Chemistry Reference
In-Depth Information
Zn(II) is not redox-active in biological environment but becomes active
in coordination environment when complexed with thiolate ligand. Further-
more, the coordination environment of the complexes critically control the
availability of Zn [75]. The speciation study on Zn(II)-GSH (H
3
G) and
Zn(II)-
N
-acetylcysteineglycine (NaACCG, H
2
L) suggested only mononuclear
species, [ZnL], [
ZnL
2−
], [ZnL
3
]
4−
, [ZnL
2
H
-1
]
3−
, [ZnL
2
H
-1
]
3−
, and [ZnL
2
H
-2
]
4−
[118]. However, nine species in the Zn(II)-GSH system were reported
(Fig. 2.6a), which include both mononuclear and binuclear species under the
(a)
100
Zn
2+
[ZnG
2
H
-2
]
6-
80
[ZnG
2
H
-1
]
5-
60
[ZnG
2
H]
3-
[ZnG]
-
40
[ZnG
2
]
4-
[ZnG
2
H
2
]
2-
20
[ZnGH]
0
4
5
6
7
8
9
10
11
pH
(b)
1.0
ZnL
2-
ZnH
-1
L
3-
3.812
δ
GlyH
1
3.6
0.5
3.808
δ
Zn
2
L
α
-Glu
ZnHL
-
3.3
3.804
0.0
5
6
7
8
9
10
pH
Figure 2.6.
(a) Distribution diagram for the Zn
2+
/GSH (H
3
G) system (Zn : G = 1.0 : 1.81,
C
Zn
= 1.6 × 10
−3
M):
= [Zn
2
L
2
H
−1
]
3−
;
= [Zn
2
L
2
H
−2
]
4−
(adapted from Ferretti et al.
[118] with the permission of the Elsevier Inc.). (b) The species distribution for
Zn(II)−GSSG complexes, calculated for the conditions of NMR experiments (10 mM
GSSG, 10 mM Zn(II), 25°C). Chemical shifts of α-Glu and GlyH
1
are overlaid for
comparison (adapted from Krezel et al. [120] with the permission of the American
Chemical Society). See color insert.
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