Fluorescent peptide dH3w: A sensor for environmental monitoring of mercury (II)

Heavy metals are hazardous environmental contaminants, often highly toxic even at extremely low concentrations. Monitoring their presence in environmental samples is an important but complex task that has attracted the attention of many research groups. We have previously developed a fluorescent peptidyl sensor, dH3w, for monitoring Zn(2+) in living cells. This probe, designed on the base on the internal repeats of the human histidine rich glycoprotein, shows a turn on response to Zn(2+) and a turn off response to Cu(2+). Other heavy metals (Mn(2+), Fe(2+), Ni(2+), Co(2+), Pb(2+) and Cd(2+)) do not interfere with the detection of Zn(2+) and Cu(2+). Here we report that dH3w has an affinity for Hg(2+) considerably higher than that for Zn(2+) or Cu(2+), therefore the strong fluorescence of the Zn(2+)/dH3w complex is quenched when it is exposed to aqueous solutions of Hg(2+), allowing the detection of sub-micromolar levels of Hg(2+). Fluorescence of the Zn(2+)/dH3w complex is also quenched by Cu(2+) whereas other heavy metals (Mn(2+), Fe(2+), Ni(2+), Co(2+), Cd(2+), Pb(2+), Sn(2+) and Cr(3+)) have no effect. The high affinity and selectivity suggest that dH3w and the Zn(2+)/dH3w complex are suited as fluorescent sensor for the detection of Hg(2+) and Cu(2+) in environmental as well as biological samples.