Chemical immobilization procedure

Chemical immobilization procedures of bioluminescent enzymes such as firefly luciferase and bacterial luciferase-NAD(P)H FMN oxidoreductase to glass beads or rods [174, 175], sepharose particles [176], and cellophane films [177] have produced active immobilized enzymes. Picomole-femtomole amounts of ATP or NAD(P)H could be detected using immobilized firefly luciferase or bacterial luciferase-oxidoreductase, respectively. 

Acoustic wave device as LC detector amount of analyte in detector, 15,16/ chemical immobilization procedure, 13 chromatograms of blank and human immunoglobulin G samples, 13-15 chromatographic system, 11 continuous measurement ability, 15,17 experimental description, 11,13 limitations, 17 sensorgrams, 14/15 surface acoustic wave devices and electronics, 11,12/... 

Enzymes are immobilized by a variety of methods. Two general types of immobilization procedures are used. The first-type procedures are based on weak interactions between the support and the enzyme and are classified as physical methods. The second-type procedures rest upon the formation of covalent bonds between the enzyme and the support and are classified as chemical methods. 

Among various enzyme immobilization protocols, entrapment in polymer membranes is a general one for a variety of transducers. Formation of a membrane from a solution of already synthesized polymer is simpler and reproducible compared to chemical polymerization. The simplicity of this immobilization procedure should provide reproducibility for the resulting biosensors the latter is strongly required for mass production. 

Immobilized antibodies may be used as affinity adsorbents for the antigens that stimulated their production (Figure 6.15). Antibodies, like many other biomolecules, may be immobilized on a suitable support matrix by a variety of chemical coupling procedures. 

Both organic and inorganic polymer materials have been used as solid supports of indicator dyes in the development of optical sensors for (bio)chemical species. It is known that the choice of solid support and immobilization procedure have significant effects on the performance of the optical sensors (optodes) in terms of selectivity, sensitivity, dynamic range, calibration, response time and (photo)stability. Immobilization of dyes is, therefore, an essential step in the fabrication of many optical chemical sensors and biosensors. Typically, the indicator molecules have been immobilized in polymer matrices (films or beads) via adsorption, entrapment, ion exchange or covalent binding procedures. 

The possibility of having membrane systems also as tools for a better design of chemical transformation is today becoming attractive and realistic. Catalytic membranes and membrane reactors are the subject of significant research efforts at both academic and industrial levels. For biological applications, synthetic membranes provide an ideal support to catalyst immobilization due to their biomimic capacity enzymes are retained in the reaction side, do not pollute the products and can be continuously reused. The catalytic action of enzymes is extremely efficient, selective and highly stereospecific if compared with chemical catalysts moreover, immobilization procedures have been proven to enhance the enzyme stability. In addition, membrane bioreactors are particularly attractive in terms of eco-compatibility, because they do not require additives, are able to operate at moderate temperature and pressure, and reduce the formation of by-products. 

They explain three types of immobilization procedures (1) physical adsorption of reagent onto the solid matrix, (2) covalent attachment of a reactive tag through a chemical bond with silanols on the silica surface, and (3) covalent attachment of a reactive tag to an organic polymer coating on the silica surface. 

In most of the traditional immobilization procedures,however, the contributions of recent progress in membrane technology have been very limited. The preparation of enzyme membranes on a large scale for industrial processes, in which selective mass transfer across the artificial membranes is combined with specific chemical reactions,wou1d require low membrane cost and standard preparation procedures. Two immobilization procedures have been recently studied in our laboratory, which might accomplish those requirements. Gelled enzyme membranes,involving labile immobilization at the membrane-solution interface, can result... 

Sometimes even membrane transport and mechanical properties are affected by the harsh chemical treatments required in the immobilization procedure. Figure 7.35 shows how immobilization of urease by diazotization on heterogeneous polysulfone flat membranes reduces the membrane hydraulic permeability by 50%.74 It also shows how the higher permeability membranes are more affected by the immobilization procedure. After the enzyme is immobilized, it is wise to check the integrity of the membrane (e.g., the permeability to the species of interest and the strength).71 74... 

The main methods of immobilization employed to stabilize the life time of photosynthetic material are studied. Various parameters and properties concerning the immobilization procedures are evaluated method, biological material, techniques to measure the photosynthetic activity, storage and operational stabilities. A comparison between two methods of immobilization (chemical and physical) to measure the effect of herbicides which inhibited photosynthesis is discussed. The practical implication of photosystem II is emphasized. 

Biosensors are analytical devices that consist of a biosensing element like photosynthetic materials and a transducer that transfers the chemical signal to an electrical signal. Because the isolated photosynthetic materials have a relatively short active life time, a variety of immobilization procedures have been developed to stabilize the structure and functions of this biological material. Different photosynthetic biosensors used to detect heavy metals are shown in Table 1. 

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