| Abstract [eng] |
In this work bioelectrocatalytic functions of multicopper oxidases adsorbed on gold nanoparticles are studied. As multicopper oxidases, laccases and human ceruloplasmin are used. The enzymes have been employed in electrochemical systems consisting of gold electrodes covered by gold nanoparticles and enzymes. For the first time direct electron transfer between gold nanoparticle and active centre of laccase has been reported. Laccases from Trametes hirsuta and Trichaptum abietinum, also human ceruloplasmin, exhibited direct electron transfer between active centres of the enzyme and gold nanoparticles, meanwhile the laccases exhibited efficient direct electron transfer based oxygen bioreduction on electrode surface. Heterogeneous electron transfer speed in gold nanoparticle - laccase bioelectrocatalytic systems depended on nanoparticle size. In general, larger diameter (60 – 90 nm) gold nanoparticle systems exhibited slower oxygen bioreduction than medium sized (40 – 50 nm) gold nanoparticle systems. Heterogeneous electron transfer constants reached as high as 45 s-1 and 11 s-1 in Trichaptum abietinum and Trametes hirsuta laccase systems, respectively. Direct electron transfer between laccase and gold nanoparticles mechanism has also been studied. It was discussed that T1 site is not detectable at gold nanoparticle surface. Several changes of Trichaptum abietinum laccase catalytic properties upon adsorption on gold nanoparticles have been revealed. It was discussed that probably the optimum curvature of gold nanoparticles are responsible for formation of most efficient direct electron transfer based bioelectrocatalytic systems. |
