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From: B. Harris)
Subject: Re: could you possibly understand less?
Date: 3 Oct 1998 19:30:32 GMT

In <> writes:

>FWIW, it's my understanding that the "common" element in many
>nerve agent is phosphorous... i.e., many organophosphorous
>compounds affect the nervous system. They also make great
>insecticides. The fact that this particular agent contains
>fluorine most likely doesn't make it any more or less toxic.

  Well, as nearly as I can figure, what the fluorine in
organophosphorus-fluoride nerve gases does, is set up a good "leaving
group" (F-) so that nucleophilic attack on the phosphorus ends up
permanently attaching the organophosphate compound to the enzyme
(acetylcholinesterase).  That's the end of the enzyme.  Many other
organophosphate compounds are reversible inhibitors, and therefore are
not as toxic (on a milligram basis--- though all of them can kill, and
all do so in the same way).  Many insecticides acheive differential
toxicity to insects by attaching a sulfur atom to the phosphate, which
requires a good P450 hepatic oxidase to metabolize back to the active
phosphate.  Since herbivorous insects have much better P450 systems
than humans do, they get poisoned by this metabolic route.

   Note that none of this has anything to do with the toxicity of
fluoride (F-).  The fluoride evolved when the nerve gas reacts with the
enzyme has nothing to do with the toxicity of the enzyme.  If it
disappeared into the ether, the toxic effect would be the same.

                                       Steve Harris, M.D.

From: B. Harris)
Subject: Re: You want TOXIC? Re: Plutonium really the "most toxic poison known 
	to man"?
Date: Mon, 20 Oct 1997

In <62e8ll$oi5$> writes:
>"J. D. McDonald" <> wrote:
>>Gregg Eshelman wrote:
>>> Go breathe some fluorine gas.
>>Having done that many, many times, I can assure you that the smell
>>is enough to warn you long before immediately dangerous
>>concentrations are reached. It's exceeding smelly, somewhat like
>>ozone. The main fear of fluorine is not breathing it,
>>it's the fear that the gas regulator will catch fire. Having
>>had this happen to me once, and seeing it happen to somebody
>>else once, I assure you that it is the most fearsome thing
>>I have ever seen. It's truly amazing to see a piece of
>>stainless steel burning.
>>As someone else mentioned, phosgene is far more dangerous
>>to your health, as it has little if any smell.

 Phosgene has a lovely new-cut hay / chlorophil smell.  It's true that
it does not have a choking/warning kind of smell, like many poison

                            Steve Harris

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