Fig. 2: Design and characterization of the biofunctionalized gold electrode. | Nature Biomedical Engineering

Fig. 2: Design and characterization of the biofunctionalized gold electrode.

From: Rapid single-molecule detection of COVID-19 and MERS antigens via nanobody-functionalized organic electrochemical transistors

Fig. 2

a, Annotated sequence of the recombinant fusion protein combining a nanobody recognition module (blue) with the SpyCatcher domain (brown), with an intervening flexible linker (dashed line). b, Structural model of the complete biorecognition layer assembled from HDT and SpyTag (chem-SAM) and nanobody–SpyCatcher fusion protein (bio-SAM) (based on PDB structures 4MLI and 3OBO). Unstructured, flexible linker regions are indicated by dashed lines drawn to scale. c, High-resolution S 2p XPS spectra of the gold electrode recorded after immobilization of the HDT layer, SpyTag peptide and nanobody–SpyCatcher protein (BSA added to the biofunctionalization solution). Spectra for the three functionalization steps are shifted vertically for clarity. d, QCM-D profile for the coupling of the SpyTag peptide and nanobody–SpyCatcher fusion protein (without BSA) in real time, starting from an HDT-coated gold electrode.

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