Ho,
interesting case.
Glycerol actually forms weak complexes with metal ions:
Journal of Inorganic Biochemistry,60 299-302 (1995) and some references
therein.
But to be true, I am surprised that glycerol at concentrations of 10-15%
(?) as used in cryo conditions can compete with a metal ion binding
site in a protein. I remember I myself did titrations with Zn2+ in the
presence/absence of 5% glycerol and did not observe any effect on the
binding. There might be another effect (?) although I have no idea what
it might be.
I am working with a metalloprotein that binds cobalt and iron. I
was surprised that the solved structures showed the crystals
cryoprotected with glycerol are metal free while crystals
cryoprotected with ethylene glycol had the metals present. Both
cryoprotectant solutions contained metal in the 10 mM range and are
buffered at pH 9. I assume glycerol must be a weak chelator otherwise
it wouldn't be so ubiquitous in protein biochemistry. Has anyone else
experienced this before with glycerol?
Ho
UC Berkeley
--
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