Anchoring of Histidine‐Tagged Proteins to Molecular Printboards: Self‐assembly, Thermodynamic Modeling, and Patterning

In this paper the multivalent binding of hexahistidine (His 6 )‐tagged proteins to β‐cyclodextrin (β‐CD) self‐assembled monolayers (SAMs) by using the nickel(II) complex of a hetero‐divalent orthogonal adamantyl nitrilotriacetate linker ( 4 ) is described. Nonspecific interactions were suppressed by using monovalent adamantyl‐hexa(ethylene glycol) derivative 3 . With the mono‐His 6 ‐tagged maltose binding protein (His 6 ‐MBP), thermodynamic modeling based on surface plasmon resonance (SPR) titration data showed that the MBP molecules in solution were linked, on average, to Ni ⋅4 in 1:1 stoichiometry. On the surface, however, the majority of His 6 ‐MBP was complexed to surface‐immobilized β‐CDs through three Ni ⋅4 complexes. This difference is explained by the high effective β‐CD concentration at the surface and is a new example of supramolecular interfacial expression. In a similar adsorption scheme, SPR proved that the α‐proteasome could be attached to β‐CD SAMs in a specific manner. Patterning through microcontact printing of (His 6 ) 4 ‐DsRed‐fluorescent timer (DsRed‐FT), which is a tetrameric, visible autofluorescent protein, was carried out in the presence of Ni ⋅4 . Fluorescence measurements showed that the (His 6 ) 4 ‐DsRed‐FT is bound strongly through Ni ⋅4 to the molecular printboard.