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PubMed1989

Chemical evolution and the origin of life: bibliography supplement 1985.

This bibliography is the seventeenth annual supplement to the comprehensive bibliography on the same subject which was published in Space Life Sci. 2(1970), 225-295; 3(1972), 293-304; 4(1973), 309-329 and in Origins of Life 5(1974), 505-527; 6(1975), 285-300; 7(1976), 75-85; 8(1977), 59-66; 9(1978), 67-74; 10(1980), 69-87; 10(1980), 379-404; 11(1981), 273-288; 12(1982), 93-118; 13(1983), 61-80; 15(1984), 55-69; 17(1987), 171-184; 17(1987), 185-206.

Chemical Phenomena↗
PubMed2000

Origin of life on earth and Shannon's theory of communication.

The genetic information system is segregated, linear and digital. It is astonishing that the technology of information theory and coding theory has been in place in biology for at least 3.850 billion years (Mojzsis, S.J., Kishnamurthy, Arrhenius, G., 1998. Before RNA and after: geological and geochemical constraints on molecular evolution 1-47. In: Gesteland, R.F. (Ed.), The RNA World: The Nature of Modern RNA Suggests a Prebiotic RNA, second ed. Cold Spring Harbor Laboratory Press, Boca Raton, FL). The genetic code performs a mapping between the sequences of the four nucleotides in mRNA to the sequences of the 20 amino acids in protein. It is highly relevant to the origin of life that the genetic code is constructed to confront and solve the problems of communication and recording by the same principles found both in the genetic information system and in modern computer and communication codes. There is nothing in the physico-chemical world that remotely resembles reactions being determined by a sequence and codes between sequences. The existence of a genome and the genetic code divides living organisms from non-living matter. If the historic process of the origin and evolution of life could be followed, it would prove to be a purely chemical process (Wächtershäuser, G., 1997. The origin of life and its methodological challenge. J. Theor. Biol. 187, 483-694). The question is whether this historic process or any reasonable part of it is available to human experiment and reasoning; there is no requirement that Nature's laws be plausible or even known to mankind. Bohr (Bohr, N., 1933. Light and life. Nature 308, 421-423, 456-459) argued that life is consistent with but undecidable by human reasoning from physics and chemistry. Perhaps scientists will come closer and closer to the riddle of how life emerged on Earth, but, like Zeno's Achilles, never achieve a complete solution.

Genetic Code↗
PubMed2005

Thermosynthesis as energy source for the RNA World: a model for the bioenergetics of the origin of life.

The thermosynthesis concept, biological free energy gain from thermal cycling, is combined with the concept of the RNA World. The resulting overall origin of life model suggests new explanations for the emergence of the genetic code and the ribosome. It is proposed that the first protein named pF(1) obtained the energy to support the RNA World by a thermal variation of F(1) ATP synthase's binding change mechanism. It is further proposed that this pF(1) was the single translation product during the emergence of the genetic machinery. During thermal cycling pF(1) condensed many substrates with broad specificity, yielding NTPs and randomly constituted protein and RNA libraries that contained self-replicating RNA. The smallness of pF(1) permitted the emergence of the genetic machinery by selection of RNA that increased the fraction of pF(1)s in the protein library: (1) an amino acids concatenating progenitor of rRNA bound to (2) a chain of 'positional tRNAs' linked by mutual recognition, and yielded a pF(1) (or its main motif); this positional tRNA set gradually evolved to a set of regular tRNAs functioning according to the genetic code, with concomitant emergence of (3) an mRNA coding for pF(1).

Energy Metabolism↗
PubMed2005

Biologically enhanced energy and carbon cycling on Titan?

With the Cassini-Huygens Mission in orbit around Saturn, the large moon Titan, with its reducing atmosphere, rich organic chemistry, and heterogeneous surface, moves into the astrobiological spotlight. Environmental conditions on Titan and Earth were similar in many respects 4 billion years ago, the approximate time when life originated on Earth. Life may have originated on Titan during its warmer early history and then developed adaptation strategies to cope with the increasingly cold conditions. If organisms originated and persisted, metabolic strategies could exist that would provide sufficient energy for life to persist, even today. Metabolic reactions might include the catalytic hydrogenation of photochemically produced acetylene, or involve the recombination of radicals created in the atmosphere by ultraviolet radiation. Metabolic activity may even contribute to the apparent youth, smoothness, and high activity of Titan's surface via biothermal energy.

Carbon↗
PubMed1998

The origin of life--how long did it take?

We do not understand the steps leading from the abiotic early earth to the RNA world. Consequently, we cannot estimate the time required for the origins of life. Attempts to circumvent this essential difficulty are based on misunderstandings of the nature of the problem.

Earth, Planet↗
PubMed1981

Ernst Haeckel's concept of an evolutionary origin of life.

In 1865/66 E. Haeckel for the first time suggested an evolutionary sequence in order to explain the origin of the first living cell. Haeckel's concept is compared with modern theories of the origin of life. It is evident that Haeckel has not as yet received the credit that he deserves for his evolutionary concept.

Biological Evolution↗
PubMed1993

Quality-adjusted life years: origins, measurements, applications, objections.

Quality-adjusted life years or QALYs are used to combine, in a single measure, information about the quantity and quality of life produced by a health intervention. They have been used as outcome measures in clinical trials and in cost-effectiveness analyses. This paper describes how QALYs are assessed and how they are used. Methodological and theoretical problems are discussed as are ethical objections to the utilitarian ethos underlying their use. It is concluded that QALYs are part of a technology that is still in development but, because of the lack of alternatives, they will certainly continue to be used. It is important to resolve the outstanding methodological issues and reach an ethical consensus to ensure that QALYs truly reflect community goals.

Australia↗
PubMed1995

Speculations on the origin of life and thermophily: review of available information on reverse gyrase suggests that hyperthermophilic procaryotes are not so primitive.

All present-day hyperthermophiles studied so far (either Bacteria or Archaea) contain a unique DNA topoisomerase, reverse gyrase, which probably helps to stabilize genomic DNA at high temperature. Herein the data relating this enzyme is reviewed and discussed from the perspective of the nature of the last detectable common ancestor and the origin of life. The sequence of the gene encoding reverse gyrase from an archaeon, Sulfolobus acidocaldarius, suggests that this enzyme contains both a helicase and a topoisomerase domains (Confalonieri et al., Proc. Natl. Acad. Sci., 1993, 90, 4735). Accordingly, it has been proposed that reversed gyrase originated by the fusion of DNA helicase and DNA topoisomerase genes. If reverse gyrase is essential for life at high temperature, its composite structure suggests that DNA helicases and topoisomerases appeared independently and first evolved in a mesophilic world. Such scenario contradicts the hypothesis that a direct link connects present day hyperthermophiles to a hot origin of life. We discuss different patterns for the early cellular evolution in which reverse gyrase appeared either before the emergence of the last common ancestor of Archaea, Bacteria and Eucarya, or in a lineage common to the two procaryotic domains. The later scenario could explain why all today hyperthermophiles are procaryotes.

Archaea↗
PubMed2004

Kinetics of organic transformations under mild aqueous conditions: implications for the origin of life and its metabolism.

The rates of thermal transformation of organic molecules containing carbon, hydrogen, and oxygen were systematically examined in order to identify the kinetic constraints that governed origin-of-life organic chemistry under mild aqueous conditions. Arrhenius plots of the kinetic data were used to estimate the reaction of half-lifes at 50 degrees C. This survey showed that hydrocarbons and organic substances containing a single oxygenated group were kinetically the most stable; whereas organic substances containing two oxygenated groups in which one group was an alpha- or beta-positioned carbonyl group were the most reactive. Compounds with an alpha- or beta-positioned carbonyl group (aldehyde or ketone) had rates of reaction that were up to 10(24)-times faster than rates of similar molecules lacking the carbonyl group. This survey of organic reactivity, together with estimates of the molecular containment properties of lipid vesicles and liquid spherules, indicates that an origins process in a small domain that used C,H,O-intermediates had to be catalytic and use the most reactive organic molecules to prevent escape of its reaction intermediates.

Carbon↗
PubMedDate not supplied

[Origin of life].

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Abortion, Legal↗
PubMed2003

One-pot TiO2-catalyzed synthesis of nucleic bases and acyclonucleosides from formamide: implications for the origin of life.

A novel one-pot TiO2-catalyzed synthesis of nucleobases and acyclonucleosides from formamide is reported. Since formamide can be formed under prebiotic conditions, these reactions have implications for the origin of life. While a number of purine derivatives have been found as products of non-TiO2-catalyzed reactions, important compounds that would not otherwise occur (namely, thymine, 5-hydroxymethyluracil, and acyclonucleosides) are formed in acceptable yields by TiO2-catalyzed reactions. Moreover, TiO2 selectively affects the rates of degradation of nucleobases, as single units and when embedded in polynucleotides.

Base Sequence↗
PubMed1979

A proposal concerning the origin of life on the planet earth.

The widely accepted Oparin thesis for the origin and early evolution of life seems sufficiently far from the true state of affairs as to be considered incorrect. It is proposed that life on earth actually arose in the planet's atmosphere, however an atmosphere very different from the present one. Because of an extremely warm surface, the early earth may have possessed no liquid surface water, its water being partitioned between a motten crust and a fairly dense atmosphere. Early preliving systems are taken to arise in the droplet phase in such an atmosphere. The early earth, which resembled Venus then and to some extent now, underwent a transition to its present condition largely as a result of the evolution of methanogenic metabolism.

Animals↗
PubMed1977

Symbiosis and the origin of life.

The paper uses chemical kinetic arguments and illustrations by computer modelling to discuss the origin and evolution of life. Complex self-reproducing chemical systems cannot arise spontaneously, whereas simple auto-catalytic systems can, especially in an irradiated aqueous medium. Self-reproducing chemical particles of any complexity, in an appropriate environment, have a self-regulating property which permits long-term survival. However, loss of materials from the environment can lead to continuing decay which is circumvented by physical union between different kinds of self-reproducing particles. The increasing complexity produced by such unions (symbioses) is irreversible so that the chemical system evolves. It is suggested that evolution by successive symbioses brought about the change from simple, spontaneously arising, auto-catalytic particles to complex prokaryotic cells.

Biological Evolution↗