Biomimetic traps for Dioxins: a mixed Computational and Experimental Approach

Dioxins are highly toxic substances, and well known environmental pollutants and carcinogens. It is of fundamental importance to build a selective sensor for this class of compounds. Our approach relies on the design and development of artificial peptides as a mimic of the Aryl Hydrocarbon receptor binding site (Ah; dioxin receptor) in the living cells. A series of pentapeptides have been designed and their affinity toward dioxin was tested by a computational approach (LEAPFROG (TM) algorithm). Two peptides A and B (A: [N]Asn-Phe-Gln-Gly-Ile[C]; B: [N]Asn-Phe-Gln-Gly-Phe[C]), have been chosen in order to evaluate their potential applicability in solid-gas analysis by using a QCM (Quartz Crystal Microbalance) sensor arrays. The peptide sequences were functionalised by two terminal cysteine residues in order to achieve a covalent interaction with the QCM gold surface. The peptide immobilisation was accomplished by dipping of the quartz surfaces in mM solution of A and B in i) water and ii) EtOH/water (1:1 v/v). A quantitative evaluation of mass deposition can be obtained from the differences on the quartz frequency resonance. A strong influence of the solvent of the dioxin stock solution (e.g. hexane, toluene) was tested. Both of the QCM sensors (A and B) gave a good linearity against different sample concentrations. In particular, their desorption coefficients (at 20 ppb concentration) were nicely dependent on the free energy of interaction calculated by computational modelling.