Chemical Co-evolution Model

The Chemical Co-evolution Model was based on the assumption that every NP possessed (or had possessed at some stage in evolution) some biological activity that enhanced the fitness of the producer. This assumption is not supported by experimental evidence and the assumption has no theoretical basis. Extensive studies of collections of both synthetic chemicals and NPs have shown that the probability of any one chemical structure possessing potent, specific biological activity is very low. These experimental findings are supported by the current imderstanding of the way in which small molecules interact with proteins to bring about biomolecular activity. 

NPs serve many roles in influencing the species-species interactions—the Chemical Co-evolution Model... 

As evidenced by the quotation at the beginning of this chapter, by the end of the twentieth century, there was still no winner in the race to provide a imiversal model to explain the evolution of NP chemical diversity but the Chemical Co-evolution Model was well ahead. Indeed, many of its advocates considered the race won. Certainly, this model had many attractions but it had some worrying weaknesses. 

The first weakness was that the Chemical Co-evolution Model was least convincing when applied to the most diverse, most ancient NP producers—the microbes. As explained above, many microbiologists simply did not find the model convincing when applied to microbes because very little real evidence for the model came from studies of microbes. The main evidence arising from studies of microbes was that some... 

The decision to write a book on the origin (or origins) of life presupposes a fascination with this great problem of science although my first involvement with the subject took place more than 30 years ago, the fascination is still there. Experimental work on protein model substances under simulated conditions, which may perhaps have been present on the primeval Earth, led to one of the first books in German on Chemical and Molecular Evolution Klaus Dose (Mainz) had the idea of writing the book and was my co-author. 

Although Co(Ni)MoSx /A1203 and related catalysts have been used commercially for more than 70 years, the exact chemical nature and structure of the active species are still not known. Many models and theories have been put forth and argued in the literature for almost the same length of time. There have been many excellent reviews that summarize in detail the evolution of theories of the structures of these catalysts (1-3, 9, 10) and there is little need to repeat in detail the contents of those reviews in this article. However, for ease of understanding the following discussion, the various models that have been proposed are illustrated in Fig. 16. 

What the mechanistic baseline provided by a model reaction does do is to suggest where molecular evolution may have necessarily started, although it must be remembered that substrates and enzymes have co-evolved so that the chemical scope of a primitive substrate may not be that of a modem substrate. Furthermore, a model-reaction mechanism may indicate what processes it was necessary for an enzyme to avoid in order to open the way for a comparatively unfavorable reaction to be catalyzed. One of the most striking examples is provided by the recent studies of Kluger and his coworkers of the unexpected chemical properties of the cofactor thiamin diphosphate [25-29]. Although this work has nothing explicitly to do with... 

---