Mailing List Archive Mailing List Archive
A.APPLEYARD@fs*.mt*.um*.ac*.uk* wrote:- > 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 [thus > producing a superoxide ion O2-]. ... Anthony Montgomery <amontgom@ha*.ed*> replied:- > 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 > ... The sitting O2 has time to pick up one electron and become O2-, then it is knocked out of the complex. Result is one loose O2- (superoxide) ion. > in another chemistry book. It talks about the Superoxide dimutase which > protects us from the Superoxide Anion ... I think this should be `dismutase'. It turns 2 O2- + 2 H+ into O2 + HOOH. There is also a peroxide dismutase that turns 2 HOOH into O2 + 2 HOH. > the books say 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? The speeds of thermal motions of molecules are distributed on a frequency pattern, and occasionally there is one fast enough to knock the O2 out of the complex before it has received all 4 electrons to turn it into 2 HOH. Normally likely the O2 (or whatever intermediate stage it has reached) at once goes back into the complex again, but if the body fluid ppO2 is high and there is a lot of free O2 about, a different O2 molecule may get into the complex first and leave a free O2- or HOOH or HO to cause what damage it can unless the dismutase enzymes find it first.
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]