Enantioselective Molecularly Imprinted Polymer for Tyrosine, Tryptophan, and Phenylalanine, and the Possibility of the Crop-Circle-Like Imprinting.

ABSTRACT

Molecularly imprinted polymer (L-MIP) for L-tyrosine (L-Tyr) is prepared by the complexation between quaternized poly(4-vinylpyridine/divinylbenzene) (QVP) and poly(acrylamide-co-acrylic acid) (PAmA) in alkaline solution. The L-MIP shows higher enantioselectivity for L-isomers of tyrosine, together with tryptophan (Trp) and phenylalanine (Phe) compared to the D-isomers of them. The sorption isotherms of the three D-enantiomers are converged to one isotherm. It can reflect that the sorption of D-enantiomers can be relied mainly on the common segment, -CH2 -CH(NH2 )-COOH, neglecting any effect of bulkier aromatic groups. The imprinted common segment can be opened on the surface of MIP from the D-enantiomers. For the L-enantiomers, the sorption discrepancies are depended on the size of the aromatic group implying that the phenolic moiety of L-Tyr can be also opened. Thus, the imprinted sites are proposed to be opened on the surface of L-MIP similar to the crop-circle-like. The enantioselectivity factors, αef  = QL /QD , for Tyr, Trp, and Phe are 1.52, 1.30, and 1.52 for L- to D-isomers, respectively. And the uptake differences between D- and L-enantiomers of Tyr, Trp, and Phe are 31.8, 20.7, and 29 mg per 1 g MIP, respectively.