Development of molecularly imprinted polymers for the binding of nitrofurantoin

Novel molecularly imprinted polymers (MIPs) for the recognition of nitrofurantoin (NFT) were prepared by photoinitiated polymerisation in polar solvent using 2,6-bis(methacrylamido) pyridine (BMP) as the functional monomer and carboxyphenyl aminohydantoin (CPAH) as the analogue of the template. The binding constants of the complex between BMP and nitrofurantoin or CPAH in DMSO were determined with 1H NMR titration to be 630 ± 104 and 830 ± 146 M⁻¹, respectively. To study the influence of the functional monomer, two polymer compositions were prepared containing the template, the functional monomer and the crosslinker in the molar ratio 1:1:12 for MIP1 and 1:4:20 for MIP2, respectively. The imprinting factor at saturation concentration of nitrofurantoin, which is the ratio of the amount bound to the MIP and the non-imprinted control polymer (NIP), was determined to be 2.47 for MIP1 and 2.49 for MIP2. The cross reactivity of the imprinted polymers seems to be determined by the ability to form hydrogen bonds to the functional monomer while the shape of the molecule has no real influence.     

Femtochemistry in enzyme catalysis: DNA photolyase

Photolyase uses light energy to split UV-induced cyclobutane pyrimidine dimers in damaged DNA. This photoenzyme encompasses a series of elementary dynamical processes during repair function from early photoinitiation by a photoantenna molecule to enhance repair efficiency, to in vitro photoreduction through aromatic residues to reconvert the cofactor to the active form, and to final photorepair to fix damaged DNA. The corresponding series of dynamics include resonance energy transfer, intraprotein electron transfer, and intermolecular electron transfer, bond breaking-making rearrangements and back electron return, respectively. We review here our recent direct studies of these dynamical processes in real time, which showed that all these elementary reactions in the enzyme occur within subnanosecond timescale. Active-site solvation was observed to play a critical role in the continuous modulation of catalytic reactions. As a model system for enzyme catalysis, we isolated the enzyme–substrate complex in the transition-state region and mapped out the entire evolution of unmasked catalytic reactions of DNA repair. These observed synergistic motions in the active site reveal a perfect correlation of structural integrity and dynamical locality to ensure maximum repair efficiency on the ultrafast time scale.