Diversification processes

Imine metathesis has continued to be a popular exchange reaction for DCLs. Various groups have found novel systems in which the reaction can be applied, as well as interesting ways to halt the equilibration. For example, Wessjohann and coworkers have demonstrated that Ugi reactions can efficiently halt equilibration of an imine DCL, combining an irreversible diversification process with areversible library selection [24]. Xu and Giusep-pone have integrated reversible imine formation with a self-duplication process [25], and Ziach and Jurczak have examined the ability of ions to template the synthesis of complex azamacrocycles [26]. The mechanistically related reactions of hydrazone [27] and oxime [28] exchange have also been explored as suitable foundations for DCL experiments. 

Responses at the population level may clarify the potential role of chemosignals in the diversification of Liolaemus. The chemical profiles of the precloacal secretions of two populations of L. fabiani indicate that they show some level of differentiation (Escobar et al. 2003). However, populations of L. lemniscatus and L. tenuis did not show clear patterns of recognition of their own population vs. other populations apparently, chemosignals may not play a key role in the speciation process of Liolaemus (unpublished data). 

Diversification. First diversification occurs because resources are diverted toward less characteristic functions. Two specific areas where TSCA has had impacts are personnel and products. Research, development, manufacture, process and Industrial Hygiene personnel must meet early in the potential product s life to make predictions concerning areas specific to each. This tends to give anyone present a somewhat broader view of the products with which they are involved. 

Advances in soy protein processing technology have allowed extensive diversification of protein product applications. More sophisticated soy protein products now manufactured have more functionality, better performance, more consistency and better flavor than commercially available defatted soy flour and grits (50% protein dry basis). Among these products are improved textured soy flours, concentrates, and isolates (50%, 70% and 90% protein dry basis, respectfully), functional and non-functional soy protein concentrates (70% protein dry basis) and highly soluble, highly functional isolated soy proteins (90% protein dry basis) (6-8 14-18). 

Using hydrogen to produce electrical energy from fossil fuels in large centralised plants will contribute positively to achieving important reductions of C02 emissions, if this is combined with C02 capture and sequestration processes. Such plants will also help to increase the diversification of resources, since a variety of fossil feedstocks can be used, including resources such as coal and waste that otherwise cause major impacts on the environment, as well as biomass. 

Because the opportunities for controlled chain growth are more restricted in inorganic than in organic systems, an alternative approach to polymer synthesis becomes appealing. This involves the use of substitution processes carried out on a preformed reactive polymeric intermediate. In this way molecular diversity can be introduced by different substitution reactions rather than by a diversification of the polymerization process. 

We may hypothesize for the present that columnar cacti produce alkaloids as a general deterrent to herbivory, and triterpenoid glycosides and associated hydrolytic glycosidases as a specific toxification mechanism against specialist Drosophila species. Radiation and diversification of triterpenoids may have occurred in response to continued interaction between the cacti and Drosophila This process is dependent upon coevolution with specialized yeasts which may interfere with hydrolysis of triterpenoids or hydrolyze individual compounds selectively. 

Glycoside diversification also has occurred in the coevolution of monarch butterflies and milkweeds (7). It may be desirable to relate the toxicity of cardenolides to the hydrolytic capabilities of susceptible and nonsusceptible insects. Cardenolides from Rsclepias species can be hydrolyzed by 3-glucosidases present in the plant (6), yet specialized Danans species are able to sequester these compounds, a process wh ich requires control of hydrolysis. 

In order to understand fully the importance of these chemical factors, it is necessary to consider the processes which are probably responsible for their diversification. A mechanism of coevolution of insects and plants was set forth eloquently by Erlich and Raven (4). According to their hypothesis, angiosperms produced a series of chemical compounds which were not directly related to their basic (or primary) metabolic pathways, but which were otherwise not harmful to the plants growth and development. 

The former example is a radical innovation, not only because it allowed significant changes in message reminders and adhesives, but also because it was completely unexpected. The diversification of Post-It notes into different sizes and colors is an example of incremental innovation, which involves step-by-step changes and improvements to existing products or processes. Radical innovations are far less common, though their effects are farther reaching over both society and history. 

The establishment of plant integrated defenses involves the preferential evolutionary retention and production of those SCs exerting synergistic toxic effects and is possible only if a diversification of secondary metabolism in a given plant has previously occurred. This preliminary diversification of secondary metabolism could be mediated via the classical reciprocal co-evolutionary interactions between a host plant and its major pests, as predicted by the chemical arms race model (Beren-baum and Zangerl, 1996). The PICD hypothesis is consequently not an exclusive evolutionary hypothesis because it is compatible with and dependent on other evolutionary processes. The contribution of the PICD hypothesis is to provide both a functional explanation for the diversity of SCs within plants (Romeo et al, 1996) and a reconciliation between different evolutionary models. 

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