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. 2023 Dec 31;11(27):2306716. doi: 10.1002/advs.202306716

Figure 1.

Figure 1

Covalent nanobody conjugation via self‐catalyzing spyTag/spyCatcher bond. A) SAM‐based nanobody immobilization. A synthetic spyTag peptide (marked in a red box) is chemically coupled to the HDT monolayer via maleimide click chemistry. The nanobody‐spyCatcher fusion protein attaches itself to this chemical layer through the autocatalytic formation of a covalent spyTag‐spyCatcher bond. B, C) SpyDirect‐based nanobody immobilization. Direct biofunctionalization of the Au gate electrode with a cysteine‐terminated spyTag‐peptide followed by the coupling of the nanobody‐spyCatcher fusion protein. (B) SpyDirect N′ coupling. The SpyTag is immobilized through an N‐terminal cysteine. (C) SpyDirect C′ coupling. The inverted SpyTag immobilization through a C‐terminal cysteine removes steric constraints for SpyCatcher packing and linker‐nanobody arrangement.