Oxygen Coordination in Myoglobin and Hemocyanin
The binding of molecular oxygen ($O_2$) to metalloproteins like myoglobin and hemocyanin results in the oxygen existing in specific reduced forms coordinated to the metal ion.
Oxy-Myoglobin
In oxy-myoglobin, the heme iron atom is typically in the Fe(III) oxidation state. The bound oxygen molecule is reduced to the superoxide form ($O_2^-$).
The interaction can be represented as:
Fe3+ + $O_2^-$
Oxy-Hemocyanin
In oxy-hemocyanin, the active site contains two copper ions. When oxygen binds, it is reduced to the peroxide form ($O_2^{2-}$), bridging the two Cu(II) ions.
The interaction can be represented as:
2Cu2+ + $O_2^{2-}$
Conclusion
Therefore, the $O_2$ coordinated to metal ion centres in oxy-myoglobin and oxy-hemocyanin exists, respectively, as superoxide and peroxide.
Important Questions from Bioinorganic Chemistry
Consider the following transformation reactions in the context of co - enzyme B12
A. 1, 2 - Carbon shift
B. Hydration of CO2
C. Benzene to phenol
D. Dimethyl sulfide to dimethyl sulfoxide
The correct statement(s) for co - enzyme B12 is / are
During the binding of O2 to myoglobin (consider 'heme' in xy-plane), the molecular orbital of O2 and atomic orbital of Fe involved in the formation of the σ-bond is
In the catalytic cycle of Cytochrome P450, the generation of [(porphyrin)+•FeIV(O)] from [(porphyrin)FeIII(OOH)] involves
Match List I with List II
List I
List II
Metalloprotein
Metal
A.
carboxypeptidase A
I.
Mn
B.
oxygen-evolving complex
II.
Fe
C.
hemerythrin
III.
Ni
D.
coenzyme F-430
IV.
Zn
Choose the correct answer from the options given below:
In solution, Vaska's complex is known to bind O2 reversibly. In the product, oxidation state of the metal ion center coordination geometry and mode of binding of O2, respectively are
