Immobilization salt concentration

A dual-transducer approach based on sol-gel optical sensors was recently reported to measure acid and salt concentrations in concentrated aqueous and HC1 solutions57. The acid sensors containing bromocresol purple, neutral red, and bromocresol green indicators were obtained by the immobilization of indicators in sol-gel derived films. The salt-HCl solution was flowed through the sensor cell58. 

That ionic immobilization is strongly dependent on the pH value and salt concentrations during immobilization and of the reaction mixture in which the enzyme is used cannot be overemphasized. If these parameters are not taken into... 

For immobilization of purified recombinant proteins, approximately 2 nmol of the protein in solution was applied to a 4-mm diameter disk of PVDF membrane by centrifugation using a ProSpin Sample Preparation Cartridge. The proteins were dissolved in the following water, 0.1% TEA in water, 20% acetonitrile in water, NaCl, Triton, PBS, or urea (total buffer/salt concentration < 100 mM). Generally, the concentration of the protein in solution was 0.5 to 1 pg/pL. 

Arylsulfohydrolase A forms an enzymatically active insoluble complex with a plant lectin, concanavalin A (Con A), at a high salt concentration, where electrostatic interactions are minimal (Bishayee et al., 1973 Bishayee and Bachhawat, 1974 Farooqui and Srivastava, 1981). This insoluble complex can be isolated by centrifugation. Con A-immobilized enzyme has greater thermostability (Ahmad et al., 1973 Farooqui and Srivastava, 1981) and displays a broad pH optimum between pH 3.5 and 4.5. Immobilization on Con A also induces changes in the affinity of substrate with arylsulfohydrolase A. The kinetic properties of free and immobilized arylsulfohydrolase A are shown in Table 3. 

In general, an enzyme will retain its proper three-dimensional conformation when it is in an environment most like its native environment, that is, aqueous, usually close to neutral pH, and containing a moderate salt concentration. Of course, the optimum environment will vary for each enzyme. Therefore, an immobilization matrix should reflect these preferences. Although most pure polymers would be ill suited to be congenial enzyme environments, polymer membranes that are created by cross-linking in an aqueous solution, or by aqueous electrochemical polymerization, contain sufficient water to be hospitable environments. 

This system behaves like a nonpolarizable interface. The salt concentration ratio will not be affected by potential applied from an extraneous source. The equilibrium potential depends only on the standard potentials of transfer of the ions in particular, it does not depend on the initial concentrations (ca and cp) nor is it a function of the phase volumes. Therefore, if only one salt is present in a LL system, the system is not amenable to potentiometric studies. It is thus essential that a supporting electrolyte be present to observe a potentiometric response of a third ion. The need to have a supporting electrolyte is similar to the need of immobilized ions in an ion exchanger membrane of an ion-selective electrode it also explains why it is essential that a supporting electrolyte or physiological concentration of salts must be present in measurements that employ fluorescent dyes. 

The immobilization of a-amylase, 3-D-galactosidase, and D-glucose isomerase by adsorption onto gallotannin coupled to aminohexyl-cellulose has been described.Conditions of the adsorption process studied included time of contact, protein concentration, salt concentration, pH, temperature, and buffer used. 

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