Enantioselective uptake of amino acid with overoxidized polypyrrole colloid templated with L-lactate

An overoxidized polypyrrole colloid, which can recognise enantiomers of ami no acids has been prepared by a newly developed molecular imprinting techni que. A polypyrrole colloid, which had been polymerised from a mixture of py rrole (monomer), polyvinylpyrrolidone (steric stabiliser), peroxodisulfate (oxidant) and l-lactate (dopant), was overoxidized to create a dopant-compl ementary cavity. The enantioselectivity of the overoxidized colloid was eva luated by comparing the uptake of l-alanine and l-cysteine with that of the respective d-enantiomers. The l/d uptake ratios for these amino acids were about 2, while phenylalanine showed suppressed uptake for both the enantio mers. The absence of phenylalanine uptake can be explained in terms of the molecular size, which is too large to be accommodated by the cavity created by l-lactate. In contrast, a colloid templated with l-phenyllactate took u p l-phenylalanine with a higher enantioselectivity of about 7. A colloid te mplated with l-lactate was applied to surface chirality analysis through en antioselective adsorption on cysteine-modified gold surfaces. Quartz microb alance experiments and scanning electron microscope observation of the gold surface revealed that the colloidal particle has higher affinity to a surf ace modified with l-cysteine than to one modified with D-cysteine.