Figure 3. a) Representation of the electrochemical upregulation of catalytic activity. Exposure of Au NP 1 to a Cd0-coated electrode results in a weak increase in catalytic activity. Application of an electrochemical trigger to the same solution with a Cu0-coated electrode causes the release of Cu2+. The released Cu2+ displaces Cd2+ from the TACNhead groups. b) Representative example of a displacement experiment (all experiments were performed in triplicate; see the Supporting Information, Figure S9). Trace I : initial exposure of Au NP 1 to a Cdcoated electrode followed by exposure (after 30 min) to a Cu-coated electrode to which an oxidative potential was applied. Trace II : initial exposure of Au NP 1 to a Cu-coated electrode with application of an oxidative potential and subsequent exposure (after 30 min) to a Cdcoated carbon chip. PNP-concentration was measured by UV/Vis spectroscopy at 405 nm. Electrochemical release of Cu2+: ramp of potential from 0.3 to 0.5 V vs. Ag/AgCl for 60 s. c) Averaged rates of HPNPP transphosphorylation after exposure of Au NP 1 to the different carbon electrodes described in (b). Experimental conditions: [TACN]=20 mm, [HPNPP]=1 mm, [HEPES]=10 mm, pH 7.0, 25 8C. Error bars: 1 s.d. calculated from three independent measurements.
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