Synergism explanation

To hydrolyze crystalline cellulose efficiently by enzymatic means, the inaccessibility of crystalline structures must be overcome. T. reesei and some other true cellulolytic microorganisms produce a cellulase complex that is capable of efficiently hydrolyzing crystalline cellulose. One explanation of this capability was first proposed by Mandels and Reese (7). In this model, two factors, Ci and C worked together to disrupt and hydrolyze cellulose. Ci first disrupted the crystalline structure of the cellulose while Cx attacked the available sites formed by Ci. In other words, Ci and C exhibit synergism in hydrolyzing cellulose. Since then, the combined action of cellobiohydrolase ( Ci ) and endoglucanase ( C ) has been identified as the source of the apparent synergism (6,26,55). 

A possible and most likely explanation for the low value of viscosity for the mixtures based on Equation 4.7 is the very different viscosity dependence on concentration for the peetin and LB gum solutions, and not a true antagonism. To work with these gum solutions at equal concentration and to detect some possible synergism or antagonism between them, we must take into account the viscosity-concentration dependence of dilute gum solutions over the range of concentrations of each gum in the mixture. 

Some results obtained by Storer (1968) using well-dialyzed polystyrene latices at pH 8.5 and mixtures of magnesium sulfate and sodium nitrate as the coagulating electrolytes are shown in Fig. 23. Distinct synergism was observed over the entire concentration range. The use of activities of the ions in the mixed system rather than concentrations, gave a reasonable explanation for the form of the data, bot it is also of interest that the discrete-ion treatment of Levine and Bell (1965) also predicts synergism for certain cases. 

A synergism between IAA and BR was also described by Katsumi (72) in green cucumber hypocotyl segments, and analysis by the PEST program showed the difference between data sets for IAA alone and IAA with fixed concentrations of BR can be accounted for by a change in the parameter RAMP, suggesting that the response capacity of the tissue to IAA is enhanced by BR (8). Possible explanations for this effect could be increased numbers of receptors for IAA, amplification of the LAA-induced signal, or its transmission, increased transcription or translation rates for LAA-induced protein synthesis, decreased turnover of mRNA or proteins, increased rates of delivery of cell wall components, etc. Much more research is needed to examine these possibilities. 

Various explanations for this synergism have already been proposed. Willeboordse and co-workers (6) explained the synergism by the coordination of the amine to the isocyanate in a tin-isocyanate-alcohol complex, thereby increasing the complex s stability as shown in Figure 1. 

Another supporting evidence for complex formation as a prerequisite to synergism was obtained from the study of the catalysis of phenyl isocyanate-butanol reaction by soluble organic cobalt compounds in presence and absence of DABCO catalyst. The results obtained are presented in Figures 4 and 5. It is evident that the combination of DABCO catalyst with divalent cobalt compounds shows synergistic effects while the trivalent cobalt acetylacetonate shows relatively low activity. The explanation of these observations is the structure of these compounds. 

Antioxidant Activity of Some Phenyl-Substituted Phenols (VII) in PP at 180°C (Oxygen-Uptake Test). In Table I the results obtained with some phenyl-substituted phenols are shown and compared with some well-known ferf-butyl-substituted phenols. A general conclusion from this table is the marked synergism between phenyl-substituted phenols and -activated thioethers compared with the ferf-butyl-substituted analog. Since the measurements are done in a closed tube, the influence of the volatility of the thiodipropionates is not reflected in the induction periods. An explanation for the anomalous behavior of phenyl-substituted phenols in synergistic mixtures can be found in the results of the model reactions, carried out with phenoxyl radicals and sulfides or sulfoxides (see "Model Reactions ). 

These data do not offer an explanation for the synergism in the prOpionic-butyric acid mixture. Steric factors seem to govern this type of catalysis. 

Carbon monoxide is an extremely weak Lewis base towards conventional Lewis acids. It does not complex with the boron trihalides, although it does yield a weak adduct H3B CO with diborane. On the other hand it forms numerous complexes with transition elements. The source of this difference is that in the latter complexes not only is the weakly donating a-orbital of CO involved, but also the 7C orbitals which can function as acceptors. The conventional explanation is that a synergic effect exists in which the n interaction removes electron density from the metal, allowing a donation from the ligand to be enhanced. 

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