Cross-linking effect covalent attachment

Active derivatives of glucoamylase immobilized on activated carbon have been prepared by adsorption, glutaraldehyde cross-linking, or covalent attachment by reaction with carbodi-imide-activated or diazotized activated carbon. The effects of a number of pretreatments of the carbon matrix on the efficacy of immobilization were investigated. 

Self-Associative Polymer Network. In self-associative polymer networks (often called one component systems), the hydrogen bonding recognition units that are covalently attached to the polymer backbone have an appreciable tendency for self-association, that is, self-dimerize, which leads to interchain cross-linking of the polymers. As a result, the system is inherently cross-linked and does not require any external cross-linking agents for network formation (Fig. 5.11a). Because the cross-linking is based on dimerization phenomena, to achieve effective... 

After cross-linking of the VFA and BVU on the silica particle surface the IEP shifts from pH 3 (bare silica) to pH 5 (PVFA-co-PBVU/silica). The shape of the function = (pH) remains unchanged. It can be assumed that the silanol groups on the silica surface are weakly shielded by the adsorbed sections of the cross-linked polymer because covalent attachment of the polymer does not take place [63, 73]. Strong effects can be seen after conversion of the formamide groups into amino groups. The IEP is shifted into the... 

State. The effect of covalent bonding depends on the location of the bond relative to an active site. If remote from the site, it may have no effect. The chemical nature of the support can affect activity. Cross-linking requires two covalent attachments per enzyme molecule, and is thus likely to distort the shape of the enzyme to the point that catalytic activity is lost. Such distortions are even more likely, but not inevitable, for coagulated or flocculated enz5ones. On the positive side, immobilization tends to stabilize enzymes against deactivation. 

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