Re: glutaraldehyde

From: "T. E. Andersen" <postlister@microscopica.com>
Subject: Re: glutaraldehyde
Date: Thu, 18 Mar 2004 00:43:17 +0100

> You may again be right, of course, but I don't see how gelatin can be
> *that* different from other proteins? I have not read the literature
> from the photo industry on this, but I *have* read quite a few volumes
> and articles from tissue research. Are you suggesting that the basic
> mechanisms of fixation are somehow different in gelatin? If so, why is
> that the case?

The besic chemical mechanism of hardening, that is, crosslinking at
free amino groups, is the same, but resulting change in mechanical
properties, etc. are not necessarily the same. Also, there are
differences in the procedures and materials used. One difference is
that tissue fixation is done to mostly solid protein, and the amount
and concentration of aldehyde fixative used is considerably higher
than the amount of glutaraldehyde needed to harden aquaous phase of
gelatin. (I am familiar with transcardiac and immersion perfusion of
tissue, because that's a part of what I do during day.)

> > Glutaraldehyde is superior cross linking agent to glyoxal and
> > formaldehyde because GTA is bifunctional, meaning that it can attach
> > to two separate gelatin molecules. I suggest you study literature
> > before making speculative comments here, again.
>
> Why do you consider the glyoxal monofunctional? It, too has two aldehyde
> groups. Does only one react with proteins?

Here are additional papers on glutaraldehyde. The first one is
concerned about the structure in aquaous solution. The second one is
probably most relevant to your question of chemical mechanism
underlying hardening of collagen as well as gelatin.

Whipple, E. B. and Ruta, M. 1974. Structure of aqueous glutaraldehyde,
J. Org. Chem., 39, 1666-8.

Khor, E. 1997. Methods for the treatment of collagenous tissues for
bioprotheses. Biomaterials, 18, 95-105.

Jayakrishnan A. and Jameela, S. R. 1996. Glutaraldehyde as a fixative
in bioprostheses and drug delivery matrices. Biomaterials, 17,
471--484.

> Ps. I saw the ref. list you sent in another posting. That paper dealing
> with the effect of aldehydes on bread and croissants really makes me
> want to bake my own bread.... Why on earth would anyone want to use
> aldehydes on bread????

Aldehyde agents are used on hard gel capsules as well.

--
Ryuji Suzuki
"All the truth in the world adds up to one big lie." (Bob Dylan 2000)