Minimal self-replicating model

Scheme 12.23 Minimal self-replication model. The synthesis of replicator R is accelerated by the binding of components Cl and C2 to form a ternary complex [C1-C2-R].

Fig. 5 (a) Synergistic constitutional relationships observed at two length scales within (b) a model minimal self-replicating DCL. For clarity, the growth/division cycles of micellar structures are not represented (adapted from [11])... 

A minimal model for self-replication is shown in Scheme 12.23. The replicator (R) must be able to recognise and bind at least two different precursor components (Cl and C2) in a ternary (three component) complex, and to accelerate their chemical reaction with each other to produce a product that is a copy of the original R. Such a simple system will always be in competition with the uncatalysed binary reaction of Cl and C2. 

It is, indeed, just this native complexity which for our today s chemistry provides provocation and stimulation, intimidation and temptation, love and hate and fate together. The present artificial systems still remain utterly outclassed by even the most primitive life forms such as RNA-viruses. The possibilities of describing natural selection behavior according to quasi-species distributions in the extreme multidimensionalities of sequence spaces [3d, e] are, for artificial systems, at best a very distant utopia. With all its early primi-tivity, but also with its promising inherent potential of minimal models of self-replication [6,7,9] and - just to follow - minima vita models [8], chemistry, nevertheless, is gaining new qualities by retracing transitions to life. 

Figure 22. (Bio)mesogens approaching pre-life states (7 a, 17, 18, 43] a) von Kiedrowski s and Orgel s minimal models of replication on the basis of self-complementary oligonucleotide DNA and RNA systems [44a-d, f-h] b) distant nucleic acid strand-analogs as matrix reaction models [7a, 18, 19, 39f-i] c) Rebek s self-replicational and evolutionary nucleoside analog model [45] d) von Kiedrowski s self-replicational amidinium-carboxylate model, being suggestive of exponential growth kinetics [44 e] e) Lehn s...

Almost all the examples of synthetic self-replicators reported during the past 25 years are based on the minimal model shown in Figure l(a). This minimal model of self-replication contains two distinct recognition-mediated... 

The model of self-replication discussed thus far involves self-complementary structures. However, template effects in a replication cycle can also operate in a reciprocal sense. In a minimal system, the template is self-complementary, whereas in a reciprocal system, a pair of templates are complementary to each other. Therefore, reciprocal replicating systems rely on two interlinked cross-catalytic cycles in which the two templates catalyze the formation of each other. The processes involved in reciprocal replication are encapsulated schematically in Figure 1(b). 

A minimal model for describing the kinetic mechanism of autocatalysis and self-replication (1-3)," as well as a full kinetic model explaining a wide range of behaviors under varying laboratory conditions were developed." ... 

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