RE: nuclc acid fix (TCA+); also Barbi

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From:"Kellar, Eric" <kellarec@MSX.UPMC.EDU>
To:Histonet <>, "'J. A. Kiernan'" <>

Would that clever chemist happen to have been Johann Friedrich Wilhelm Adolf
von Baeyer?

> ----------
> From: 	J. A. Kiernan[]
> Sent: 	Tuesday, May 16, 2000 1:35 AM
> To: 	Histonet
> Subject: 	Re: nuclc acid fix (TCA+); also Barbi
> A lot of questions --->  A long answer. 
> Delete now if you aren't interested.
> On Mon, 15 May 2000, Mike King wrote:
> > > non-formaldehyde fixatives for better preservation of DNA and RNA
> > and John Kiernan replied:
> > ...In traditional histochemistry the best fixatives for DNA and RNA...
> >  Are you ... aware of any attempts to incorporate into fixatives
> reagents
> > such as trichloracetic acid, used to precipitate DNA in biochemical
> > preparations?  Or RNAse inhibitors?
> Reply:
>   RNase inhibitors: Diethylpyrocarbonate has been used, but (I think)
>   for the wrong reasons. I'll check and report if anything turns up.
>   Trichloroacetic acid (TCA) is a coagulant fixative of proteins.
>   According to M. Gabe's big book "Histological Techniques" (1975)
>   it preserves much more delicate structure than one would expect
>   when used alone. In real practice TCA is used only as a component 
>   of Heidenhain's SUSA. This is one of the best fixatives for light 
>   microscopy, but is currently _fixator_non_grata_ on account of
>   its containing mercuric chloride and other poisonous chemicals,
>   including TCA. The TCA in SUSA may help in precipitating DNA, but
>   the mixture also contains enough acetic acid to do this quite
>   adequately. Much higher concentrations of TCA _extract_ nucleic
>   acids from fixed tissues. TCA and also perchloric acid are still 
>   used histochemically for this purpose, as are DNase and RNase.
>   Please be aware that it's not "Susa's fixative." A Susa did not 
>   invent it, and neither did Heidenhain name this excellent fixative 
>   after his favourite bird. SUSA is an acronym for Sublimat-Saure 
>   (with a few umlauts that can't be sent by email), which roughly 
>   translates to mercuric chloride with acids.  Barbituric acid,
>   barbiturates and all the other "barbi-" compounds commemorate
>   "a lady named Barbara" revered and perpetuated by a particularly
>   perspicacious chemist of the 1890s who recognized an unconventional 
>   "acid" structure.  Can anyone remember the clever chemist's name? 
>   Eponyms are fun.
>  John A. Kiernan,
>  Department of Anatomy & Cell Biology,
>  The University of Western Ontario,
>  LONDON,  Canada  N6A 5C1

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