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On Thu, 9 Nov 1995, A.Appleyard wrote: > > Please what is the book or scientific paper reference for this information? > This came from a textbook we're using called Biochemistry foufth edition by Lubert Stryer published in 1995. The ISBN # is 0-7167-2009-4 > > Cytochrome oxidase binds O2 in an Fe-Cu complex allowing the O2 to accept > > four electrons to produce two molecules of H2O. This is the normal pathway, > > but if O2 does not accept four complete electrons, then a Superoxide anion > > is produced. This is a very destructive compound and is the begining of O2 > > toxicity. The Superoxide anion is not produced under normal circumstances > > (except for small amounts) ... What is the direct chemical interaction that > > causes the Superoxide anion to be produced? > > If so, perhaps sometimes another O2 molecule hits the O2-Fe-Cu-cytochrome-etc > complex hard enough to knock the `sitting tenant' O2 molecule out and replace > it before it has picked up 4 electrons. This may be more likely to happen at > depth when depth pressure causes a lot of unbound oxygen in solution. > If the O2 molecule has picked up N electrons (and some protons (chemists' > word usage for H+ ions) to balance the electric charge), the result is this:- > 0 oxygen (O2) > 1 superoxide (HOO) > 2 hydrogen peroxide (HOOH) > 3 1 water and 1 free hydroxyl (OH) radical, I suppose, if this happens > 4 2 water > > There is an enzyme to turn 2 HO2 -> O2 + HOOH. > There is an enzyme to turn 2 HOOH -> O2 + HOH. > The O2 binds in the Fe-Cu complex just like it does between the Fe-His E7 in Mb and Hb. As you know this is a very strong bond. It is possible that an O2 or O-2 molecule could be knock out, but this won't yield a Superoxide anion. I noticed you labeled superoxide in your list, but the cause here is a Superoxide Anion(O2-). This is where my chemistry weakpoint comes into play. As I was checking for the difference between Superoxide and Superoxide anion I found another aside in another chenistry book. It talks about the Superoxide dimutase which protects us from the Superoxide Anion. Superoxide anion is very damaging to vital enzymes and this may contribute to the aging process so the book says. My guess is that when the tissues begin to get more O2 in them, the free electrons begin to bind to the O2 molecules and form O2-(Superoxide anion). The only reservation I have about this is that the books says that the catalyst must not release partially reduced intermediates. So if the Fe-Cu complex can release the Superoxide anion, then how is that done exactly? > > ... Are there any known cases of [mutations to the guanine in DNA] happening > > from diving high pp O2s? This has been a problem among athletes. > > What is this effect in athletes? I haven't heard of it. > I will check into this further! > > Any flames on this subject are also welcome!! > > and in a high oxygen environment will burn much hotter! > -- > Send mail for the `techdiver' mailing list to `techdiver@terra.net'. > Send subscription/archive requests to `techdiver-request@terra.net'. > Aloha Tony ANTHONY MONTGOMERY Marine Option Program Waikiki Aquarium 1000 Pope Road MSB #203 2777 Kalakaua Ave Honolulu, Hawaii 96822 Honolulu, Hawaii 96815 Fax: (808) 956-2417 Fax: (808) 923-1771 Phone: (808) 956-6000 Phone: (808) 923-9741
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