Chemistry Reference
In-Depth Information
TABLE 3.7. Reaction Rate Constants for Consumption of Chlorine Dioxide by
Amino Acids and Peptides
Compound
pH
Temp (°C)
Reference
k
(/M/s)
gly
8.0
22-24
<10
−5
[152]
Pro
6.0
25.0
3.4 × 10
−2
[155]
OH-Pro
6.0
25.0
6.9 × 10
−2
[155]
5.4 × 10
−2
His
6.0
25.0
[155]
Cys
7.0
25.0
1.0 × 10
7
[163]
Tyr
7.0
25.0
1.8 × 10
5
[163]
N
-Acetyl-Tyr
6.2
25.0
3.2 × 10
4
[168]
Trp
7.0
25.0
3.4 × 10
4
[171]
gSH
5.9
25.0
5.8 × 10
2
[163]
NADH
6-8
24.6
3.9 × 10
6
[170]
14
12
10
8
Cys
6
4
2
GSH
0
3.0
3.5
4.0
4.5
5.0
5.5
6.0
pH
Figure 3.16.
Effect of pH on the second-order rate constants for the oxidation of Cys
and gSH by ClO
2
at 25°C (data were taken from Ison et al. [163]).
The oxidation of thiols (Cys and gSH) by ClO
2
as a function of pH has
been performed [163, 164]. The rate constant for Cys and gSH increased with
an increase in pH from 3.2 to 5.9 (Fig. 3.16) [163]. The pH-dependence behav-
ior suggests the deprotonated species of thiols were the reactive species. The
solid fitted lines of the experimental results gave rate constants for the reac-
tions of ClO
2
with the cysteinyl anion (CS
−
) and the glutathione anion (gS
−
)
Search WWH ::
Custom Search