Xref: utzoo sci.bio:2342 sci.chem:499 sci.med:12483 Path: utzoo!attcan!uunet!mcsun!ukc!edcastle!djm From: djm@castle.ed.ac.uk (D Murphy) Newsgroups: sci.bio,sci.chem,sci.med Subject: Re: Butane death Message-ID: <469@castle.ed.ac.uk> Date: 22 Sep 89 08:58:23 GMT References: <89262.194442RAV103@PSUVM.BITNET> <3398@kitty.UUCP> <4633@ursa-major.SPDCC.COM> Reply-To: djm@castle.ed.ac.uk (D Murphy) Organization: Edinburgh University Chemistry Lines: 29 In article <4633@ursa-major.SPDCC.COM> dyer@ursa-major.spdcc.COM (Steve Dyer) writes: > >I had always understood that methemoglobin is simply an oxidized form >of hemoglobin, with the ferrous iron (Fe++) in heme oxidized to the >ferric (Fe+++) state. I don't see where methane comes in. Methane >certainly isn't one of the traditionally-enumerated toxic agents which >cause methemoglobinemia, such as nitrites and certain aromatic amines. > >-- >Steve Dyer No. There is no iron oxidation in the hemoglobin - oxyhemoglobin reaction. If there were there would be significant risk of Fe(III) precipitation in the (mildly) alkaline blood. What happens is that the first oxygen (there are 4 heme units per molecule) complexes with the Fe(II) in one of the hemes, causing it to move slightly out of the plane of the heme. This causes a small conformational change which assists the uptake of an oxygen molecule by the next heme and so on until all 4 are occupied. The reverse is also true - oxygen release is facilitated by the conformational change when one heme releases its O2. What's more, the oxygen remains intact. If the iron oxidized, oxygen radicals would be produced which would do lots of damage. Also, a lot of energy would likely be required to bring about release of O2 at the tissues. Murff...