PubMed · 3353034
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T J Gibson. 1988-03-23. Chelation therapy.. https://pubmed.ncbi.nlm.nih.gov/3353034/
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Thin coatings of molecularly imprinted, metal-complexing polymers have been grafted to activated silica beads suitable for high-performance liquid chromatography (HPLC). Propylmethacrylate-activated silica particles were coated by copolymerization with a metal-chelating monomer, Cu(2+)-[N-(4-vinylbenzyl)-imino]diacetic acid, a metal-coordinating (imidazole) template, and ethylene glycol dimethacrylate. After extraction to remove the template and re-loading with metal, the composite materials re-bind the templates with which they were prepared and exhibit selectivities comparable to bulk-polymerized imprinted materials. The strong Cu(2+)-imidazole interaction, desirable for creating a high-fidelity imprint, leads to excessive retention in elution chromatography. By replacing the copper in the imprinted metal-complexing polymers with weaker-binding Zn2+, these novel ligand-exchange supports can effect partial to complete chromatographic separation of their bis-imidazole templates from other, highly similar imidazole-containing substrates. This "bait-and-switch" approach can significantly enhance the performance of molecularly imprinted materials. Scatchard plots of equilibrium binding data show a significant degree of heterogeneity in the imprinted binding sites of material prepared with a bis-imidazole template, but not with a mono-imidazole template. The best chromatographic separations are observed with small sample sizes, where the substrates occupy the strongest (highest-fidelity) sites.