A “metal ions-induced poisoning behavior of biomolecules” inspired polymeric probe for Cu2+ selective detection on basis of coil to helix conformation transition

Abstract

The interaction between heavy metal ions (e.g. Cu2+, Pb2+, Cr6+) and bioactive biomolecules can severely cause the “poisoning behavior” due to the secondary structure transition. While in a bioinspiration strategy, functional polymers with the ability of selectively responding to metal ions can be used as effective probe candidate for metal ion detection. Herein, a series of functional substituted polyacetylenes with glycine pendants (P-Gly-NH2) are deliberately designed and synthesized as a fresh member of polymeric probe arsenal for selective ions recognition. According to chemical and structural characterization including FT-IR, NMR, GPC, UV–vis and so on, the synthesized P-Gly-NH2 polymers with glycine amide pendants possess random coil conformation on the conjugated main chains. Benefit from remarkable water-soluble ability and secondary structure, P-Gly-NH2 can simulate the biomolecules and apply for heavy metal ions detection in aqueous solution. Because of the complexing interaction with Cu2+, the particular “random coil to helical” conformation transition of P-Gly-NH2 backbone can be observed by UV–vis characterization in ion recognition experiments. Moreover, the relevant results of ions interfering and titration experiments also confirm that this selective detection towards Cu2+ exhibits an outstanding time-efficiency and reliability with the corresponding detection limitation around 0.128 mg/L. As revealed in UV–vis, Raman, FT-IR and XPS spectra characterization, this conformation transition of P-Gly-NH2 is owing to the complexing interaction between Cu2+ and nitrogen atoms in polymer side groups, resulting in an ordered cis-cisoidal helical structures in polymer backbones. In a word, this study not only paves a new way for design and synthesis of water-soluble amino acid-based substituted polyacetylenes, but also implements the functional polymeric probes for selective and sensitive detection of heave ions through a bioinspiration strategy.