Abstract
Based on a β-hairpin structure, two new water-soluble peptidyl chemosensors, HP7-H2H11 and HP7-H1H12, were designed and synthesized. In the peptides we implanted histidine as a metal-binding unit and tryptophan as a reporting unit. These two peptides are sensitive and selective to the detection of Cu 2+ and Hg 2+ with a detection limit in the range of 0.6 to 1 μM. The dissociation constants (K d ) of Cu 2+ binding are smaller than those of Hg 2+ binding in HP7-H2H11 and HP7-H1H12, indicating that the peptides have a higher affinity to Cu 2+ than Hg 2+ . pH-dependent fluorescence measurements could be used to discriminate between Cu 2+ and Hg 2+ in solution due to the fact that these two metal ions had significantly different quenching effects on the fluorescence of HP7-H2H11 and HP7-H1H12 under alkaline conditions. Circular dichroism (CD) measurements further showed that Cu 2+ and Hg 2+ have distinct effects on the secondary structure of the peptides, providing a complimentary means to differentiate Cu 2+ from Hg 2+ . © 2013 The Royal Society of Chemistry.