Synergism between additives

Synergism between a-arabinosidase, xylanase and j8-xylosidase has been demonstrated in the hydrolysis of wheat straw arabinoxylan with purified enzymes of T, reesei (71). > en only xylanase and )8-xylosidase were used in the hydrolysis, the xylose yield was only 66% of that produced by the whole culture filtrate at the same activity levels of these two enzymes, and no arabinose was produced. Addition of a-arabinosidase increased the yields of both xylose and arabinose. Enhanced hydrolytic action of hemicellulolytic or pectinolytic enzymes in the hydrolysis of alfalfa cell wall polymers by addition of Ruminococcus albus a-arabinosidase has also been reported (37). 

When two compounds exert the same action by acting at different sites, their interaction will often result in a synergistic effect but a simple additive effect is also a possibility (the synergism between smoking and asbestos exposure is the classical example). 

Interferon induction in normal and leukemic lymphocyte cultures with tilorone has been observed50. The interferon response observed in normal lymphocyte cultures appeared to be correlated with the toxic effect of tilorone. The effect observed in leukemic cultures required higher concentrations of tilorone, but, similarly, appeared to be related to cell viability. Tilorone has been reported to stimulate production of interferon by itself in mouse embryo fibroblasts and, in combination with poly rl poly rC/DEAE-dextran in mouse L929 cells51. Human foreskin fibroblasts were not stimulated. The degree of synergism between tilorone and the nucleotide-dextran complex was proportional to the concentrations of tilorone and poly rl/poly rC and was influenced by the times of addition of the compounds relative to each other. 

Achayuthakan et al. (2006) studied vane yield stress of Xanthan gum-stareh dispersions. The intrinsic viscosity of Xanthan gum was determined to be 112.3 dl/g in distilled water at 25°C. In addition, the size of the granules in the dispersions of the studied starches waxy maize (WXM), cross-linked waxy maize (CWM), and cold water swelling (CWS) were determined. The values of yield stress of the starch-xanthan dispersions relative to those of the starch-water dispersions (YSA"S0) and relative mean granule diameters (D/DO) plotted against values of c[ ] of xanthan gum are shown in Figure 4-42. With the values of YS/YSO being less than 1.0, there was no synergism between CLWM starch and xanthan gum. 

In addition to familiar phenomena such as these, new phenomena arise because of the synergism between the properties of the polymer and those of the particle filler. One such synergistic effect is enhanced shear thinning, which occurs because the shear rate experienced by the polymer confined between two particles can be much larger than the overall imposed shear rate (Khan and Prud homme 1987). Another general observation is that the filled melt is often effectively less elastic than the polymer alone, evidently because the filler enhances the viscosity more than it does the first normal stress difference Ni (Han 1981 Han et al. 1981). Thus, Fig, 6-38 shows that at fixed shear stress the first normal stress difference Nj for polypropylene decreases upon addition of CaC03 particles. ... 

Tobacco smoke. Tobacco smoke produces particulate matter that acts as an adsorption site for toxic vapors)26 In addition to particulates, tobacco smoke produces more than 4000 individual toxic compounds, including 43 known carcinogens. 27 Many of the toxic effects of tobacco smoke that have been established empirically cannot be ascribed to individual compounds in that smoke. With more than 4000 different toxins, the number of mixtures possible is incalculable. Numerous examples of synergism between tobacco smoke and other toxicants have been identified. These include tobacco smoke and asbestos or other mineral fibers, I28 29 alcohol, I30 31 organic solvents, 32 biological... 

In vitro observations have demonstrated a marked synergism between PKC and Rho or Arf in the activation of PLDl [11, 56]. The molecular basis of this synergism is unknown, but binding of these regulators to the phospholipase must induce conformational changes that interact to produce enhanced activation. As indicated elsewhere in this chapter, PKC interacts with the N-terminal region of PLDl, but probably has an additional site(s). Rho binds to a sequence in the C-ter-minus, but the site of interaction of Arf is unknown. 

Intriguingly, in vitro data suggest a potential synergism between glatiramer acetate and interferon-/ . Given the cost of these therapies, as well as the potential for additive adverse effects, this therapeutic combination cannot be recommended until clinical evidence demonstrating benefit is available. A study that will compare glatiramer acetate alone with interferon-/ - a (Avonex) alone versus a combination of the two has just been funded by NIH and is underway, with results expected in several years. 

Many in vitro studies have firmly established a synergism between sulbactam and various P-lactam antibiotics including piperacillin, amdinocillin, ampicillin, and penicillin G. These studies included bacterial strains resistant to ampicillin or penicillin G alone, which became sensitive upon addition of sulbactam. Carbenicillin-resistant Pseudomonas, however, was not potentiated. 

Many other factors influence the reduction. These include the tendency of the catalyst to agglomerate, addition of a promoting substance, synergism between two catalysts, the temperature of the reaction, the ratio of hydrogen to compound being reduced, the pressure of hydrogen gas, the preparation method, and the age of the catalyst and the number of times it has been recycled. ... 

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