Effects of glutamate dehydrogenase enzyme on the SERS spectra of nicotinamide adenine dinucleotide on a gold electrode

摘要

Near-infrared Fourier transform Raman spectroscopy was used to study the SERS behaviors of nicotinamide adenine dinucleotide (NAD) in a solution containing Glutamate dehydrogenase enzymes. It was found that the SERS spectra of NAD adsorbed on a gold electrode should be largely changed by addition of glutamate dehydrogenase (GDH) in the electrolyte solutions. The potential dependence of the SERS revealed that, in an adequate negative potential region, NAD adsorbed on a gold electrode can be combined with the enzyme to a certain extent. The SERS spectra of NAD/GDH exhibit some different properties from those shown for normal SERS spectra of NAD alone in two aspects: (1) The existence of the enzymes led to decrease or disappearance of several strong bands under open circuit conditions. The reductions of the SERS bands are quite consistent with the changes of normal Raman spectra of NAD in combination with some NAD-dependent dehydrogenase in solutions. The protonation of the adenine moiety was proposed to explain this SERS behavior. (2) Several new bands, some of which can be attributed to the backbone peptide of the enzyme, appeared and increased in intensity with a negative shift of the electrode potential. The appearance of the new bands was attributed to the close approach of the active site of the enzyme induced by the coenzyme preadsorbed on the surface. [References: 44]