A new water-soluble fluorescent Cu(II) chemosensor based on tetrapeptide histidyl-glycyl-glycyl-glycine (HGGG)

A new water-soluble fluorescent chemosensor Fluor-HGGG was synthesized by linking a tetrapeptide histidyl-glycyl-glycyl-glycine (HGGG) with fluorescein via standard solid-phase 9-fluorenylmethoxycarbonyl (Fmoc) chemistry. Significant fluorescence quenching was observed with Fluor-HGGG in the presence of Cu2+. Other metal ions including Ag+, Ca2+, Cd2+, Co2+, Fe2+, Fe3+, Hg2+, Mn2+, Ni2+ and Zn2+ produced only minor changes in fluorescence values for the system. The dissociation constant (KD) of Cu2+ binding in Fluor-HGGG was found to be 37 μM. The maximum fluorescence quenching caused by Cu2+ binding in Fluor-HGGG was observed over the pH range 7–7.5.