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Re: [Phys-l] Isotope chemistry and physics



On 16-Mar-09, at 6:42 PM, Bill Nettles wrote:
The diffusion and mitosis effects would be the strongest, but poisonous...well in the right quantities, NaCl is poisonous, K is poisonous...heck, we've all got K-40 in us, and that stuff is radioactive!


I asked the question regarding D2O toxicity some time ago (maybe on the CHEMED-L list). I am grateful to John Cooper for hanging on to the following, as PHYS-L archives don't go back to 1995!

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From phelming@JAGUAR1.USOUTHAL.EDU Wed May 17 18:05:29 1995
Date: Wed, 17 May 1995 11:25:50 -0500
From: "Paul A. Helminger" <phelming@JAGUAR1.USOUTHAL.EDU>
Reply to: Forum for Physics Teachers <PHYS-L%UWF.BITNET@uga.cc.uga.edu>
To: Multiple recipients of list PHYS-L <PHYS-L %UWF.BITNET@uga.cc.uga.edu>
Subject: Re: Heavy water and sweat

About D2O consumption and sweating:

Upon reading the discussions on D2O and sweat on PHYS-L it was my
vague recollection that D2O consumption is harmful to body functions. I
posed the question of the effects of D2O consumption to a chemist friend
here on campus. His response is included below.

Paul Helminger
Physics, Univ of South Alabama
phelming@jaguar1.usouthal.edu

-------------------------------------------------------------------------

Paul,

If you drank pure deuterium oxide over a long period of time, you would
not sweat at all because you would be dead.

The following information refers to mammals.

1. Heavy water (D2O) is absorbed by the gastrointestinal system and quickly
equilibrates with other body fluids. It is NOT selectively excreted by
the kidneys, so a large buildup of D2O is possible. The D2O then slowly
enters all cells and equilibrates with intracellular water.

2. With mouse and rat studies involving 50% D2O, death occurs in 4-5
weeks. With 75% D2O, death occurs in less than two weeks.

3. In mammallian studies, there have been reports of impairment of renal
function, disturbances of the central nervous system, hormonal imbalance,
and anemia. One other possibility is death due to water deprivation,
because deuterated mammals seem to drink less water and thus eat less food,
confirmed by 1) loss of body weight up to 33%, 2) aggression and ferocious
activity (similar to control studies of dehydrated mammals), and 3) blood
levels consistent with severe food deprivation.

4. Why does this happen? Probably due to the effect of deuterium on the
rate of enzymatic reactions. This process is called the "solvent isotope
effect". Also, sometimes the enzyme picks up a proton from the solvent.
Picking up a deuterium instead leads to a "primary isotope effect". In
both of these cases the effect of deuterium is to slow down the enzymatic
reaction. In the "primary isotope effect" case, the zero point energy of
D is significantly less than H, leading to a large drop in the energy of
the reactant. The transition state is less affected, so that the
activation energy increases for the deuterium isotope. In the "solvent
isotope effect" case, the increased viscosity of the fluid leads to a
slower rate of reaction, since it takes longer for the solute molecules
to meet and react. Obviously, these effects are not so clear cut,
because the relationship between solvent and reactant is complex.

5. Conclusion: D2O is fatal because it slows down enzymatic reactions in
the body, leading to fatal symptoms. However, this would only occur if
large amounts of D2O were injested over a long period of time. Drinking
a glass of D2O is not fatal, and there is no LD50 (lethal to 50% of the
population) reported in the Merck Index or in Toxicology Tables.

Source: Biological Effects of Deuterium, J.F. Thomson, Macmillan, 1963.

Sid
Young Department of Chemistry
University of South Alabama
Mobile, AL. 36688
syoung@jaguar1.usouthal.edu


From HILLEKER@CITADEL.EDUThu Apr 25 18:39:17 1996
Date: Thu, 25 Apr 1996 17:17:32 -0400 (EDT)
From: "Russ Hilleke, Physics Dept (3-6953)" <HILLEKER@CITADEL.EDU>
Reply to: phys-l@atlantis.cc.uwf.edu
To: phys-l@atlantis.cc.uwf.edu
Subject: Re:drinking D2O

Barlow Newbolt asked " Years ago I read that an animal with only heavy
water to drink would die of thirst. . . . Is this statement true?"

About 15 years ago, I heard a presentation about a research program
at Argonne National Lab concerning the effects of deuterium on
living systems. I have not been able to find my notes from the talk,
so the following is my recollection.
The purpose of the work was to study metabolism in large mammals
(they used Beagles in the study) by substituting deuterium for hydrogen
in the animals' makeup. The animals drank heavy water and the fraction
of deuterium replacing hydrogen in the animals' tissue was measured.
They observed how this affected the rates of various biochemical
processes in the animals. As I recall, deuteration fractions in the range
30-50% killed the animals.
As to why this happens, I found reference to a paper (Kihara & McCray,
Biochim. biophys. Acta 292, 297-309 (1973).) in which the
authors found that reconstituting freeze-dried bacteria and mitochondria
with D2O instead of H2O increased oxidation/reduction times of cytochrome b & c
by a factor of sqrt(2) (see Quantum Mechanical Tunneling
in Biological Systems by Don DeVault, pa 46). So the animals don't die
of thirst, but their metabolism rates are sufficiently perturbed that
they don't survive.

Russ Hilleke
Physics Dept
The Citadel

*******


---
Michael Porter
Colonel By Secondary School
Ottawa, Ontario, Canada