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Re: algae, H2O2, SOD, et al.

Karla had a slow morning, so she wrote up a few more thoughts regarding the H2O2 and barley straw discussion. 

I won't even *try* to translate this into something common folk like me can 
understand, other than to note that SOD stands for "superoxide dismutase". 

Karla sez:

You realize it has been 9 years since I did this stuff . . .
Superoxide is O2 with a full negative charge and an extra electron so it is
deisgnated as O2- with a dot above the -.

There are other oxygen free radicals such as hydroxyl radical (.OH).  Damage
from free radicals is the current rage in anti-aging vitamins and
supplements to fight free radicals - vit C, vit E, selenium.  People feel
that by protecting from free radicals they will protect organs from aging. -

There are some prokaryotes that do not have SOD available and thus are
susceptible to damage by superoxide, e.g. fungus.  That is what allows your
white blood cell respiratory burst to produce superoxide, hydrogen peroxide
and ultimately HOCl to kill off infectious agents and not hurt you too
badly.  We have catalase and SOD to protect us from hydrogen peroxide and
superoxide but the white blood cells do eventually succomb and form the pus
that is evident in infection.

Since the rotting of the straw prevents algae from developing, but doesn't
affect the growth of fish or higher plants, I figured that algae must lack
the protective mechanisms against oxyradicals such as catalase and SOD found
in higher organisms.  Since I don't know plant physiology, I do not know
what enzymes algae may have for defending against oxyradicals.

If you want to start some more chatting you might bring up the subject of
reactive nitrogen species which have been shown to cause damage to cells.
In fact recently nitric oxide has been shown to cause some of the biological
effects that were originally credited to oxyradicals.  Rotting straw could
certainly generate some of those from nitrogenous waste.

Karla Booth in Ft. Collins, Colorado (booth at frii_com)