New biomimetics molecules for biosensing applications

In the last years increasing attention has been paid to the development of biosensors to enhance on-site testing for minimally invasive medical analysis, food quality and safety, environmental protection, homeland security. The realisation and commercialisation of suitably robust biosensors has been delayed by several efforts especially associated with the biological component, regarding stability, poor performance, immobilisation, compatibility in integrated systems (1). The exploration of possible solutions in this issue has led to the design of biomimetic molecules which show a valid alternative to the natural molecules. Among these, peptido-mimetics are compounds which mimic the biological activity of proteins while offering the advantages of increased bioavailability, stability, efficiency and selectivity against the natural biological target of the parent molecules. A peptido-mimetic is a small protein chain designed to mimic a peptide and arises from modification of an existing protein in order to alter the molecule properties. For these reasons biomimetics are considered the new generation of biologically active tools. In this work, an artificial peptide of 70 amino acids was designed on the basis of the D1 protein QB binding site of the photosystem II from the green photosynthetic algae Chlamydomonas reinhardtii (2,3). The peptide goes from the amino acid position 211 to the amino acid position 280 of the D1 protein and cover the QB binding niche, also binding site of several herbicide pollutants. It is composed of two ?-helices, useful for the immobilization on supports, and a loop that represents the binding site. The implemented synthetic molecule was designed as biomimetic material for the development of an optical multi-array biosensor, possibly able to recognise toxic chemicals which affect environmental, agrifood and human health, and fluorescence spectroscopy and circular dichroism studies were performed in order to characterise the conformational structure of the peptide. The molecule was labelled with commercial fluorophores and immobilised on liposomes; optical tests were conducted to identify the binding mechanism towards several herbicides and compared with the natural ability of Chlamydomonas reinhardtii to bind herbicides and fluoresces. Future perspective implies the design of an array of several genetic variants using a computational approach and of relative peptido-mimetic molecules for the screening of a wide range of pollutants.