Covalent immobilisation

Another way for covalent immobilisation is to synthesise indicator chemistry with polymerizable entities such as methacrylate groups (Figure 4). These groups can then be copolymerized with monomers such as hydrophobic methyl methacrylate or hydrophilic acryl amide to give sensor copolymers. In order to obtain self-plasticized materials, methacrylate monomers with long alkyl chains (hexyl or dodecyl methacrylate) can be used. Thus, sensor copolymers are obtained which have a Tg below room temperature. Similarly, ionophores and ionic additives (quaternary ammonium ions and borates) can be derivatised to give methacrylate derivatives. 

Lofas S., Johnsson B., A novel hydrogel matrix on gold surfaces in surface plasmon resonance sensor for fast and efficient covalent immobilisation of ligands, J.Chem.Soc., Chem.Commun. 1990 21 1526-1528. 

The immobilisation by electrostatic interactions of longer, 26 bp ssDNA strands on hard, poly(lysine)-coated glass resulted in aggregates of 63 nm (Fig. 26) [163]. Finally, when DNA molecules of the same length (26 bp) were covalently immobilised on the surface of plasma-induced, NHS-... 

Compagnone et al. [5] Glycerol Alcoholic fermentation Glycerokinase (GK) and glycerol-3-phosphate oxidase (GPO)/ covalently immobilised (Bioreactor of GK and bioelectrode of GPO) Pt-based hydrogen peroxide probe/+650mV vs. Ag/AgCl -... 

A. Ruffien, M. Dequaire and P. Brossier, Covalent immobilisation of oligonucleotides on p-aminophenyl-modified carbon screen-printed electrodes for viral DNA sensing, Chem. Commun., 7 (2003) 912-913. 

Mielgo I, Palma C, Guisan JM et al (2003) Covalent immobilisation of manganese peroxidases (MnP) from Phanerochaete chrysosporium and Bjerkandera sp. BOS55. Enzyme Microb Technol 32 769-775... 

The purpose of this study was to design biosensors on the basis of covalently immobilised lipoxygenase and oxygen electrodes. 

Chevrier, D., Popoff, M.Y., Dion, M.P., Hermant, D., and Guesdon, J. L. (1995) Rapid detection of Salmonella subspecies I by PCR combined with non radioactive hybridisation using covalently immobilised oligonucleotide on a microplate. FEMS Immunology and Medical Microbiology, 10, 245 251. 

These types of immobilisations combine the stabihty and reproducibility of covalent immobilisation with the orientational advantages of protein A/G coupling. Together they offer many advantages over each method individually, but they have longer and more complex procedures, and in some cases this may not be justified by the increase in sensitivity. Realistically the production of a SAM, activation and immobilisation of protein A/G followed by antibody immobilisation is not too difficult, and in a laboratory-based test the potential increase in sensitivity makes the procedure worthwhile. But for commercialisation and mass production the increase in sensitivity must be significant before the increase in preparation time and cost can be justified. 

Basso A, De Martin L, Ebert C et al. (2003) Organically modified xerogels as novel tailor-made supports for covalent immobilisation of enzymes (penicillin G acylase). Tetrahed Lett 44 5889-... 

Caputo, G. Della, C. L. General method for the covalent immobilisation of indicators in, or onto a support useful for the fabrication of optical sensors. Eur. Pat. Appl. EP 1213583, 2002 Chem. Abstr. 2002,137, 14966. 

A non-covalent immobilisation of chiral trans-N,N-dipTopyl diaminocyclo-hexane was also investigated by the same authors on the basis of acid-base interactions. This immobilisation strategy employed solid acids, such as polystyrene (PS)/sulfonic acids. The involvement of these heterogeneous catalysts in the aldolisation of cyclohexanone with benzaldehydes allowed the aldol products to be synthesised in excellent yields and enantioselectivities of up to 99% ee eombined with moderate to high nnti-diastereoselectivities of up to 92% de, as shown in Seheme 2.33. Furthermore, these polymeric sulfonic acids could be easily reeovered by filtration and reused for six eyeles with a similar stereoseleetivity but a slightly decreased activity. 

Currently we are also investigating the effect of covalent immobilisation of different ion receptors for heavy metal ions, which can be used in a micro flow system and can be implemented in a total analysis system circuit. 

First, a reactive comonomer unit can be introduced for a direct covalent immobilisation. When the material surface to be coated contains hydroxyl groups (e.g., glass, silicon, titanium alloys), the silyl-hydroxyl reaction can be used. Following this route, Yang et al. (2010) combine A-isopropyl acrylamide (NiPAAm) with a 3(trimethoxysi-lyOpropyl methacrylate unit to provide a stable thermo-responsive cell culture surface on glass carriers. On an amine-modified surface, a randomly distributed copolymer of... 

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