Similarly to enzymes,f unctionalized gold nanoparticles efficiently catalyze chemical reactions,hence the term nanozymes.H erein, we present our results showing how surface-passivated gold nanoparticles behave as synthetic nanonucleases,a ble to cleave pBR322 plasmid DNAwith the highest efficiency reported so far for catalysts based on asingle metal ion mechanism. Experimental and computational data indicate that we have been successful in creating acatalytic site precisely mimicking that suggested for natural metallonucleases relying on as ingle metal ion for their activity.I tc omprises one Zn(II) ion to which ap hosphate diester of DNAi s coordinated. Importantly,a si nn ucleic acids-processing enzymes,apositively charged arginine playsakey role by assisting with transition state stabilization and by reducing the pK a of the nucleophilic alcohol of as erine.O ur results also show howd esigning ac atalyst for am odel substrate (bis-pnitrophenylphosphate) may provide wrong indications as for its efficiency when it is tested against the real target (plasmid DNA).

A series of 2-nm gold nanoparticles passivated with different thiols all featuring at least one triazacyclonanone-Zn(II) complex and different flanking units (a second Zn(II) complex, a triethyleneoxymethyl derivative or a guanidinium of arginine of a peptide) were prepared and studied for their efficiency in the cleavage of the RNA-model substrate 2-hydroxypropyl-p-nitrophenyl phosphate. The source of catalysis for each of them was elucidated from the kinetic analysis (Michaelis–Menten profiles, pH dependence and kinetic isotope effect). The data indicated that two different mechanisms were operative: One involving two Zn(II) complexes and the other one involving a single Zn(II) complex and a flanking guanidinium cation. The mechanism based on a dinuclear catalytic site appeared more efficient than the one based on the cooperativity between a metal complex and a guanidinium.

The activity of many enzymes is regulated by associative processes. To model this mechanism, we report here that the conformation of an unstructured bimetallic Zn(II) complex can be controlled by its inclusion in the cavity of a γ-cyclodextrin. This results in the formation of a catalytic bimetallic site for the hydrolytic cleavage of the RNA model substrate HPNP, whose reactivity is 30-fold larger with respect to the unstructured complex. Competitive inhibition with 1-adamantanecarboxylate displaces the metal complex from the cyclodextrin decreasing the reactivity.

Similarly to enzymes,f unctionalized gold nanoparticles efficiently catalyze chemical reactions,hence the term nanozymes.H erein, we present our results showing how surface-passivated gold nanoparticles behave as synthetic nanonucleases,a ble to cleave pBR322 plasmid DNAwith the highest efficiency reported so far for catalysts based on asingle metal ion mechanism. Experimental and computational data indicate that we have been successful in creating acatalytic site precisely mimicking that suggested for natural metallonucleases relying on as ingle metal ion for their activity.I tc omprises one Zn(II) ion to which ap hosphate diester of DNAi s coordinated. Importantly,a si nn ucleic acids-processing enzymes,apositively charged arginine playsakey role by assisting with transition state stabilization and by reducing the pK a of the nucleophilic alcohol of as erine.O ur results also show howd esigning ac atalyst for am odel substrate (bis-pnitrophenylphosphate) may provide wrong indications as for its efficiency when it is tested against the real target (plasmid DNA).