52
T. Yumura et al.
Fe
Fe
OH 2
O
O
H 2 O
O
O
OH 2
H 2 O
C
H
Fe
Fe
O
O
O
O
O
OH
OH
HO
H
C
Fe
Fe
O
O
O
O
O
O
O
O
C
C
H
N
NH
HN
N
H
O
H
O
Siegbahn group
H
H
H
O
H
H
O
H
H
Fe
Fe
O
O
O
O
O
O
O
O
H
C
C
H
N
NH
HN
N
H
O
H
O
Fe
Fe
OH 2
O
O
H 2 O
O
O
O
O
NH 2
H 2 N
H
C
C
H
Fe
Fe
O
O
O
O
O
O
O
O
H
C
C
H
N
NH
HN
N
H
O
H
O
Fe
Fe
O
O
H 2 O
O
O
OH 2
H 2 O
C
H
Fe
Fe
O
O
O
O
O
O
O
O
HC
C
H
N
NH
HN
N
HC
O
H
O
H
H
O
Fe
Fe
O
O
O
O
O
O
O
O
C
C
N
NH
HN
N
CH 3
O
CH 3
O
H
H
R
O
CH 3
CH 3
R
Fe
Fe
O
O
O
O
O
O
O
O
C
C
N
NH
HN
N
CH 3
O
CH 3
O
H
H
H 3 C
O
CH 3
CH 3
CH 3
Morokuma group
Friesner group
R =
H
N
OH
O
O
Fe
Fe
O
O
O
O
O
O
C
C
N
NH
HN
N
CH 3
O
H 3 C
O
CH 3
CH 3
CH 3
Yoshizawa group
Fe
Fe
O
O
O
O
O
O
O
O
C
C
N
NH
HN
N
CH 3
O
CH 3
O
H
H
H 3 C
O
CH 3
CH 3
CH 3
Fe
Fe
O
O
O
O
O
O
C
C
N
NH
HN
N
CH 3
O
H 3 C
O
CH 3
CH 3
CH 3
H
Fe
Fe
O
O
O
O
O
O
O
O
C
C
N
NH
HN
N
CH 3
O
H 3 C
H
H
H 3 C
O
CH 3
CH 3
CH 3
H
O
H
Fe
Fe
O
O
O
O
O
O
O
O
C
C
N
NH
HN
N
CH 3
O
CH 3
O
H
H
H 3 C
O
CH 3
CH 3
CH 3
H
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
(k)
(l)
(m)
(n)
(o)
(p)
Fe
Fe
O
O
O
O
O
O
O
O
C
C
N
NH
HN
N
CH 3
O
CH 3
O
H
H
H 3 C
O
CH 3
CH 3
CH 3
Fig. 4 Various diiron models of MMOH Q used in literatures. Models of (a) and (b) were taken
from Ref. [46], that of (c) from Ref. [52], those from (d) to (j) from Ref. [56], that of (k) from Ref.
[57], that of (l) from Ref. [59], that of (m) from Ref. [63], that of (n) from Refs. [66] and [68], that
of (o) from Ref. [74], and that of (p) from Refs. [77] and [83]
at 2000 [76, 77] who used models labeled as (n) and (p) in Fig. 4, respectively. The
diiron models used after 2000 (Fig. 4c–j, l, m, o, p) contain ligands more realistic to
mimic actual glutamate and histidine residues [52, 53, 56, 59, 63, 74]. The improvement, where the first coordination sphere around the diiron active site was reasonably
modeled, increased the reliability of data obtained from DFT calculations, such as