In several ways, the triangular nanoswitch 1  mimics the mode of operation of the SARS-CoV 3C-like protease (3CLpro) that plays a vital role in transforming two polyproteins of the SARS virus into active subunits required for genome replication and transcription. Like the natural enzyme, the monomeric nanoswitch 1 is inactive because its catalytic machinery is frozen in the collapsed state, while it is only catalytically active as a homodimer.Herein, the design and synthesis of the new triangular nanoswitch 1  and its mode of operation is demonstrated. It can be toggled between open and closed form upon addition and removal of Cu+. Besides, the closed switch [Cu(1  )]+ can be operated between a catalytically active dimeric and an inactive monomeric form by alternate addition of Fe2+ and 4-N,N-dimethylaminoterpyridine. In the active form, the nanoswitch [Fe(Cu(1  ))2]4+ exposes the catalytically relevant [Cu(phen)]+ sites that are demonstrated to catalyse the cyclopropanation of Z-cyclooctene by ethyl diazoacetate.Moreover, the system serves as a show case for how a metal ion signal (Fe2+ input) can turn ON a process that is catalysed by a completely different metal ion. In principle, the same mode of operation should be applicable to hide any catalytically active metal ion in the heteroleptic complex [M(1  )]n+ and expose its active site(s) after generation of the dimeric complex.

Monomer-dimer nanoswitch that mimics the working principle of the SARS-CoV 3CLpro enzyme controls copper-catalysed cyclopropanation

248th National Meeting (2014)

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