Chemical Forums
Specialty Chemistry Forums => Biochemistry and Chemical Biology Forum => Topic started by: Nebojsa on February 17, 2015, 04:12:18 AM
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I have the problem in understanding how Fe(II) releases electron and becomes Fe(III) in Boston Hemoglobin. Anyone who wants to help me can look at the pictures and understand what the problem is. I am a Medical student so I am not supposed to know such things so that is why I am asking this.
I want to know how Fe in Heme becomes oxidised after Tyrosine side chain OH- group reacts with Fe. During this oxidation the other bond with Histidine is broken so it may play some role. If you need further information dont hesitate to ask.
Looking forward to solve this problem.
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When His 58 is replaced by Tyr, the phenoxide ion (deprotonated Tyr) bonds to the iron, and kicks out His 87. The oxidised Fe3+ is stabilised by bonding to the negative ion Tyr-, compared to the neutral His.
From http://www.pnas.org/content/70/12/3870.full.pdf:
"Property: Ferric form is reduced much more slowly by
Na2S204; ferrous CO form oxidized 50 times more
rapidly by ferricyanide; ferrous oxy form
autoxidized 4.5 times.more rapidly than Rb A.
Interpretation: Reduction is opposed and oxidation favored because the
affinity of ferric iron for phenolate is higher than the
affinity of ferrous iron for imidazole."
[Ferric = Fe3+; Ferrous = Fe2+; Tyr (deprotonated) contains a phenolate=phenoxide group; His contains an imidazole group.]
I'm no biochemist, I found that just now by googling "boston hemoglobin"; I imagine even a non-chemist can do that.
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Thank you for your reply. ;D but i do not understand why Fe2+ becomes Fe3+ ?
Why Fe gets oxidised? Some oxidising agent causes that or...?
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Nebjosa,
Ordinarly, we insist that people who ask questions show their attempt first; that is a forum rule. Now mjc123 gave you a very good start, so it should be easy to make an attempt. Here is another paper to help: http://www.ncbi.nlm.nih.gov/pubmed/7755625