FIGURE 1.

Linkage of substrates and inhibitors of SGLT1to the AFM tip via heterobifunctional PEG linker by a three-step protocol. Thio-glc, hex-glc, and AcS-aminophlorizin (amino-phl) (A) were coupled to cross-linkers varying in lengths having a maleimide end group (∼8 nm) or an acrylamide-end group (∼30–40 nm) (B). C, amino groups were generated on the silicon nitride AFM cantilever tip using aminopropyltriethoxysilane (step 1) to attach the flexible distensible PEG-linker covalently via its NHS end to the tip (step 2). The ligand was linked to the free thio-reactive end of the PEG chain (step 3). Thioglucose was coupled to the acrylamide-linker, hexyl-glucose, and aminophlorizin were bound to the maleimide-linker. Circles in B and C indicate the thio-reactive group (TRG). In C the dotted line circles the ligand, which is coupled to the PEG linker.