![]() ![]() The emerging field of bioelectronics has helped integrate electronic circuits into biological systems and provide an analytical tool for assessing physiological and pharmaceutical biomarkers. Not only do these results offer a single-step route to GFET modification, but they also present new opportunities in the biocatalytic synthesis of primary amines from nitriles. Density functional theory analysis of QueF's catalytic cycle with BnCN shows similar transition-state barriers to preQ 0, but differences in the formation of the initial thioimidate covalent bonding (∆ G ‡ = 19.0 kcal mol −1 for preQ 0 vs 27.7 kcal mol −1 for BnCN) and final disassociation step (∆ G = −24.3 kcal mol −1 for preQ 0 vs ∆ G = +4.6 kcal mol −1 for BnCN). The fusion protein has a 6.3-fold increase in binding affinity for benzyl cyanide (BnCN) versus wild-type QueF and a 1.4-fold increase for affinity for the enzyme's natural substrate preQ 0. Atomic force microscopy and analysis using a quartz crystal microbalance show that both the oligopeptide and the fusion protein incorporating it form a single adlayer of monomeric enzyme on graphene. The biological recognition element is a fusion protein consisting of nitrile reductase QueF from Escherichia coli with an N-terminal self-assembling and graphene-binding dodecapeptide. A new route to single-step and non-covalent immobilization of proteins on graphene is exemplified with the first biosensor for nitriles based on a graphene field-effect transistor (GFET). ![]()
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