Eigen evolution experiment

Since the first evolution experiments by Sol Spiegelman, Manfred Eigen, and coworkers, the field of directed evolution itself has evolved into a plethora of different methodologies that can hardly be covered comprehensively in a standard textbook. We nevertheless tried to provide a collection of protocols useful to the novice as well as to the scientist experienced in the field. We hope to provide a practical starting point and at the same time inspire scientists to develop their own variations on the evolutionary theme. 

The patterns of autocatalysis with respect to parabolic and exponential reaction courses, which strongly affect the conclusions of Eigen s evolution experiments concerning the decision criteria for mutant selection and coexistence [5 b, 40 h, k], can now be derived from the thermodynamic data of the matrix patterns and their reactivities, and offer quite new views, with autocatalytic cooperation between competitive species [40 k]. Separate from enzyme-catalyzed evolution experiments with RNA and DNA systems, basic questions of prebiotic behavior can for the first time become the subject of detailed experimental research [40 k, 43]. While continuing their studies on more complex autocatalysis patterns, von Kie-drowski et al. diagnosed modulation of molecular recognition as an operational deficit of earlier artificial self-replicational nucleic acid systems with regard to exponential reaction courses, and identified it as an ideal aim for future models [44]. On its way to the nucleoprotein system, evolution must have... 

The next feature that I would like to discuss is the notion of selection that is central to the concept of evolution. That selection occurs even at the level of prebiotic conditions has been well demonstrated by Eigen and his group. In these experiments it was shown that several RNA sequences compete and of the many possibilities only a small fraction of... 

The second phase, namely the self-organising mechanism of the molecular self-replication has been investigated by Eigen (1971) and his coworkers (Eigen Schuster, 1979) unifying the detailed results of biochemical experiments with mathematical models of chemical kinetics. Theoretical studies have initially been motivated by the test-tube experiments on RNA evolution (for an early review see Spiegelman (1971)). The molecular mechanism of RNA replication is still always being studied (Biebricher et aiy 1983). 

Selection can be studied appropriately and in great detail under conditions which allow a straightforward mathematical analysis (Eigen and Schuster, 1979 Schuster et al., 1980). A convenient system, more elaborate than serial transfer experiments or stirred flow reactors, consists of an evolution reactor (Fig. 12) which allows to control the concentrations of all important reactants or products. In the simplest case we keep these concentrations constant as well as the sum of all concentrations of polynucleotides. Then, the relative concentrations of autocatalysts are the only remaining variables. 

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