Fluorescent Labelling of Cell Surface Proteins on a Solid Support

A method for decorating bacteria with synthetic receptors while they are attached to a solid support is described. This approach involves two steps. First, E. coli expressing a His‐tagged outer membrane protein C (His‐OmpC) are attached to a monolayer of DNA duplexes appended with a tri‐nitrilotriacetic acid (tri‐NTA) group. The remaining His‐tags, which are not involved in the interaction with the monolayer, can then be modified with additional tri‐NTA‐appended duplexes that bear different functionalities. By labelling the surface‐bound bacteria with an oligodeoxynucleotide (ODN) appended with a fluorescent dye and by turning off its emission using a complementary, quencher‐bearing strand, we demonstrate the versatility of this approach, as well as a means to modify cell membrane proteins on a solid support using simple self‐assembly processes.