Enzymatic reactions 382 INDEX

Figure 8.4. Main window of Gepasi. The main window of Gepasi consists of menus (File, Options, and Help), icons, and four tabs (Model definition, Tasks, Scan, and Time course). Activation of any of the tab opens an indexed page. At the start of Gepasi, the Model definition page is opened. Enter name of the metabolic pathway to the Title box. Click Reactions button to define enzymatic reactions (e.g., E + A+B = EAB for R1, EAB = EPQ for R2, and EPQ = E + P + Q for R3 shows 3 reactions and 7 metabolites), and then click Kinetics button to select kinetic type. Activate Tasks tab to assign Time course (end time, points, simufile.dyn), Steady state (simufile.ss) and Report request. Activate Scan tab to select scan parameters. Activate Time course tab to select data to be recorded and then initiate the time course run.

Electrochemical detection is inherently a chemical rather than a physical technique (such as ultraviolet, infrared, fluorescence, or refractive index). It is, therefore, not surprising to hnd that many imaginative postcolumn reactions have been coupled to LC-EC. These include photochemical reactions, enzymatic reactions, halogenation reactions, and Biuret reactions. In each case, the purpose is to enhance selectivity and therefore improve limits of detection. While simplicity is sacrihced with such schemes, there are many published methods that have been quite successful. 

The stereospecificity is an important property of enzymes and the reaction stereochemistry of enzyme catalysis is a vital index of the organization of the enzyme active site and details of its reaction mechanism. The following rules, which determine stereochemical uniformity in enzymatic reactions, have been proposed (Hanson and Rose, 1975). 

The enzymatic reaction kinetics on the HRP-catalyzed oxidation of p-cresol in aqueous 1,4-dioxane or methanol showed that the cataljdic turnover niunber and Michaelis constant were larger than those in water (235). Numerical and Monte Carlo simulations of the peroxidase-catalyzed polymerization of phenols were demonstrated (236). The simulations predicted the monomer reactivity and polymer molecular weight, leading to synthesis of polymers with specific molecular weight and index. In an aqueous 1,4-dioxane, the formation of monomer aggregate was observed (237), which might elucidate the specific polymerization behaviors in such a medium. 

As a result of the enzymatic degradation of proteins, key indexes change, ie, protein solubility indexes (PSI), peptide chain length (PCL), and protein solubility in 0.8 M TCA (TCA-index) (Fig. 14). Unpleasant bitterness was once a problem for some protein hydrolyzates. This problem can now be overcome by proper selection of the reaction parameters and the enzymes used. 

If the substances separated on a TLC plate are not directly visible and do not react to UV light, they can be caused to absorb light or to fluoresce by reaction with suitable reagents. In the case of biological reactions, the result can be obtained, for example, as the hemolytic index (HI) on coating the plate with blood-gelatin or as the measured values found from an enzymatic inhibition test. 

Casson models were used to compare their yield stress results to those calculated with the direct methods, the stress growth and impeller methods. Table 2 shows the parameters obtained when the experimental shear stress-shear rate data for the fermentation suspensions were fitted with all models at initial process. The correlation coefficients (/P) between the shear rate and shear stress are from 0.994 to 0.995 for the Herschel-Bulkley model, 0.988 to 0.994 for the Bingham, 0.982 to 0.990 for the Casson model, and 0.948 to 0.972 for the power law model for enzymatic hydrolysis at 10% solids concentration (Table 1). The rheological parameters for Solka Floe suspensions were employed to determine if there was any relationship between the shear rate constant, k, and the power law index flow, n. The relationship between the shear rate constant and the index flow for fermentation broth at concentrations ranging from 10 to 20% is shown on Table 2. The yield stress obtained by the FL 100/6W impeller technique decreased significantly as the fimetion of time and concentration during enzyme reaction and fermentation. 

---