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Re: DNA DSB damage from 3 to 10 eV electrons
I missed this. I'd read the Perspective in Science so I'd passed by this note.
But the implication is the opposite of this premise: This paper kills the
false notion that ionizing radiation is a unique source of dsb's! Biology
fundamentally works on electron transfers, and this shows that (low-energy)
electrons can be captured on one DNA strand with a reaction that includes
breaking the other strand. (And dsb's are readily repaired [not to ssb
standards! :-)] with some detailed descriptions of the mechanics of the
process in the last few years; or the damaged cell is removed!)
But, cancer isn't a function of damaged DNA/cells. If your repair/control
processes are working, the vast number of damaged cells in your body (a
trivial fraction are from radiation] will NOT progress to a tumor. If/when
promoted, they'll be destroyed. But, sufficient rad doses overwhelm repair
processes (NOT from numbers of damage events, which are still trivial compared
to oxidative metabolism) that leave unrepaired latent damage, that progress
when immune and other control processes degrade (cancer is a strong function
of age!).
Natural radiation seems essential to those functions, when it's blocked,
biological systems fail. High natural doses, or rad supplements, stimulate
those functions when your immune/control functions are otherwise
over-stressed. See the positive results in, e.g., radium/radon spas etc., and
the molecular biology of dose-response to moderate doses that have been
identified here often. (That's why mice in SPF conditions w/ and w/o low-dose
supplements don't show significant effects. But animals in natural conditions,
and humans in less-than-ideal dietary, bacteriological, and other stress
conditions, DO show a significant difference!) See, e.g., the recent mice
study in France with longer lives for the groups with 7 and 14 rem/year, and
e.g., nuclear workers, medically-exposed, the Taiwan Co-60 exposed population
with 17 years of negligible cancer vs. Taipei residents, etc. etc.
http://cnts.wpi.edu/rsh/Data_Docs/
Regards, Jim
muckerheide@mediaone.net
========================
"Strom, Daniel J" wrote:
>
> RADSAFERs,
>
> This is top class work in a premier journal. The implications are yet to be
> understood, but suffice it to say that if sub-ionizing electrons cause double
> strand breaks (DSBs) in DNA by the mechanism shown by these researchers, then
> ionizing radiation truly differs from chemicals in its genotoxic mechanisms.
>
> Barry D. Michael and Peter O'Neill. Sting in the Tail of Electron Tracks.
> Science Mar 3 2000: 1603-1604.
>
> http://www.sciencemag.org/cgi/content/full/287/5458/1603
>
> and
>
> Badia Boudaiffa, Pierre Cloutier, Darel Hunting, Michael A. Huels, and Leon
> Sanche. Resonant Formation of DNA Strand Breaks by Low-Energy (3 to 20 eV)
> Electrons. Science Mar 3 2000: 1658-1660
>
> http://www.sciencemag.org/cgi/content/full/287/5458/1658
>
> If your library subscribes to Science, then you can get full text (and figures)
> from the above sites.
>
> The mechanism appears to be excitation of a DNA base by the electron, resulting
> in a DSB. Judge for yourself.
>
> - Dan Strom
>
> The opinions expressed above, if any, are mine alone and have not been reviewed
> or approved by Battelle, the Pacific Northwest National Laboratory, or the U.S.
> Department of Energy.
>
> Daniel J. Strom, Ph.D., CHP
> Risk Analysis & Health Protection Group, Environmental Technology Division,
> Pacific Northwest National Laboratory
> Mail Stop K3-56, PO BOX 999, Richland, Washington 99352-0999 USA
> Telephone (509) 375-2626 FAX (509) 375-2019 mailto:daniel.j.strom@pnl.gov
> Brief Resume: http://www.pnl.gov/bayesian/strom/strombio.htm
> Pagemaster for http://www.pnl.gov/bayesian http://qecc.pnl.gov
> http://bidug.pnl.gov
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