Molecular imprinting of proteins emerging as a tool for protein recognition.

This article gives the recent developments in molecular imprinting for proteins. Currently bio-macromolecules such as antibodies and enzymes are mainly employed for protein recognition purposes. However, such bio-macromolecules are sometimes difficult to find and/or produce, therefore, receptor-like synthetic materials such as protein-imprinted polymers have been intensively studied as substitutes for natural receptors. Recent advances in protein imprinting shown here demonstrate the possibility of this technique as a future technology of protein recognition.

Photoresponsive porphyrin-imprinted polymers prepared using a novel functional monomer having diaminopyridine and azobenzene moieties.

A novel photoresponsive functional monomer bearing diaminopyridine and azobenzene moieties was synthesized and applied to the preparation of photo-regulated molecularly imprinted polymers, which can recognize porphyrin derivatives through hydrogen bonding. The binding affinity of the imprinted cavities was regulated by UV irradiation, suggesting that azobenzene groups located inside the binding sites worked as photosensitizers and the trans-cis isomerization could regulate the affinity for the target compounds. Repetitive binding of the target compound to trans-IP and cis-IP was directly monitored by slab optical waveguide spectroscopy and the photo-mediated regulation of binding affinity was successfully confirmed.

Surface plasmon resonance sensor for lysozyme based on molecularly imprinted thin films.

Molecularly imprinted polymers (MIPs) selective for lysozyme were prepared on SPR sensor chips by radical co-polymerization with acrylic acid and N,N'-methylenebisacrylamide. Gold-coated SPR sensor chips were modified with N,N'-bis(acryloyl)cystamine, on which MIP thin films were covalently conjugated. The presence of NaCl during the polymerization and the re-binding tests affected the selectivity and the optimization of NaCl concentration in the pre-polymerization mixture and the re-binding buffer could enhance the selectivity in the target protein sensing. When the lysozyme-imprinted polymer thin films were prepared in the presence of 40 mM NaCl, the selectivity factor (target protein bound/reference protein bound) of MIP in the re-binding buffer containing 20 mM NaCl was 9.8, meanwhile, that of MIP in the re-binding buffer without NaCl was 1.2. A combination of SPR sensing technology with protein-imprinted thin films is a promising tool for the construction of selective protein sensors.

Spectroscopic anatomy of molecular-imprinting of cyclodextrin. Evidence for preferential formation of ordered cyclodextrin assemblies.

The processes of molecular-imprinting of beta-cyclodextrin (beta-CyD) with cholesterol and stigmasterol (cross-linking agent = diisocyanate) have been analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy. These templates enormously promote the formation of dimers and trimers of beta-CyD, which are only inefficiently formed in their absence. These ordered assemblies are the guest-binding sites, in which two or three beta-CyD molecules cooperate to bind large steroids. Ordered assemblies are also formed when 2,6-di-O-methyl-beta-cyclodextrin is used in place of beta-CyD. Direct spectroscopic evidence for molecular-imprinting effect has been obtained. Molecular imprinting of CyDs is potent for tailor-made preparation of synthetic receptors for nanometer-scaled guests.