Disposal of Hoechst waste

David F. Spencer dspencer at is.dal.ca
Fri Feb 14 16:07:36 EST 1997


In article <Pine.SOL.3.95q.970212115159.19406A-100000 at suma3.reading.ac.uk>,
"J. G. Gibbings" <sbsgibin at reading.ac.uk> wrote:

> Hi,
>         Can anyone out there advise me on how to dispose of the possible
> mutagenic Hoechst dye waste solutions (0.1mg/L). We use the dye to
> quantitate DNA on the DyNA Quant 200 Hoefer flurometer. 
>         Thanks.
> 
>         George.

George:

If you are very conscientious you could bind the dye to activated charcoal and
have that incinerated, but if you're dealing with litre quantities of solution
that procedure would be pretty laborious.  Probably the one thing that everybody
would agree on is that you shouldn't treat the dye with hypochlorite bleach,
because although that will decolourize it, it will almost certainly convert the
dye into various genuinely undesirable chemicals.

I am not aware of any evidence that the Hoechst dyes (bisbenzimides) are in fact
mutagenic.  As was demonstrated by some nice work by Werner Mueller in the
mid 70's (he has three papers in Eur. J. Biochem. 54, 1975; for this specific
dye see Eur. J. Biochem. 54, 385-394 (1975) ) Hoechst/bisbenzimide is not an
intercalating dye as, for example, ethidium bromide or the acridines are.  In
fact he determined that apparently all dyes that have A-T binding preferences
(this would include DAPI, Berenil, methyl green and the bisbenzimides, although
he studied only the latter two of this group) bind to the outside of the DNA
helix. Intercalating dyes by contrast have slight to high preferences for G-C
rich regions in DNA and they obviously have the potential for generating frame
shift mutations if they are bound to replicating DNA; some members of this
group have photosensitizing or photodynamic activities which can in appropriate
circumstances cause DNA damage.

I would suggest that Hoechst dyes represent no greater threat (possibly less)
than say Coomassie Blue and any number of standard lab dyes that have never been
implicated in anything worse than possibly mild skin irritation. (The whole
issue of ethidium bromide disposal is of course frequently engulfed in an
irrational hysteria.)

The bisbenzimides were originally screened (if I recall correctly) as potential
trypanocide or maybe antimalarial drugs, so at worst the dye might present an
environmental threat to Trypanosoma or Plasmodium species;  neither group seems
to have many apologists.

Dave Spencer

-- 
David F. Spencer, PhD
Dept. of Biochemistry
Dalhousie University
Halifax, Nova Scotia, Canada

dspencer at is.dal.ca
dspencer at rsu.biochem.dal.ca



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