Inhibition side chain length

Fig. (6 a). Influence of the position of the side-chains on the phenylene ring of bis(4-trimethylammoniobutyl)benzene (upper) and of the side-chain length of bis-trimethylammonium derivatives (lower) on neuromuscular blocking activity. The percentage inhibition of nerve-stimulated twitch response in mouse phrenic nerve-diaphragm muscle is plotted against the log concentration. The values represent means S.E.M. (n = 4-7). 

Another important characteristic of inhibitors is the time of their inhibition action. If an inhibitor is consumed only in chain termination reactions, this time is determined by the initial concentration [InH]0, stoichiometric coefficient of inhibition / and Vj. In this case, the rate of inhibitor consumption is vInH = v //. Side reactions of InH with dioxygen and hydroperoxide shorten the inhibitory period and increase the rate of inhibitor consumption. Therefore, an inhibitor is efficient when it provides a minimal chain length v and its own loss in side reactions w is low. Assuming that an efficient inhibitor has w < 0.25, we get the inequality 4k 2[InH][02] < v which can be transformed, by substituting the correlation equation from Table 14.7, into the following equation... 

Through a comparison of the activities of the nine natural and synthetic compounds in Table I, certain functionalities appeared to be important in the efficacy of the isobutylamides to inhibit the growth of the lepidopterous larvae. These functionalities included the chain length, presence of the methylenedioxy moiety, the number of the side chain double bonds, and the stereochemistry of the side chain. Combinations of these functionalities would likely enhance the activity. For instance, Miyakado et al.H found that addition of the methylenedioxy moiety to pellitorine (4) increased its toxicity when topically applied to adults of the beetle, Callosobruchus chinensis. 

The phenomenon of catalyst-inhibitor conversion1 2,143,356 may be understood and critical concentration of metal can be deduced by reference to Eq. (280). If decomposition of the hydroperoxide is the source of initiation, it must be formed as rapidly as it is consumed to maintain a steady rate. If termination by metal complex predominates, a steady state occurs when the right-hand side of Eq. (280) equals unity. No oxidation will occur when this quantity is less than unity. Hence, catalyst-inhibitor conversion is observed as the metal concentration is increased to the point that the chain length becomes less than unity. If termination occurs by the bimolecular reaction of peroxy radicals, a chain length of less than unity will result in the depletion of the hydroperoxide until the rate of initiation has decreased to the point where the chain length is unity again. No inhibition is expected or observed. 

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