Probing Biocatalytic Transformations
with Luminescent DNA/Silver Nanoclusters
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Abstract
DNA-stabilized Ag nanoclusters, AgNCs, act as fluorescent
labels for probing enzyme activities and their substrates. The effective
quenching of AgNCs by H<sub>2</sub>O<sub>2</sub> enables the probing
of H<sub>2</sub>O<sub>2</sub>-generating oxidases. This is demonstrated
by following the glucose oxidase-stimulated oxidation of glucose through
the enzyme-catalyzed formation of H<sub>2</sub>O<sub>2</sub>. Similarly,
the effective quenching of the AgNCs by quinones enabled the detection
of tyrosinase through the biocatalyzed oxidation of tyrosine, dopamine,
or tyramine to the respective quinone products. The sensitive probing
of biocatalytic processes by the AgNCs was further implemented to
follow bienzyme catalytic cascades involving alkaline phosphatase/tyrosinase
and acetylcholine esterase/choline oxidase. The characterization of
the alkaline phosphatase/tyrosinase cascade enabled the ultrasensitive
detection of alkaline phosphatase (5 × 10<sup>–5</sup> units/mL) and the detection of <i>o</i>-phospho-l-tyrosine that is an important intracellular promoter and control growth
factor
