Khalku Karim

Recognition of ephedrine enantiomers by molecularly imprinted polymers designed using a computational approach

A new approach to the computational design of molecularly imprinted polymers (MIP) specific for ephedrine is presented. A virtual library of functional monomers was developed and screened against the template using molecular modelling software. The monomers giving the highest binding score were co-polymerized with a cross-linker in the presence of ephedrine. Control (blank) polymers were prepared under the same conditions but in the absence of the template. A good correlation was found between the modelling results and performance of the materials in an HPLC study. A MIP based on one of the selected monomers—hydroxyethyl methacrylate—gave a separation of ephedrine enantiomers with a separation factor α of 1.42–2.09 (depending on temperature). This figure is larger than the α values generally obtained with commercially available chiral phases. It is anticipated that the computational approach will be of use for the rational design of MIPs and the prediction of polymer affinity and specificity.

Substitution of Antibodies and Receptors with Molecularly Imprinted Polymers in Enzyme-Linked and Fluorescent Assays

A new technique for coating microtitre plates with molecularly imprinted polymers (MIP), specific for low-molecular weight analytes (epinephrine, atrazine) and proteins is presented. Oxidative polymerization was performed in the presence of template; monomers: 3-aminophenylboronic acid (APBA), 3-thiopheneboronic acid (TBA) and aniline were polymerized in water and the polymers were grafted onto the polystyrene surface of the microplates. It was found that this process results in the creation of synthetic materials with antibody-like binding properties. It was shown that the MIP-coated microplates are particularly useful for assay development. The high stability of the polymers and good reproducibility of the measurements make MIP coating an attractive alternative to conventional antibodies or receptors used in enzyme linked immunosorbent assay (ELISA).

A new reactive polymer suitable for covalent immobilisation and monitoring of primary amines

A new polymer capable of reacting with primary amines was synthesised from allyl mercaptan, o-phthalic dialdehyde and ethylene glycol dimethacrylate by radical polymerisation. Reactive hemithioacetal formed by allyl mercaptan and dialdehyde can bind primary amino groups without additional pre-activation forming the fluorescent isoindole complex. It gives a great opportunity to monitor binding and perform loading of the amino compounds onto the reactive surface. The reactive polymer is found to be an effective matrix for immobilisation of the proteins and other amino-containing compounds in affinity chromatography and could be used for their detection in solution

Mimicking the Plastoquinone-Binding Pocket of Photosystem II Using Molecularly Imprinted Polymers

The photosystem II (PSII) is a complex system consisting of at least 10 proteins. The electron-flow events in PSII are mediated via prosthetic groups (plastoquinones QA and QB) bound to two proteins called D1 and D2. A large group of photosynthesis-inhibiting herbicides consisting of arylureas, triazines, triazinones and phenylic herbicides has an ability to replace the plastoquinone QB from its binding pocket located in the D1 protein, interrupting the electron flow between the photosystems and causing the plant’s death. The plastoquinone-binding pocket continues to be a subject of intense research by specialists working on the design and testing of new herbicides, as well as scientists and engineers developing new sensors for herbicide detection. The goal of this review is to analyze the structure of the herbicide-binding pocket of the D 1 protein in comparison to known natural and synthetic receptors of herbicides with the aim of developing efficient synthetic mimics useful in the generation of new stable environmental sensor devices.

PREPARATION AND USE OF MEMBRANES WITH POTENTIAL-CONTROLLED FUNCTIONS

A new type of membrane with potential-controllable functions was prepared by grafting polyaniline to the surface of track-etch Nucleopore membrane with a vacuum deposited gold layer (PANI-membranes). Because of the cylindrical shape of these pores, a nanocylinder of the desired conducting material is obtained in each pore. A potential applied to PANI-membranes governs the properties of the conducting layer, such as charge and its distribution, conformation, and density and, hence, controls the diffusion rate of substances through these membranes. The variation in diffusion rates of different substances with different potentials applied to PANI-membranes provides the basis for the application of these membranes in separation processes and sensors.