Multifunctional peptide‐based fluorescent chemosensor for detection of Hg²⁺, Cu²⁺ and S²⁻ ions

Abstract

A novel multifunctional fluorescent peptide sensor based on pentapeptide dansyl-Gly-His-Gly-Gly-Trp-COOH (D-P5) was designed and synthesized efficiently using Fmoc solid-phase peptide synthesis (SPPS). This fluorescent peptide sensor shows selective and sensitive responses to Hg 2+ and Cu 2+ among 17 metal ions and six anions studied in N-2-hydroxyethylpiperazine-N-2-ethane sulfonic acid (HEPES) buffer solution. The peptide probe differentiates Hg 2+ and Cu 2+ ions by a 'turn-on' response to Hg 2+ and a 'turn-off' response to Cu 2+ . Upon addition of Hg 2+ or Cu 2+ ions, the sensor displayed an apparent color change that was visible under an ultraviolet lamp to the naked eye. The limits of detection (LOD) of DP-5 were 25.0 nM for Hg 2+ and 85.0 nM for Cu 2+ ; the detection limits for Cu 2+ were much lower than the drinking water maximum contaminant levels set out by the United States Environmental Protection Agency (USEPA). It is noteworthy that both D-P5-Hg and D-P5-Cu systems were also used to detect S 2− successfully based on the formation of ternary complexes. The LODs of D-P5-Hg and D-P5-Cu systems for S 2− were 217.0 nM and 380.0 nM, respectively. Furthermore, the binding stoichiometry, binding affinity and pH sensitivity of the probe for Hg 2+ and Cu 2+ were investigated. This study gives new possibilities for using a short fluorescent peptide sensor for multifunctional detection, especially for anions. KEYWORDS cupric ion, fluorescent sensor, mercury ion, peptide-based sensor, sulfide ion

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