity for at least Ni++
and Co++, but what about metal ions like Ca++ and Mg++? I assume that
the affinity is weak, but at the concentrations at which we are wont
to use it in our elutions (~100-500 mM), does it not seem likely that
other metal ions are being competed away from our proteins as well?
Jacob Keller
*******************************************
Jacob Pearson Keller
Northwestern University
Medical Scientist Training Program
Dallos Laboratory
F. Searle 1-240
2240 Campus Drive
Evanston IL 60208
lab: 847.491.2438
cel: 773.608.9185
email: [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
*******************************************
--
***********************************
Priv.Doz.Dr. Guenter Fritz
Fachbereich Biologie
Sektion Naturwissenschaften
Universitaet Konstanz
http://www.biologie.uni-konstanz.de/fritz
Universitaetsstrasse 10
Postfach M665
D-78457 Konstanz
e-mail: [EMAIL PROTECTED]
Tel. Office: +49-(0)7531 88 3205
Tel. Lab : +49-(0)7531 88 3687
Fax: +49-(0)7531 88 2966
