Binding, ionic

To develop a continuous process, the immobilisation of aminoacylase of Aspergillus oryzae by a variety of methods was studied, for example ionic binding to DEAE-Sephadex, covalent binding to iodo-acetyl cellulose and entrapment in polyacrylamide gel. Ionic binding to DEAE-Sephadex was chosen because the method of preparation was easy, activity was high and stable, and regeneration was possible. 

The theory and application of this fluorescence method have been discussed in detail by LePecq and others (3,8). The assay requires that there is sufficient ionic strength to minimize ionic binding (e.g., O.IM sodium chloride), that the pH is 4-10, that no heavy metals are present, that the fluorescence is not enhanced on binding to other excipients (e.g., proteins) and that at least portions of the nucleic acids are not complexed. These requirements can usually he met when dealing with recombinant products in some cases the samples must he manipulated to create the appropriate conditions. In the intercalative method of dye binding, proteins rarely interfere with the assay, and procedures have been developed to remove the few interferences they may cause (e.g., the use of heparin or enzymatic digestion of the protein 9). 

On the basis of an IR study of some s-triazines and HA systems, several authors reported that ionic bonding took place between a protonated secondary amino group of the s-triazine and a carboxylate anion on the HA [17,146,147]. Successive studies, mainly conducted by IR spectroscopy, confirmed previous results and also provided evidence for the possible involvement of the acidic phenol-OH of HA in the proton exchange of the s-triazine molecule [17, 146-150]. Differential thermal analysis (DTA) curves measured by Senesi and Testini [146, 147] showed an increased thermal stability of the HA-s-triazine complexes, thus confirming that ionic binding took place between the interacting products. 

The role of the structural properties of pectins was described recently (1) where it was shown that interactions of calcium with pectic substances were directly related to the existence of unbranched and non-esterified galacturonic blocks. Calcium was able to ionically bind two or more chains... 

Ionic binding, in which there is bonding between charged groups or atoms, such as metal ions and the opposite charge on the protein. 

Chemical groups capable of ionic binding of heparin may be introduced onto the polymer surface by radiation grafting of ionogenic monomers, e.g., 2- or 4-vinyl-pyridine, dimethylaminoethyl methacrylate, etc. 64,65). Heparinization proceeds as shown below ... 

The surface properties of this kind of supramolecular systems are really scarce. An interplay between short - range van der Waals forces, ionic binding, chemical bonding, elastic/plastic compression, and long - range electrostatic interactions and capillary forces between macromolecules and surfaces seems to be responsible for the variety of observed interfacial behaviors. 

Membrane bioreactors have been reviewed previously in every detail [3,4,7,8,18], There are two main types of membrane bioreactors (i) the system consists of a traditional stirred-tank reactor combined with a membrane separation unit (Figure 14.1) (ii) the membrane contains the immobilized biocatalysts such as enzymes, micro-organisms and antibodies and thus, acts as a support and a separation unit (Figure 14.2). The biocatalyst can be immobilized in or on the membrane by entrapment, gelification, physical adsorption, ionic binding, covalent binding or crosslinking [3, 7, 18]. Our attention will be primarily focused on the second case where the membrane acts as a support for biocatalyst and as a separation unit, in this study. The momentum and mass-transport process, in principle, are the same in both cases, namely when there is... 

The binding of the biocatalyst to the membrane can be divided into three principal groups ionic binding, crosslinking, and covalent linking. 

A bit of explanation is required here for those readers unfamiliar with the condensation concept, a key notion to describe polyelectrolytes. Consider as here a polyanion. If the charges are brought closer to one another, on the average, below a critical distance their mutual repulsion is such that — in order to continue to obey first principles electrostatics such as the Poisson equation — they screen themselves with an atmosphere of counterions. This atmospheric condensation, which can coexist with ionic binding at the individual sites, boosts the local concentration of counterions in the space surrounding the polyelectrolyte by as much as three orders of magnitude. The nmr measurements analyzed here focus on these water hydration molecules coordinated to condensed sodium counterions, next to the surface of the tactoids (see Fripiat s chapter). 

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