Y. Gimeno

Electrochemical and AFM characterization on gold and carbon electrodes of a high redox potential laccase from Fusarium proliferatum

The redox potential of the T1 copper site of laccase from Fusarium proliferatum was determined by titration to be about 510 mV vs. SCE (750 mV vs. NHE), which makes it a high redox potential enzyme. Anaerobic electron transfer reactions between laccase and carbon and gold electrodes were detected, both in solution and when the enzyme was adsorbed on these surfaces. In solution, a single high-potential signal (660 mV vs. SCE) was recorded at the carbon surfaces, attributable to the T1 copper site of the enzyme. However, a well-defined oxidative process at about 660 mV and an anodic wave at 350 mV vs. SCE were recorded at the gold electrode, respectively associated with the T1 and T2 copper sites. Laccase-modified carbon electrodes behaved analogously when the enzyme was in solution, unlike laccase adsorbed on gold, which showed only a low-potential signal. Laccase molecules were successfully imaged by AFM; obtaining a thick compact stable film on Au(111), and large aggregates forming a complex network of small branches leaving voids on the HOPG surface. Laccase-modified carbon electrodes retained significant enzymatic activity, efficiently oxidising violuric acid and reducing molecular oxygen. Explanations are proposed for how protein-film organisation affects the electrode function.

Metal patterned highly oriented pyrolytic graphite as a template for direct polymer molding

Fractal Pd islands have been used to demonstrate that a metal patterned highly oriented pyrolytic graphite (HOPG) is a suitable template for direct molding of cavities and channels on elastomeric polymeric materials. Due to the low reactivity of the surface the method requires neither substrate surface modification nor subsequent steps so that it is very simple and inexpensive. Features larger than 20 nm in size can be easily transferred from the template to the mold. Damage was observed neither in the patterned polymeric material nor in the HOPG template after release of the polymer film.