Dendrimer Cleaves Cooperatively | Chemical & Engineering News
Volume 85 Issue 22 | p. 31 | Concentrates
Issue Date: May 28, 2007

Dendrimer Cleaves Cooperatively

Department: Science & Technology

The functional units of enzymes often cooperate with each other to carry out catalytic tasks efficiently. Chemists in Italy now show that metal complexes dotting the periphery of a dendrimer also can work cooperatively. Paolo Scrimin of the University of Padova and colleagues functionalized a dendrimer with Zn2+-bound triazacyclononane ligands. They found that it cleaves a phosphate diester model of RNA cooperatively, exhibiting a 270-fold rate acceleration compared with the Zn2+-triazacyclononane complex alone and a 9,900-fold acceleration compared with the uncatalyzed process (J. Am. Chem. Soc. 2007, 129, 6982). The metallodendrimer also shows up to 3.7-fold greater activity compared with gold nanoparticles functionalized with Zn2+ triazacyclononane. The nonlinear dependence of reaction rate on the amount of Zn2+ indicates that two metal ions cooperate to cleave the substrate, the researchers say. The catalytic activity of the functionalized dendrimer is also pH dependent, which the researchers interpret as the two zinc ions stabilizing the transition state and facilitating deprotonation of the substrate.

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