Xh. Chen et al., Characterization of the direct electron transfer and bioelectrocatalysis of horseradish peroxidase in DNA film at pyrolytic graphite electrode, ANALYT CHIM, 412(1-2), 2000, pp. 89-98
Direct electron transfer between horseradish peroxidase (HRP) in a DNA film
and pyrolytic graphite (PG) electrode was observed at the formal potential
of -0.208 V (versus Ag/AgCl (sat. KCI)) involving the Fe-III/Fe-II redox c
ouple. DNA played the role of charge carrier and facilitated the electron t
ransfer between HRP and the PG electrode. The peak current of the redox pro
cess increased linearly with scan rate from 0.05 to 2 V/s, which is typical
in thin layer electrochemistry. The number of electrons and the average ap
parent heterogeneous electron transfer rate constant k(s) involved in the r
edox reaction were calculated to be 0.94 and 1.130 s(-1), respectively. The
formal potential dependence on pH with 54 mV per pH indicated a one-proton
-transfer coupled with a one-electron-transfer reaction. Scanning electron
microscopy (SEM) showed the different morphologies for isolated DNA film an
d the complex film of HRP and DNA. Visible absorption and reflectance-absor
ption infrared (RAIR) spectra proved the heme environment of HRP in DNA fil
m to be in its native status. The embedded HRP molecules in DNA him retaine
d the electrocatalytic activity for hydrogen peroxide. The sensitivity of t
he HRP-DNA-PG biocomposite was 115.6 mu A/cm(2) for 2.5 x 10(-4) mol/l H2O2
. This HRP-DNA film modified PG electrode represented a valid example of me
diator-free amperometric biosensors. (C) 2000 Elsevier Science B.V. All rig
hts reserved.