Re: Zinc in fixation

From:"J. A. Kiernan" (by way of histonet)

On Tue, 24 Jul 2001, Connolly, Brett M wrote:

> Can someone please explain the function of zinc in tissue fixatives?

The zinc ions coagulate protein - much the same action as
an astringent lotion containing zinc sulphate. The best
fixatives for light microscopy of paraffin sections are
mixtures that contain a coagulant and a cross-linking
agent. The latter is pretty well always formaldehyde.
The former can be picric acid, mercuric chloride (the
best but toxic), alcohol, a zinc salt etc etc. Acetic
acid does not coagulate proteins but it does precipitate
DNA, thereby providing characteristic patterns of
chromatin in interphase nuclei.
John A. Kiernan
Department of Anatomy & Cell Biology
The University of Western Ontario
London,  Canada   N6A 5C1

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