Imprinting, molecular recognition

Prasad, B., and Pandey, 1. (2013). Electrochemically imprinted molecular recognition sites on multiwalled carbon-nanotubes/pencil graphite electrode surface for enantioselective detection of D- and L-asparticacid, ElecUvchinLAc 88, 24-34. 

Prasad, B.B. Madhuri, R. Tiwari, M.P. Sharma, P.S. (2010b). Imprinting molecular recognition sites on multiwalled carbon nanotubes surface for electrochemical detection of insulin in real samples. Electrochimica Acta, 55, 9146-9156. 

B. Sellergren, Noncovalent molecular imprinting antibody-like molecular recognition in polymeric network materials . Trends. Anal. Chem. 16 310-320 (1997). 

Apart from the successful imprinting discussed above, the recognition for many templates is far from that is required for the particular application, even after careful optimization of the other factors affecting the molecular recognition properties. Often, a large excess of MAA in the synthesis step is required for recognition to be observed and then only in solvents of low to medium polarity and hydrogen bond... 

Ye, L Ramstrom, O Mansson, MO Mosbach, K, A New Application of Molecularly Imprinted Materials, Journal of Molecular Recognition 11, 75, 1998. 

Fig. 1. Preparation of configurational biomimetic imprinted networks for molecular recognition of biological substrates. A Solution mixture of template, functional monomer(s) (triangles and circles), crosslinking monomer, solvent, and initiator (I). B The prepolymerization complex is formed via covalent or noncovalent chemistry. C The formation of the network. D Wash step where original template is removed. E Rebinding of template. F In less crosslinked systems, movement of the macromolecular chains will produce areas of differing affinity and specificity (filled molecule is isomer of template).

To prepare artificial enzymatic systems possessing molecular recognition ability for particular molecules, molecular imprinting methods that create template-shaped cavities with the memory of the template molecules in polymer matrices, have been developed [22, 30-35] and established in receptor, chromatographical separations, fine-chemical sensing, etc. in the past decade. The molecular... 

In addition to imprinted acid-base catalysts [49-55], attempts to imprint metal complexes have been reported and constitute the current state of the art [46, 47]. In most cases of metal-complex imprinting, ligands of the complexes are used as template molecules, which aims to create a cavity near the metal site. Molecular imprinting of metal complexes exhibits several notable features (i) attachment of metal complex on robust supports (ii) surrounding of the metal complex by polymer matrix and (iii) production of a shape selective cavity on the metal site. Metal complexes thus imprinted have been appHed to molecular recognition [56, 57], reactive complex stabilization [58, 59], Hgand exchange reaction [60] and catalysis [61-70]. 

Stationary phases with specific molecular recognition properties for D,L-enantiomers of peptides have been tailored using the molecular imprinting technique. A template molecule is added to suitable monomer(s), the system is polymerized, and the chiral template molecule is washed out [128]. 

Biffis A, Graham NB, Siedlaczek G, Stalberg S, Wulff G. The synthesis, characterization and molecular recognition properties of imprinted microgels. Macromol Chem Phys 2001 202 163-171. 

Sellergren B, Andersson L. Molecular recognition in macroporous pol3miers prepared by a substrate-analog imprinting strategy. J Org Chem 1990 55 3381-3383. 

Takeuchi T, Haginaka J. Separation and sensing based on molecular recognition using molecularly imprinted polymers. J Chromatogr B 1999 728 1-20. 

Molecular imprinting is a special polymerization technique making use of molecular recognition [18] consisting in the formation ofa cross-linked polymer around an organic molecule which serves as a template. An imprinted active site capable of binding is created after removal of the template. This process can be applied to create effective chromatographic stationary phases for enantiomers separation. An example of such a sensor is presented in Section 6.3.2.3. 

The performance of the molecularly imprinted monolith in terms of molecular recognition and flow-through properties depends on several factors, especially the density and the porosity of the polymer. In order to obtain a monolith with high selectivity and high permeability, some preparation conditions must be optimised, in particular the composition of the prepolymerisation mixture including the amount of template, the type and amount of functional monomer, crosslinker, porogenic solvent and the initiator, and the polymerisation conditions such as initiation process and polymerisation time. 

The transport properties across an MIP membrane are controlled by both a sieving effect due to the membrane pore structure and a selective absorption effect due to the imprinted cavities [199, 200]. Therefore, different selective transport mechanisms across MIP membranes could be distinguished according to the porous structure of the polymeric material. Meso- and microporous imprinted membranes facilitate template transport through the membrane, in that preferential absorption of the template promotes its diffusion, whereas macroporous membranes act rather as membrane absorbers, in which selective template binding causes a diffusion delay. As a consequence, the separation performance depends not only on the efficiency of molecular recognition but also on the membrane morphology, especially on the barrier pore size and the thickness of the membrane. 

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