Enzymatic Methane Hydroxylation: sMMO and pMMO
51
OH 2
Fe
O
OH 2
OH 2
Fe
O
O
O
C
H
C
H
H
H
H
H 2 O
Fe
C
H
H
H
H
Fe
C
H
H H
Relative Energy (eV)
L
L (Å)
H
T d -Methane
C 3v -Methane
C 3v -Methane
T d -Methane
-0.3
0.0
0.3
0.6
0.9
1.2
2
2.2
2.4
2.6
2.8
3
3.2
3.4
3.6
OH 2
Fe
O
OH 2
OH 2
Fe
O
O
O
C
H
C
H
H
H
H
H 2 O
L
Relative Energy (eV)
L (Å)
T d -Methane
=
Fe
C
=
H
H
H
H
D 2d -Methane
-0.3
0.0
0.3
0.6
0.9
1.2
2
2.2
2.4
2.6
2.8
3
3.2
3.4
3.6
OH 2
Fe
O
OH 2
OH 2
Fe
O
O
O
C
H
H 2 O
CH 4
(a)
(b)
(c)
Fig. 3 a Interaction between CH 4 and coordinatively unsaturated diiron active site of MMOH Q
with a nonbonding orbital in its frontier orbital region. b total energy diagrams (from extend Hückel
calculations) for the coordination of T d - and C 3v -type methanes to a coordinatively unsaturated
diiron active site of MMOH Q as a function of the separation between the iron and methane carbon
atoms (L). Similar energy diagram in the D 2d -type methane case can be seen in (c). Reprinted with
the permission from Ref. [43]. Copyright 1997 American Chemical Society