Enzymatic methods conventional

Fig. 23. Relationship between glucose concentrations of human blood plasma samples measured by a glucose-sensitive FET sensor and by a conventional enzymatic method (F = 1.007X 14, r = 0.988, n = 101). (Re-...

Enzymatic Methods The use of enzymes to produce fatty acids and fatty acid-derived products has been a focus in both academic and industrial circles. Lipases may catalyze esterification, hydrolysis, or exchange of fatty acids in esters (115). These processes can be selected by choosing appropriate substrates and reaction conditions. Lipase-catalyzed processes have attracted attention because of the mild reaction conditions under which they occur and the selectivity displayed by these catalysts. In both respects, they differ from typical chemical reactions. As enzymatic reactions occur under mild temperature and pH conditions and at ambient pressure, they generally require less energy and are conducted in equipment of lower capital cost than many other chemical processes. Another advantage of enzymatic process is related to the selectivity of many lipases, which allows obtaining products that are difficult to produce by more conventional chemical reactions. 

Enzymatic methods generally offer greater specificity over conventional non-enzymatic colorimetric methods for the measurement of uric acid. Even so, methods that depend upon the use of oxidizing agents—such as phosphotungstic acid to oxidize uric acid to allantoin and carbon dioxide, and the resulting reduction of... 

Several enzymatic methods in conjunction with conventional organic methods provide new synthetic routes to fluorinated sugars. These new methods allow preparative synthesis of sugars containing the fluorine probe for use in the NMR study of receptor-substrate interactions of enzymes, of cell-surface glycoproteins, and of other systems related to biochemical recognition... 

Variables and Measurement Methods. Serum lipids were measured by the conventional enzymatic method, and apolipo-proteins (apo) were measured by immunonephelometry. The serum hpoprotein lipase (LPL) mass was measured by the method of Kobayashi et al. (13) using anti-LPL antibody. Quantification of RLP was carried out by the method of Naka-jima et al. (9,10). The RLP fraction was directly isolated from each serum sample using an immunoaffinity-mixed gel conjugated with anti-apo B-lOO and anti-apo Al monoclonal antibodies as shown in Figure 2. Cholesterol and triacylglycerol... 

The cellular reduction/oxidation (redox) state has been found to be involved in the regulation of cell proliferation, differentiation, and apoptosis. Generally, the cellular redox state is a balance between the relative quantities of the intracellular oxidative substances (reactive oxygen species) and reductive substances (reduced glutathione). Conventionally, intracellular ROS and GSH can only be determined by flow cytometry, HPLC, or enzymatic methods. Qin et al. [8] have described a microfluidic device method with LIF detection for simultaneous, rapid determination of intracellular ROS and GSH in apoptotic... 

There are a number of ways in which enzymatic studies contribute to the understanding of the proteome. Enzymes are commonly used in proteomics to investigate analytes that are difficult to measure by conventional means. Quantitation of small molecules with enzymatic methods provides insight into the concentration and activity of the proteins associated with those molecules. A great variety of these enzymatic assays have been carried out in microfluidic devices. Another function of enzymatic assays is in kinetics measuiements of properties of enzymes such as the MichaeUs-Menten constant (the concentration of substrate when the reaction rate is half the maximum rate) and the turnover number (the number of moles of substrate that are converted to product per catalytic site per unit time) are vital to understanding the mechanics of the proteome, and are used to characterize of the effects of known drugs and discover new ones. 

Some methods to measure PLP by HPLC are complementary to enzymatic determinations of PLP. An often used enzymatic method (47) for assaying plasma PLP is based on the coenzyme dependent decarboxylation of tyrosine catalyzed by L-tyrosine decarboxylase (EC 4.1.1.25). By using a well-resolved apo-enzyme preparation, it was shown that the reaction rate is directly proportional to the amount of PLP added to the reaction mixture. Conventionally, the reaction is monitored by CO2 liberation from L-tyrosine- Ci the liberated " C02 is trapped in a potassium hydroxide solution and subsequently quantitated by liquid scintillation counting. 

DAG and the remaining 3 subjects ingested TAG. One month later, the groups were reversed for the second examination. Changes in serum parameters were examined by analysing blood samples before eating the test emulsions, and 2 h, 3 h, 4 h, 6 h and 8 h afterwards. Serum lipid concentrations were measured by the conventional enzymatic method. Serum lipoprotein lipase (LPL) levels were measured by the method of Kobayashi et al. (1993) using anti-LPL antibody. Quantification of remnant-like lipoprotein particles (RLP) was carried out by the method of Nakajima et al. (1993, 1996). 

Typical LC molecules that exhibit SmC and/or SmCA phase are shown in Figure 1. As readily seen, the LC compounds consist of optically active 1,1,1-trifluoro-2-alkanols which contribute to the stabilization of the SmCA phase and thus play key roles of these LC materials. Accordingly methods for the l,l,l-trifluoro-2-alkanols have been the target of organic synthesis. Conventional retrosynthetic analysis of the trifluoro alcohols leads to (1) resolution of l,l,l-trifIuoro-2-alkanols by chemical or enzymatic methods, (2) asymmetric reduction of l,l,l-trifluoro-2-alkanones, or (3) asymmetric carbonyl addition of carbonaceous nucleophiles. Indeed, at present, the enzymatic resolution through the hydrolysis of the carboxylates of l,l,l-trifluoro-2-alkanols prevails. Other methods remain yet to be studied. 

Naturally, the first enzyme fixation methods [2] involved physical retention, and it was attempted to preserve, as far as possible, the integrity of the biological system. It was later realized that covalent fixation would prevent enzyme loss, and ensure long-lasting immobilization. The immobilization of enzymes is of prime importance. So long as the enzymes remain active, their immobilization enables repetitive and multiple determination. Conventional enzymatic methods discard the enzyme after each separate sampling. Enzymes are expensive because of the various extraction and purification stages they require, and we can immediately understand the economic interest of the new procedure, and its impact on the cost of sample analysis in automated systems. 

Process Va.ria.tlons. The conventional techniques for tea manufacture have been replaced in part by newer processing methods adopted for a greater degree of automation and control. These newer methods include withering modification (78), different types of maceration equipment (79), closed systems for fermentation (80), and fluid-bed dryers (81). A thermal process has been described which utilizes decreased time periods for enzymatic reactions but depends on heat treatment at 50—65°C to develop black tea character (82). It is claimed that tannin—protein complex formation is decreased and, therefore, greater tannin extractabiUty is achieved. Tea value is beheved to be increased through use of this process. 

There are several chemical compounds found in the waste waters of a wide variety of industries that must be removed because of the danger they represent to human health. Among the major classes of contaminants, several aromatic molecules, including phenols and aromatic amines, have been reported. Enzymatic treatment has been proposed by many researchers as an alternative to conventional methods. In this respect, PX has the ability to coprecipitate certain difficult-to-remove contaminants by inducing the formation of mixed polymers that behave similarly to the polymeric products of easily removable contaminants. Thus, several types of PX, including HRP C, LiP, and a number of other PXs from different sources, have been used for treatment of aqueous aromatic contaminants and decolorization of dyes. Thus, LiP was shown to mineralize a variety of recalcitrant aromatic compounds and to oxidize a number of polycyclic aromatic and phenolic compounds. Furthermore, MnP and a microbial PX from Coprinus macrorhizus have also been observed to catalyze the oxidation of several monoaromatic phenols and aromatic dyes (Hamid and Khalil-ur-Rehman 2009). 

The occurrence of more than one affected child in many of the families with galactosemia made it appear highly probable that this was a genetically determined disease. The mode of inheritance was worked out by the conventional methods of human genetics and, later, confirmed by biochemical studies of the families. The direct assay of enzymatic activity in heretozygotes for galactosemia must rank as one of the major contributions of biochemistry to the study of human genetics. 

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