5.4 Protein Surface Modification
99
-30
0
30
60
90
120
150
-0.4 -0.2
0
0.2 0.4 0.6
j /
µA cm −2
E / V vs. Ag|AgCl (sat. KCl)
(A)
M450Q
-30
0
30
60
90
120
150
-0.4 -0.2
0
0.2 0.4 0.6
j /
µA cm −2
E / V vs. Ag|AgCl (sat. KCl)
(B)
M578Q
-30
0
30
60
90
120
150
-0.4 -0.2
0
0.2 0.4 0.6
j /
µA cm −2
E / V vs. Ag|AgCl (sat. KCl)
(C)
M301Q
-100
0
100
200
300
-0.2
0
0.2
0.4
0.6
j /
µ A cm −2
E / V vs. Ag|AgCl(sat.KCl)
(D)
M450QΔ1c_FDH
M450QFDH
Δ1c_FDH
FDH
Fig. 5.4 A–C Cyclic voltammograms of d-fructose oxidation at (broken line) a native FDHadsorbed Au electrode and (solid lines). A M450Q, B M578Q, and C M301Q mutant-adsorbed
Au electrodes in a McIlvain buffer (pH 4.5) containing 0.1 M d-fructose under anaerobic conditions at a scan rate of 10 mV s −1 . The dotted lines indicate background voltammograms at bare Au
electrodes. D Linear sweep voltammogram of d-fructose oxidation at the (native) r_FDH- (dashed
gray line), M450QFDH- (dashed black line), (gray line), and M450Q
line) adsorbed electrodes in a McIlvain buffer (pH 4.5) in the presence of 0.2 M d-fructose under
anaerobic conditions at v = 10 mV s −1 . The dotted line indicates the background at the bare Au
electrode. Reproduced from Refs. [19, 36] copyrights (2016) and (2019) from Elsevier and The
Electrochemical Society of Japan, respectively
Thiol-gold bonds are frequently used to assemble films on Au electrodes. Therefore, the introduction of a Cys residue at the N- or C-terminus of the enzyme
peptide chain facilitates the oriented immobilization of the enzyme [44]. Recombinant laccases (r_Lac) with a Cys-6 × His (Cys-6 × His) tag at the N- or C-terminus
were purified, and the recombinant laccase was assembled with suitable orientation
on a gold electrode via Au–S bonds (Fig. 5.5) [20]. The orientation-dependent noncatalytic DET reaction of laccase was investigated. DET-type bioelectrocatalysis
toward O 2 reduction were also investigated, but the waves were rather different from
those expected from the non-catalytic waves. The similar method was also utilized
99
-30
0
30
60
90
120
150
-0.4 -0.2
0
0.2 0.4 0.6
j /
µA cm −2
E / V vs. Ag|AgCl (sat. KCl)
(A)
M450Q
-30
0
30
60
90
120
150
-0.4 -0.2
0
0.2 0.4 0.6
j /
µA cm −2
E / V vs. Ag|AgCl (sat. KCl)
(B)
M578Q
-30
0
30
60
90
120
150
-0.4 -0.2
0
0.2 0.4 0.6
j /
µA cm −2
E / V vs. Ag|AgCl (sat. KCl)
(C)
M301Q
-100
0
100
200
300
-0.2
0
0.2
0.4
0.6
j /
µ A cm −2
E / V vs. Ag|AgCl(sat.KCl)
(D)
M450QΔ1c_FDH
M450QFDH
Δ1c_FDH
FDH
Fig. 5.4 A–C Cyclic voltammograms of d-fructose oxidation at (broken line) a native FDHadsorbed Au electrode and (solid lines). A M450Q, B M578Q, and C M301Q mutant-adsorbed
Au electrodes in a McIlvain buffer (pH 4.5) containing 0.1 M d-fructose under anaerobic conditions at a scan rate of 10 mV s −1 . The dotted lines indicate background voltammograms at bare Au
electrodes. D Linear sweep voltammogram of d-fructose oxidation at the (native) r_FDH- (dashed
gray line), M450QFDH- (dashed black line), (gray line), and M450Q
line) adsorbed electrodes in a McIlvain buffer (pH 4.5) in the presence of 0.2 M d-fructose under
anaerobic conditions at v = 10 mV s −1 . The dotted line indicates the background at the bare Au
electrode. Reproduced from Refs. [19, 36] copyrights (2016) and (2019) from Elsevier and The
Electrochemical Society of Japan, respectively
Thiol-gold bonds are frequently used to assemble films on Au electrodes. Therefore, the introduction of a Cys residue at the N- or C-terminus of the enzyme
peptide chain facilitates the oriented immobilization of the enzyme [44]. Recombinant laccases (r_Lac) with a Cys-6 × His (Cys-6 × His) tag at the N- or C-terminus
were purified, and the recombinant laccase was assembled with suitable orientation
on a gold electrode via Au–S bonds (Fig. 5.5) [20]. The orientation-dependent noncatalytic DET reaction of laccase was investigated. DET-type bioelectrocatalysis
toward O 2 reduction were also investigated, but the waves were rather different from
those expected from the non-catalytic waves. The similar method was also utilized