A GFET Nitrile Sensor Using a Graphene‐Binding Fusion Protein

Abstract

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). 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. 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 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 . 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). 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.

Self-assembled GA-Repeated Peptides as a Biomolecular Scaffold for Biosensing with MoS2 Electrochemical Transistors

“…Electrical detection of the target molecules with transistor-based biosensors is currently a ubiquitous mechanism for biosensing. To enhance the transistor-based biosensors’ sensitivity, nanomaterials such as Si nanowires and carbon nanotubes are often used for the detection-channel part of the transistor because of their high specific surface area. − More recently, biosensors with two-dimensional (2D) nanomaterials represented by graphene and MoS 2 have demonstrated a high sensitivity to a variety of target molecules. − While graphene is semi-metallic, MoS 2 is a new member of the 2D materials with a semiconducting property, allowing for higher electrical sensitivity for biosensing, in principle, than graphene biosensors …”