Supramolecular-mediated immobilisation of L-phenylalanine dehydrogenase on b-cyclodextrin-modified gold nanospheres

Native and adamantane-modified L-phenylalanine dehydrogenase was immobilised on b-cyclodextrin coated gold nanospheres via supramolecular associations. The amount of immobilised protein was estimated to be about 100–110mg per milligram of support. The nanocatalyst retained high catalytic activity and showed increased affinity for the substrate. Both immobilised enzymes showed fluorescence emission spectra similar to that of the native protein counterpart. The range of optimum pH for catalytic activity was increased from 11.5 to 11.5–12.5 for the native and adamantane-modified enzymes after adsorption on gold nanospheres. Immobilised native and modified L-phenylalanine dehydrogenase retained about 20 % and 41%, respectively, of the initial activity after 10 cycles of reuse. These results open a new perspective to the possible application of cyclodextrin-modified gold nanospheres as water-soluble carriers for enzyme immobilisation