It's about the hemerythrin and hemcyanin

It's about the hemerythrin and hemcyanin

1. Hemerythrin and Hemocyanin Deoxyhemerythrin , Oxyhemerythrin , Deoxyhemocyanin , Oxyhemocyanin

2. Hemerythrin Found in marine invertibrates (sea spider, arrow crab, brine shrimp) Non- heme protein Oxygen transporter (binds O 2 reversibly) Eight subunits with two iron centres and 113 amino acids in each subunit Invertibrate : Backbone is absent, internal skeleton is not present

3. Deoxyhemerythrin Each subunit has two Fe(II) atom connected by three bridging groups . Two are carboxylato bridging groups each from glutamate and aspartate, other one is μ - oxo group from H 2 O or OH - or O 2- ( mostly OH - ). One Fe(II) has octahedron arrangement (three histidine ) other has five coordination (two histidine). The two Fe(II) atoms are antiferromagnetic coupled by Fe-O-Fe bridge.

4. A ( μ - hydroxo ) bis ( μ - carboxylato ) diiron (II) center with vacant terminal coordination site in one iron atom Fe(II), ferrous ion is in high spin confirmed by Mossbauer and EPR spectroscopy They are colourless

5. Oxyhemerythrin High spin ferric centres One oxygen binds to two Fe(II) atom in each subunit ( oxidative addition .) No cooperative effect O 2 binds in the 6 th site of Fe atom in peroxide (O 2 2- ) form because each Fe(II) donates one electron and becomes Fe(III). Intermediate {Fe(II) Fe(III)} The Hydrogen from the μ - oxo group shifts to peroxide forming hydroperoxy group . Hydrogen bond formed between μ - oxo group (acceptor) and hydrogen group of hydroperoxy group (donor). Antiferromagnetic coupling of Fe(III) atoms so they have diamagnetic ground state Violet- pink colour.

6. Raman spectra As strength of bond increases and distance between bond decreases , Stretching band frequency increases. For oxy Hr O-O stretching vibration was 844 cm -1 , which corresponds to peroxide

7. Hemocyanin Copper protein Several subunits Oxygen carrier in invertibrates like Mollusca ( eg . Snails, squid, whelks) and Arthopoda ( eg . Crabs, lobsters, shrimps).

8. Deoxyhemocyanin It contains two Cu(I) metal , cuprous colourless molecule Each Cu(I) is bound to three histidine residues

9. Oxyhemocyanin It has two Cu(II) atom which binds one O 2 molecule Blue colour due to LMCT transition Each Cu(I) donates one electron ( oxidised to Cu(II) ) to O 2 thus oxygen gets reduced to peroxide O 2 2-

10. The two Cu(II) atoms are antiferromagnetically coupled and is diamagnetic in room temperature. Raman studies showed stretching vibration of 750 cm -1 proving the presence of ( μ - peroxo ) dicopper (II) centre.

11. References Principles Of Bioinorganic Chemistry by Stephen J. Lippard, Jeremy M. Berg Organometallic and Bioinorganic chemistry by Ajai Kumar

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