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M Eigen

Publications and source records attributed to M Eigen.

At least 73 records · Page 4Linked to original sources
PubMed1981

Transfer-RNA: the early adaptor.

Evolutionary history of tRNA is studied by comparative sequence analysis of two specified tRNA's at various phylogenetic levels and of tRNA families within four different species. Criteria are developed that allow 1) to distinguish between convergent and divergent evolution, 2) to determine the mechanism of divergence and 3) to estimate the degree of randomization of the variable parts of the sequences. The conclusion of these investigations is that tRNA's represent ancient molecules that existed in the form of a mutant distribution prior to their integration into genomes.

Bacteria↗
PubMed1981

Transfer-RNA, an early gene?

The theory of self-reproductive molecular systems involves the consequence that translation must have started from a selected distribution of RNA molecules, that comprised GC-rich sequences of a length less than 100 nucleotides. This implies a joint function of messenger and adaptor, which both had to be recruited from the same mutant distribution. The reconstruction of tRNA precursors yields such a molecule showing some reverberation of a codon pattern GNC. These findings suggest that tRNA has been the earliest component of the translation machinery.

Base Sequence↗
PubMed1981

Comments on snake symbolism and mind-body relations.

In summary, the symbolic use of an object in part depends on which of its functional-structural qualities is emphasized in a given moment. For example, the snake may take on different symbolic meanings when emphasis is given to its eyes, tongue, fangs, anatomical form, or movement. Its various aspects constitute a complex system of references to unconscious (and conscious) mental and body self-configurations. These references frequently undergo transformations which make use of structurally related symbols. In the present paper, various aspects of the snake symbol were related to one another and to other symbolic transformations, including the elevator and flying. The structural principles underlying these analyses may be found to organize a wide range of phenomena and were here applied to Tausk's "influencing machine."

Animals↗
PubMed1981

Comments on "growth of a hypercycle" by King (1981).

The notion of hypercycles has been introduced (Eigen, 1971) in order to characterize a functional entity which integrates information stored in individual self-replicating elements. Commonly, these self-replicating elements compete, like polynucleotides do in test tube experiments (Spiegelman, 1971; Biebricher et al., 1981) or, like species do in nature. A single species is selected eventually together with its most frequent mutants and the less efficient competitors disappear. In order to suppress competition, specific coupling terms of second order - these are coupling terms which are proportional to the product of two population numbers or concentration - have to be introduced into the kinetic equations such a link has to extend to all members, requiring the formation of a closed catalytic cycle (Eigen and Schuster, 1979). The copying of polynucleotide sequences, like every transfer of information, can only occur with finite accuracy (Eigen et al., 1981). This physical restriction imposes a limit upon the content of information that can be transmitted. A higher content of information requires more precise replication. A more involved replication machinery, however, presupposes more information to build it. Thus, a single autocatalyst will not be able to increase its content of information over the given threshold. How does one escape from this vicious circle? Hypercycles present a solution to the problem: many information carriers coexist and may cooperate to build a more sophisticated and more precisely copying replication machinery. Optimization of growth rates has never been the goal for which hypercycles were conceived. Any first order process can proceed at a higher rate than a second order process if low enough concentrations are chosen. On the other hand, any realistic hypercycle involves both first and second order terms. At low concentrations first order terms provide for accumulation of material while at higher concentration second order terms stabilize cooperation. At which concentration level such a prevalence changes is a matter of quantitative values of rate parameters rather than of basic principle. An autocatalyst may outgrow a hypercycle under certain conditions but it can never solve the problem of integrating information.

Models, Chemical↗
PubMed1981

The area of faith in Winnicott, Lacan and Bion.

The area of faith is distinguishable from operations which primarily emphasize ego mastery and introjection-internalization processes. Faith is implicit in Winnicott's transitional experiencing and carried forward in object usage. In Bion faith is linked with openness to O or the (unknowable) ultimate reality of a session and is the operative principle of the psychoanalytic attitude. This paper emphasizes the play of faith in Winnicott's object usage and Bion's O. A certain faith is also required to tolerate the movement of meaning in Lacan's Symbolic order. Faith as a fundamental dimension is in tension with the defensive use of mastery and introjective-projective representational networks. In its various forms this complex tension is part of the structure of human life and constitutes the arena in which faith may evolve.

Consciousness↗
PubMed1980

Elementary step dynamics of catalytic hypercycles.

Two model systems for hypercyclic organisation constructed from a series of uni- and bimolecular reaction steps were studied under the condition of unlimited growth by means of qualitative analysis and numerical integration of the corresponding differential equations. It is shown that both models lead, within wide ranges of parameter and initial conditions, to the same characteristic dynamical behaviour as the elementary hypercycles and hypercycles with translation introduced in 1978 by Eigen and Schuster.

Kinetics↗
PubMed1979

Selection and self-organization of self-reproducing macromolecules under the constraint of constant flux.

We investigate the dynamic behavior of a set of self-reproducing macromolecules (e.g., polynucleotides) under conditions such that the fluxes of all monomer units into the system are kept constant. Such conditions might prevail in an evolution reactor or in certain naturally occurring situations. A general set of equations is developed to describe the behavior of both the macromolecule and the monomer concentrations. The question of how the rate of macromolecule synthesis varies with the monomer levels is discussed briefly. With the help of several physically reasonable approximations, we obtain an exact solution for a simplified constant flux system. Comparison with the corresponding system under the constraint of constant overall organization reveals important similarities, most notably in the existance and composition of quasispecies. Given the same set of physical and chemical parameters, a system subject to constant flux will always evolve toward selective equilibrium more slowly than under the constraint of constant organization.

Kinetics↗