Highly selective and water-soluble peptidyl chemosensors for copper(ii) and mercury(ii) ions based on a β-hairpin structure

• Published in: Analytical methods Vol. 5; no. 7; pp. 1702 - 1707
• Main Authors: Lu, Ming-Chou, Chiu, Ling-Ying, Chiu, Li-Yang, Lin, Chih-Ying, Horng, Jia-Cherng
• Format: Journal Article
• Language: English
• Published: 01.01.2013
• Subjects: Binding; circular dichroism spectroscopy; Constants; copper; detection limit; Dichroism; dissociation; Fluorescence; Histidine; Mathematical analysis; mercury; metal ions; Peptides; Quenching; tryptophan; water solubility
• ISSN: 1759-9660; 1759-9679; 1759-9679
• DOI: 10.1039/c3ay26524b

Based on a beta -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 super(2+) and Hg super(2+) with a detection limit in the range of 0.6 to 1 mu M. The dissociation constants (K sub(d)) of Cu super(2+) binding are smaller than those of Hg super(2+) binding in HP7-H2H11 and HP7-H1H12, indicating that the peptides have a higher affinity to Cu super(2+) than Hg super(2+). pH-dependent fluorescence measurements could be used to discriminate between Cu super(2+) and Hg super(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 super(2+) and Hg super(2+) have distinct effects on the secondary structure of the peptides, providing a complimentary means to differentiate Cu super(2+) from Hg super(2+).