Bionanoconjugates of the enzyme tyrosinase (TYR) and gold nanoparticles (AuNPs) functionalised with a peptide (CALNN) were produced in solution and characterised. The formation of stable TYR-AuNP:CALNN bionanoconjugates (BNCs) was supported by a decrease of the surface charge of the BNCs as determined by f-potential and an increase in hydrodynamic diameter as determined by Dynamic Light Scattering (DLS). UV/Vis studies of pH-induced aggregation revealed distinct protonation patterns for the BNCs when compared with AuNP:CALNN alone, further substantiating BNC formation. Activity studies of the BNCs for the reduction of di-phenols in solution indicated that TYR not only remains active after conjugation, but interestingly its activity in the BNCs is higher than for the free enzyme. In conclusion, AuNP:CALNN can provide a suitable platform for the immobilisation of TYR, leading to BNCs with increased enzyme activity and a wider pH working range, with promising uses in electrochemical biosensors for the detection of mono-and di-phenolic compounds.
Studies were done to learn the role of some factors (nature of substrate, thickness of polymeric layer, presence of ller in the polymer) in the oxidation (the consumption rate of the antioxidant, the induction period) and adhesion strength (resistance to separation of coating from the substrate) of stabilized PE coatings.These factors lead to local zones in the coatings (in the polymer layer in contact with catalytically active substrates, near the ller particles, and in the outermost surface layer of the coatings oxidized under the conditions where oxygen was supplied by the diffusion mechanism) in which the antioxidant was consumed at an increased rate. The antioxidant consumed in these zones is replenished diffusively from the remaining part of the coating. A correspondence was observed between the induction period for oxidation of the polymer layer in contact with the substrate and the induction period for attaining adhesion (bonding) of the coating.
ABSTRACT:The amine antioxidant, Neozon D, was treated to increase its effectiveness in suppressing oxidation of polyethylene in contact with copper. It was found that this antioxidant becomes more efficient after interaction with a copper substrate. These experimental results show that the role of substrate is to catalyze oxidation transformations in the antioxidant.
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