Imprinted polymers, molecularly

Molecularly imprinted polymers (MIPs) form when template molecules are surrounded by monomers which then react with cross-linkers to produce a porous polymer around the templating species. Once the template has been removed a porous polymer remains in which the pores are ideal binding sites for a target with the same molecular shape as the template as shown in Fig. 4.28. 

If the template was a transition state analogue for a particular enzyme reaction then the resulting polymer should contain myriads of sites capable to catalysing that reaction. So far this method has been used successfully to prepare catalysts for hydrolysis reactions [57] and Diels-Alder cyclizations [58] but it could equally easily be applied to mimic more traditional enzymes. 

Despite these promising results further progress in molecular imprinting tech- 

UV 210 nm loaded amount 50 nmol. (Reprinted with permission from [205]). 

CDs have a longstanding tradition as versatile host systems in the molecular recognition field, and have seen extensive use in various enantiomer separation techniques [206, 207], including GC, LC, CE and CEC. The widespread applications of CDs for enantiomer separation of chiral drug compounds have been detailed in recent reviews [55, 208]. 

A broad variety of bonded CD-type CSPs have been developed and commercia- 

Typically, the CD molecules in these CSPs are covalently attached to functiona- 

Lund University, Biomedical Center, Department of Experimental Medical Science, 22184 Lund, Sweden 

One of the corner-stones of life is recognition. This phenomenon occurs on a macroscopic level as well as on a microscopic one. For example, the ability to recognize a familiar face is practical in our everyday life and the recognition of a transmitter substance by its receptor is essential for the function of the nervous system. Molecular recognition is the creation of a complex between a host molecule and a guest molecule and often involves non-covalent interactions such as hydrogen bonds, hydrophobic interactions, metal coordination, van der Waals interactions and ionic interactions. 

Molecular recognition elements are useful in a broad range of applications where selective binding is advantageous, for example, chromatographic and batch-wise separation and purification, trace enrichment by solid-phase extraction, 

The Power of Functional Resins in Organic Synthesis. Judit Tulla-Puche and Fernando Albericio Copyright 2008 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 978-3-527-31936-7 

The polymerization runs through the chain-reaction steps, that is, initiation, propagation and termination. After completion of the polymerization, the template is removed from the polymer by extraction (step 3). The resulting polymer is then able to selectively rebind the template molecule (step 4). 

The imprinting molecule complexes one or several functional monomers. The next step is polymerization. As a result, MIPs possess a steric (size and shape) and chemical (special arrangements of complementary functionality) memory for a template. 

Other applications of MIPs have been described by Hung and Hwang for the analysis of sulfonamides and by Turiel et al. for the analysis of fluoroquinolones in soil. 

The system eventually recalls the lock and key model of the enzymes, i.e., it is characterized by a particularly high degree of selectivity. In this regard, it is worth noting that MlPs may offer notable advantages with respect to natural enzymes that are stable only in quite limited experimental conditions, are quite expensive, and are only available for a limited number of possible analytes. 

Some selected applications of ICP for the formation of amperometric sensors based on MIP strategy are reported in Table 2.2. 

Current limitations of molecular imprinting include the frequency of errors in cavity shapes and functionality as well as other defects, due to the irreversibility of the polymerization step. As a consequence, selectivities are lower and loading capacity is diminished. If indeed a reversible step could be incorporated into the process of molecular imprinting, some of the major weaknesses of this technique could be overcome. 

Among the sundry approaches to tackle this issue [108], reversible disulfide bond formation was proven efficient in a seminal publication in 2001 [109]. Building on earlier work by Wulff and Schulze on chirally selective polystyrenes cross- 

In this strategy reminiscent of the reduction-oxidation steps in producing curls in hair by a permanent wave , the calcium ions play the role of the curlers-they reorganize the available carboxylate groups in an optimal geomehy, subsequently immobilized by reoxidation of the mercapto cross-linkers. This reduction-oxidation treatment results in a significant increase in the affinity for calcium ions. In contrast, when the gel was reoxidized in the absence of the calcium template, affinities for calcium dropped. 

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SENSORS BASED ON FREE-STANDING MOLECULARLY IMPRINTED POLYMER MEMBRANES. COMPUTATIONAL MODELLING OF SYNTHETIC MIMICKS OF BIORECEPTORS... 

The development of highly selective chemical sensors for complex matrixes of medical, environmental, and industrial interest has been the object of greate research efforts in the last years. Recently, the use of artificial materials - molecularly imprinted polymers (MIPs) - with high recognition properties has been proposed for designing biomimetic sensors, but only a few sensor applications of MIPs based on electrosynythesized conductive polymers (MIEPs) have been reported [1-3]. 

METAL-LOADED SORBENTS AND MOLECULARLY IMPRINTED POLYMERS IN SPE-LC... 

Recently, molecularly imprinted polymers (MIPs) have gained attention as new, selective sorbents for chromatography and SPE. The cavities in the polymer... 

The sorbents that are most frequently used in environmental analysis are Cig-silica based sorbents, polymeric sorbents (usually styrenedivinilbenzene) and graphitized carbon. In order to increase the selectivity of these sorbents, immunosorbents (35, 36) have been developed and used with good results, while recently, molecularly imprinted polymers have started be to used (35, 36). 

Fig. 5-5. Schematic representation of the preparation procedure of molecular imprinted polymers (MIP).

Molecularly imprinted polymers (MIPs) can be prepared according to a number of approaches that are different in the way the template is linked to the functional monomer and subsequently to the polymeric binding sites (Fig. 6-1). Thus, the template can be linked and subsequently recognized by virtually any combination of cleavable covalent bonds, metal ion co-ordination or noncovalent bonds. The first example of molecular imprinting of organic network polymers introduced by Wulff was based on a covalent attachment strategy i.e. covalent monomer-template, covalent polymer-template [12]. 

Gel materials are utilized in a variety of technological appUcations and are currently investigated for advanced exploitations such as the formulation of intelligent gels and the synthesis of molecularly imprinted polymers. 

Toth E, Hehn L, Merbach AE (2002) Relaxivity of MRI Contrast Agents. 221 61-101 Tovar GEM, Krauter I, Gruber C (2003) Molecularly Imprinted Polymer Nanospheres as Fully Affinity Receptors. 227 125-144... 

Ansell, RJ Mosbach, K, Magnetic Molecularly Imprinted Polymer Beads for Drug Radioligand Binding Assay, Analyst 123, 1611, 1998. 

Piletsky, SA Andersson, HS Nicholls, LA, Combined Hydrophobic and Electrostatic Interaction-Based Recognition in Molecularly Imprinted Polymers, Macromolecules 32, 633, 1999. 

Tan, ZJ Remcho, VT, Molecular Imprint Polymers as Highly Selective Stationary Phases for Open Tubular Liquid Chromatography and Capillary Elechophoresis, Elechophoresis 19, 2055, 1998. 

Advanced techniques like molecularly imprinted polymers (MIPs), infrared/near infrared spectroscopy (FT-IR/NIR), high resolution mass spectrometry, nuclear magnetic resonance (NMR), Raman spectroscopy, and biosensors will increasingly be applied for controlling food quality and safety. 

Zougagh, M., Valcarcel, M., and Rios, A., Automatic selective determination of caffeine in coffee and tea samples by using a supported liquid membrane-modified piezoelectric flow sensor with molecularly imprinted polymer. Trends Anal. Chem., 23, 399, 2004. 

Yano, K. and Karube, I., Molecularly imprinted polymers for biosensor applications. Trends Anal. Chem., 18, 199, 1999. 

The most widely employed techniques for the extraction of water samples for triazine compounds include liquid-liquid extraction (LLE), solid-phase extraction (SPE), and liquid-solid extraction (LSE). Although most reports involving SPE are off-line procedures, there is increasing interest and subsequently increasing numbers of reports regarding on-line SPE, the goal of which is to improve overall productivity and safety. To a lesser extent, solid-phase microextraction (SPME), supercritical fluid extraction (SEE), semi-permeable membrane device (SPMD), and molecularly imprinted polymer (MIP) techniques have been reported. 

Molecular modelling of opioid receptor-ligand complexes, 40 (2002) 107 Molecularly imprinted polymers,... 

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