Jun-ichiro Izumi

Molecularly imprinted polymeric membranes for optical resolution

Abstract d -Tryptophan permeated faster than l -tryptophan through the molecularly imprinted polymeric membranes bearing tetrapeptide derivative as a molecular recognition site.

Alternative molecularly imprinted membranes from a derivative of natural polymer, cellulose acetate

Molecularly imprinted polymeric membranes were prepared from cellulose acetate (CA), of which acetyl content was 40%, by applying the alternative molecular imprinting technique. The Z-d-Glu imprinted polymeric membranes thus obtained recognized d-Glu in preference to l-Glu from racemic Glu mixtures and vice versa. The affinity constants between Glu and the chiral recognition site for two kinds of membranes were determined to be 3.1 × 103 mol−1 dm3 from the adsorption isotherm of d-Glu or L-Glu in the molecularly imprinted CA membranes. Enantioselective electrodialysis was attained with the present membranes reflecting their adsorption selectivity. d-Glu was preferentially permeated through the Z-d-Glu imprinted CA membrane, whereas L-Glu was permeated through the Z-L-Glu imprinted CA membrane. The present study suggests that the molecularly imprinted CA membranes are applicable to the optical resolution of racemic amino acids.

Molecularly imprinted polymeric membranes having EFF derivatives as a chiral recognition site

Molecularly imprinted polymeric membranes with the tripeptide residue H-Glu(OBzl)-Phe-Phe-CH 2 - (EFF) were prepared during the membrane preparation (casting) process in the presence of a print molecule. The Ac-L-Trp imprinted polymeric membranes thus obtained showed adsorption selectivity toward Ac-L-Trp. From adsorption isotherms of Ac-Trp isomers it is seen that the chiral recognition site formed in the presence of the print molecule in the membrane preparation process exclusively recognizes the isomer Ac-L-Trp which was the print molecule, while the opposite isomer, Ac-D-Trp, is rigorously rejected. The affinity constant between Ac-L-Trp and the chiral recognition site was determined to be 9.6 x 10 3 mol -1 . dm 3 . Enantioselective permeation can be attained by applying electrodialysis as a driving force. An optimum separation factor toward the L-isomer of 6.8, which corresponds to the adsorption selectivity, can be reached.

Novel membrane materials having EEE derivatives as a chiral recognition site

Abstract Molecularly imprinted polymeric membranes with tripeptide residue H–Glu(OBzl)–Glu(OBzl)–Glu(OBzl)–CH 2 – (EEE) were prepared during the membrane preparation process in the presence of a print molecule. The Boc– l -Trp imprinted polymeric membranes thus obtained showed adsorption selectivity toward the print molecule analogue, Ac– l -Trp. From the adsorption isotherms of Ac–Trp’s, the chiral recognition site, which was formed by the print molecule in the membrane preparation process, exclusively recognizes Ac– l -Trp, and the opposite isomer, Ac– d -Trp, is rejected. Enantioselective electrodialysis was attained and the separation factor toward l -isomer reached 5.0, reflecting adsorption selectivity. The membrane performance, such as the amount of enantiomer recognized and flux value of enantioselective electrodialysis, are greatly dependent on the concentration of tripeptide residues in the membrane.

Recognition and selective transport of nucleic acid components through molecularly imprinted polymeric membranes

To induce “molecular memory” in a membrane substrate at the same time that the membrane was prepared from its polymer solution, an alternative molecular imprinting technique was applied. Upon membrane formation, a “molecular memory” of the imprint molecule is retained by the formed membrane that recognizes or favors interaction with print molecule analogues. In the present study, polystyrene resin bearing a tetrapeptide derivative, a derivative of natural polymer, and an entirely non-chiral synthetic polymer were adopted as candidate materials to form molecular recognition sites. 9-Ethyladenine was adopted as a print molecule. These molecularly imprinted polymeric membranes recognized and adsorbed adenosine (As), which is an analogue of the print molecule, in preference to guanosine (Gs) from As/Gs mixtures. However Gs was permeated in preference to As contrary to adsorption selectivity, possibly because of the relatively high affinity between As and the membrane.

Novel polymeric membranes having chiral recognition sites converted from tripeptide derivatives.

Six kinds of tripeptide derivative consisting of L-glutamic acid gamma-benzyl ester [Glu(OBzl)] (E) and L-phenylalanine (Phe) (F), i.e. EEF, EFE, FEE, FEF, FFE and FFF, were converted into chiral recognition sites by adopting Boc-L-Trp as a print molecule. The formed chiral recognition sites discriminated between Ac-L-Trp and the corresponding D-isomer, and the L-isomer was incorporated into the membrane in preference to the D-isomer. The affinity constants between the recognition site formed in each membrane and Ac-L-Trp were determined to be 9.6 x 10(3) to 8.4 x 10(3) mol-1 dm3. The affinity constant depends on both the tripeptide sequence and the amino acid residue content. Tripeptide derivatives containing more glutamic acid derivative residues or glutamic acid derivative as an amino-terminal residue show higher affinity constants.