Re: Glutaraldehyde: a different kind of cautionary tale

Katharine Thayer wrote:
>
> MARTINM wrote:
>
> >
> > That's very interesting. This seems to confirm what is stated in a paper
> > dealing with dichromated gelatin: there is a fundamental difference between
> > chrome hardening and aldehyde hardening. "When the commonest organic
> > hardener (formaldehyde) is used, the gelatin molecules bind to their amino
> > groups at relatively high pH values and the carboxylic groups are considered
> > absolutely free."(Mazakova et al, Dichromated gelatin for volume holographic
> > recording with high sensitivity. Part II, Optical and Quantum Electronic 14,
> > 1982, p.318)
> > "The results from the experiments show that if for bias hardening of
> > dichromated layers a hardening agent is used which binds not the carboxylic
> > but, say, the amino groups of the gelatin molecules, the light energy is
> > used more thoroughly, i.e. the sensitivity improves." ( p.319)
> > I ignore how this relates to gum crosslinking though.
>
> This is interesting, thanks. How it relates to gum crosslinking is
> anyone's guess, since there is little or no information extant on gum
> crosslinking per se and what is thought about it is mostly extrapolated
> from other processes. But I think it's unlikely that amine groups are
> involved. Amino acids form only about 1% of the total gum (N is then a
> fraction of 1%) and furthermore, most of that is locked so deep in the
> molecule (which is thought to be somewhat spherical in shape) that it
> can't be attacked by proteolytic enzymes; it seems reasonable (to me
> anyway) to assume that entities that are unavailable to be attacked by
> enymes are also unavailable for crosslinking.
>

I guess I didn't entirely complete my thought here. I meant to say that
while it's quite unlikely IMO that amine groups are involved in gum
crosslinking, it's also somewhat unlikely that carboxyl groups are
highly involved either, since only one of the four sugars that make up
the gum (glucuronic acid) contains a carboxyl group, and it's not one
of the more prevalent sugars (18% of total sugar content) in the gum.
kt
Received on Thu Apr 29 19:51:18 2004