2
666 Jiao et al.
Asian J. Chem.
2.07 (m, 2 H), 2.00 (s, 3 H), 1.88 (s, 6 H),1.71 (s, 6 H)). UV-
was investigated using ethanol, DMSO, DMF, CH CN, as co-
3
visible spectra were obtained using a Shimadzu 2600 UV-
visible-NIR spectrophotometer. The buffer pH values were
determined with a METTLER TOLEDO 320 pH meter.
Determination of glutathione peroxidase activity in
solvent mixture of PBS and co-solvents: The catalytic activity
was assayed according to a modified method reported by
Hilvert and Wu . The typical assay process of glutathione
peroxidase activity in solvent mixture of PBS and ethanol was
shown as follows: The reaction was carried out at 25 °C in a
solvents, respectively. Typically, the catalytic activity ofADA-
Te-OH for the reduction of hydroperoxide by 3-carboxyl-4-
nitrobenzenethiol was evaluated according to the modified
method reported by Hilvert and Wu using 3-carboxyl-4-
nitrobenzenethiol as a glutathione (GSH) alternative (Fig. 1).
11
Compared with the traditional small molecule artificial
11
-1
glutathione peroxidase PhSeSePh (ν
0
= 0.019 µM min ), a
remarkable rate enhancement was observed whenADA-Te-OH
was used as artificial glutathione peroxidase under the condi-
tions of different solvent mixture (Table-1). This observation
proved that ADA-Te-OH exhibited more excellent catalytic
ability than traditional PhSeSePh. Additionally, the highest
catalytic rates were observed when different co-solvents were
used (Table-1).
1
mL quartz cuvette, 700 µL solvent mixture of PBS and
ethanol and 100 µL of ADA-Te-OH (0.025 mM) were added
and then 100 µL of the 3-carboxyl-4-nitrobenzenethiol solution
(
1 mM) was added. The mixture in the quartz cuvette was pre-
incubated at the 25 °C for 3 min. Finally, the reaction was
initiated by the addition of 100 mL of hydroperoxide (2 mM)
and the absorption decrease of 3-carboxyl-4-nitrobenzenethiol
TABLE-1
-1
-1
INITIAL RATES (ν ) AND ACTIVITIES FOR THE REDUCTION
at 410 nm (ε410 = 13600 M cm . pH = 7.0) was monitored
using a Shimadzu 2600 UV-visible-NIR spectrophotometer.
Appropriate control of the non-enzymatic reaction was
performed and was subtracted from the catalyzed reaction.
The glutathione peroxidase activities in solvent mixture of PBS
and other co-solvents were assayed similarly except ethanol
was replaced by other co-solvents.
0
OF CUOOH (2 mM) BY 3-CARBOXYL-4-NITROBENZENETHIOL
(
1 mM) IN THE PRESENCE OF THE ADA-Te-OH (0.025 mM)
AT pH 7 AND 25 °C
-1
a
Co-solvent
PBS:co-solvent (v:v)
ν (mM min )
0
Ethanol
DMSO
DMF
6:4
7:3
7:3
6:4
2.23 ± 0.12
2.05 ± 0.08
1.67 ± 0.15
1.57 ± 0.08
Determination of the glutathione peroxidase catalytic
rates influenced by co-solvents: Typically, the volume ratios
of PBS:ethanol used in the determination of the glutathione
peroxidase catalytic rate were shown as follows: 9:1; 8:2; 7:3;
CH CN
3
a
Initial rate of reaction was corrected for the spontaneous oxidation.
And the concentration of catalyst is 0.025 mM and assuming one
molecule catalytic center (tellurium moiety) as one active site of
enzyme
6
:4; 5:5; 4:6; 3:7; 2:8; 1:9. The catalytic activities influenced
by other co-solvents were assayed similarly except ethanol
was replaced by other co-solvents.
Determination of the glutathione peroxidase catalytic
rate influenced by co-solvent: Herein, the solvent mixture
consisted of PBS and co-solvent was employed as assay solu-
tion to determine the glutathione peroxidase catalytic rate. The
ratio of PBS to co-solvent was fixed to 9:1; 8:2; 7:3; 6:4; 5:5;
RESULTS AND DISCUSSION
Determination of the glutathione peroxidase catalytic
activity ofADA-Te-OH: Herein, to reveal the relation between
the catalytic rate of artificial glutathione peroxidase and the
property of solvent mixture, ADA-Te-OH was selected as the
typical hydrophobic artificial glutathione peroxidase (shown
in Fig. 1). Typically, the structure of ADA-Te-OH was illus-
trated in Fig. 1. It was clearly shown that several hydrophobic
groups are presented in ADA-Te-OH, such as adamantane,
4:6; 3:7; 2:8,1:9, respectively. Typically, glutathione peroxidase
catalytic rate influenced by increasing added ethanol was
investigated (Fig. 2 a). From Fig. 2 a, we noted that the catalytic
rate of ADA-Te-OH increased to some extent with ethanol
-1
increasing added. And the highest value (2.23 µM min ) was
obtained when the volume ratio was 6:4. However, the catalytic
reaction rate largely went down when the volume ratio increased
further. Additionally, the similarly catalytic behaviours were
-
TeCH
2
2
-, -CH -, etc. Therefore, the solubility of ADA-Te-OH
3
also observed when DMSO, DMF and CH CN were used as
co-solvents based on Fig. 2 b, c, d.
in water was poor. Thus, the catalytic property ofADA-Te-OH
Fig. 1. Determination of glutathione peroxidase catalytic rates of ADA-Te-OH for the reduction of hydroperoxide using 3-carboxyl-4-nitrobenzenethiol as substrate
Jiao
