Supports charged

Figure 3.6 Schematic representation of deposition-reduction (DR) method (a) positiveiy charged supports and (b) negativeiy charged supports.

Ionic meso-tetraarylporphyrins can be bound to a range of charged supports including cross-linked polystyrene based anions,78 cations,79 exchange resins, cross-linked and quaternized poly(4-vinylpyridine)80 and the oxides of silica, alumina and magnesia.81 Metalloporphyrins may be attached to supports by coordination of a ligand on the support to the metal centre. Such catalysts mimic... 

A charged support, double layered hydroxide, that can be described by the general formula, Mgi xAlx(OH)2Cl zH20, was used to immobilise [PdCl4]2-/811 While results with this catalyst were only poor in A-methyl pyrrolidinone, good conversion and selectivity was obtained in [(C4)4N]Br with arylchlorides as substrates. By employing microwave irradiation coupling between chlorobenzene and styrene afforded the desired product in 95% yield within 30 minutes. The products were isolated by distillation and the catalytic activity remained essentially stable for at least 5 runs. 

When chymotrypsin is immobilized onto the ethylene-maleic anhydride copolymer, one acidic group is created on the surface for each enzyme molecule immobilized, as shown in Figure 4.6. This and other negatively charged supports attract H+ from the bulk of the solution to the surface of the carrier, so that the local pH at the surface is lower... 

Because the local pH at the surface of the support is lower than the bulk, or measured pH, the apparent pH optimum shifts to higher pH values with this and other negatively charged support materials. Figure 4.4 shows that chymotrypsin immobilized onto an ethylene-maleic anhydride support exhibits a pH optimum of 9.4, almost one full pH unit higher than that observed for the native enzyme. 

H. C. Sacco, Y. lamamoto, J. R. L. Smith, Alkene epoxidation with iodosylbenzene catalysed by polyionic manganese porphyrins electrostatically bound to counter-charged supports, /. Chem. Soc., Perkin Trans. 2 (2001) 181. 

Heparinase immobilized on a negatively charged support probably will result in substrate repulsion, and thus reduced activity due to the strong negative charge of heparin. This result may, in fact, explain the apparent poor activities of some of the immobilized heparinase preparations listed in Table II. 

Charge Supporting skeleton Solubility Flexibility/rigidity Bite angles Chirality... 

This is the first example of cell immobilization achieved. Adsorption is based on electrostatic interactions (van der Waals forces) between the charged supports and the cells immobilized. Generally speaking, hydrophobic surfaces have stronger adhesive ability than hydrophilic ones. One important example of this type of immobilization is the attachment of anchorage-dependent mammalian cells onto microcarriers [13], which are special support matrixes providing a large surface area for cell attachment. 

---