Comparative Characterization of Peanut β-Amylase Immobilization onto Graphene Oxide and Graphene Oxide Carbon Nanotubes by Solid-State NMR

In this Article, we describe solid-state NMR experiments on a model biocatalyst system consisting of the enzyme β-amylase covalently immobilized on graphene oxide nanosheets (GO) and graphene oxide–carbon nanotube composites (GO–CNT). One-dimensional magic angle spinning (MAS) NMR technique was employed on carbon nuclei (13C) in natural abundance. The support systems (GO and GO–CNTs) were characterized first, and it was possible to assign carbon species. The difference in the 13C spectrum between GO and GO–CNT indicated that CNT rods were successfully incorporated within GO sheets, producing sharp peaks. The shifts in the spectrum of enzyme-immobilized support systems indicated immobilization. Many more changes were observed in the 13C MAS NMR spectra during the immobilization process, which arose from cross-linking of the surface carbon species via glutaraldehyde with the amino group of enzyme. This study showed the potential of natural abundance 13C MAS NMR for comparative characterization of the two na...