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PubMed1993

The RNA-world and co-evolution hypotheses and the origin of life: implications, research strategies and perspectives.

The applicability of the RNA-world and co-evolution hypotheses to the study of the very first stages of the origin of life is discussed. The discussion focuses on the basic differences between the two hypotheses and their implications, with regard to the reconstruction methodology, ribosome emergence, balance between ribozymes and protein enzymes, and their major difficulties. Additional complexities of the two hypotheses, such as membranes and the energy source of the first reactions, are not treated in the present work. A central element in the proposed experimental strategies is the study of the catalytic activities of very small peptides and RNA-like oligomers, according to existing, as well as to yet-to-be-invented scenarios of the two hypotheses under consideration. It is suggested that the novel directed molecular evolution technology, and molecular computational modelling, can be applied to this research. This strategy is assumed to be essential for the suggested goal of future studies of the origin of life, namely, the establishment of a 'Primordial Darwinian entity'.

Biological Evolution↗
PubMed1999

Scanning tunnelling microscopy and molecular modelling of xanthine monolayers self-assembled at the solid-liquid interface: relevance to the origin of life.

The development of scanning tunnelling microscopy (STM) has allowed examination of inorganic crystalline surfaces and their interactions with organic adsorbates with unparalleled resolution. As a novel technique in origin of life studies, the application of STM is detailed with particular attention paid to the methods employed in the analysis of organic monolayer structures. STM imaging and molecular modelling of self-assembled monolayers of the purine base, xanthine, formed on the surfaces of graphite and molybdenum disulfide are presented as an example. The putative role of such structures in the origin of life is discussed.

Hydrogen Bonding↗
PubMed1989

Experimental studies in the origin of life.

Modern astronomy suggests that planets are plentiful in the Universe and that the conditions suitable for life are commonplace. Advances in biochemistry have pointed out the unity of the biosphere and lead to the belief that all life had a common chemical origin. Laboratory experiments indicate that almost all the building blocks of life can be synthesized under simulated primitive Earth conditions. The analysis of meteorites and the study of the interstellar medium indicate that molecules of biological interest are commonplace in the Universe, thus leading to the conclusion that the evolutionary process which has taken place on Earth may have also occurred elsewhere in the cosmos leading to extraterrestrial civilisations.

Astronomical Phenomena↗
PubMed1995

Thermal synthesis of amino acids and the origin of life.

The recent review by Marshall (1994) of the production of amino acids from the interstellar components, formaldehyde and ammonia, is placed in the larger context of the origin of life. Thermal energy, being ubiquitous in the Earth, emerges as the sole necessary form of energy. To appreciate the overview of the natural evolutionary sequence it is necessary to recognize stepwiseness in evolution, a principle that has however been often ignored. Since self organization of thermal protein to cells is instantaneous, but only one step in a geochemical ladder, individual steps may be regarded as instantaneous, while the sequence requires measurable time. Two steps indicated are extrusion of a hot, dry organic magma of amino acids --> peptides into an aqueous environment in which occurs a second step of self organization. In this paper, spinoffs of the defensible theory for the origin of life have been briefly reviewed as a fundamental consequence of nonrandom thermal copolymerization of amino acids.

Amino Acids↗
PubMed2000

Origin of life. Life as we don't know it.

There are two main groups of theories for the origin of life on Earth, the prebiotic broth theories and the hydrothermal theories, exemplified by the iron-sulfur world theory. In his Perspective, Wächtershäuser discusses the report by Cody et al., which provides key support for the latter proposal.

Carbon Monoxide↗
PubMed2000

RNA folding argues against a hot-start origin of life.

Opinion is strongly divided on whether life arose on earth under hot or cold conditions, the hot-start and cold-start scenarios, respectively. The origin of life close to deep thermal vents appears as the majority opinion among biologists, but there is considerable biochemical evidence that high temperatures are incompatible with an RNA world. To be functional, RNA has to fold into a three-dimensional structure. We report both theoretical and experimental results on RNA folding and show that (as expected) hot conditions strongly reduce RNA folding. The theoretical results come from energy-minimization calculations of the average extent of folding of RNA, mainly from 0-90 degrees C, for both random sequences and tRNA sequences. The experimental results are from circular-dichroism measurements of tRNA over a similar range of temperatures. The quantitative agreement between calculations and experiment is remarkable, even to the shape of the curves indicating the cooperative nature of RNA folding and unfolding. These results provide additional evidence for a lower temperature stage being necessary in the origin of life.

Hot Temperature↗
PubMed1987

Moral reflections on the new technologies: a Catholic analysis.

New technologies of conception bring into being beautiful babies. The wonder of these children, and of the technologies themselves, can tempt us to abbreviate ethical reflection on the moral appropriateness of initiating human life in this way. However, the moralists of the Catholic Church, along with many others, judge that human life should originate in acts of love between parents, not in productive acts of technologists. Scientific help for people desiring to generate a child out of their own being should be distinguished from scientific substitution for human acts of love in originating life. The child must be recognized as an equal, not as a product, subject to quality control. To radically alter our ways of generating human life without sufficient moral reflection is to generate human pain and moral dilemmas that we have not begun to fathom.

Catholicism↗
PubMed1998

Evolution of interstellar dust and its relevance to life's origin: laboratory and space experiments.

A scheme is presented for an analog investigation of long term irradiation of ices and organics following the cyclic evolution of interstellar dust. The irradiation is proposed to be performed at cryogenic temperatures on a space platform, and with an enhancement of the solar ultraviolet flux using a concave mirror, grating combination which eliminates the visual and infrared from the sample surface.

Carbon↗
PubMed1997

The origin of life: philosophical perspectives.

In this paper I consider the work which has been done on The Origin of Life in the last 100 years. It is my argument that a great deal of the underpinning of discussions on this topic have been more philosophical than anything based in brute experience or theory.

Animals↗
PubMed2003

[Problems of exobiology: the origin of life on Earth].

The basic problem of exobiology is origin and evolution of life as a space phenomenon. Consideration is given to the facts for the space origin, spreading in the interstellar space of and invasion of the surface of planets by organic compounds, constituents of archetypes of living systems. The authors bring up to discussion the issues of life development under the conditions of Earth, and formation of the main properties of the living organisms differing in the level of organization. Outlined are some international projects on exobiological research in experiments with bio-objects on space platforms.

Biological Evolution↗
PubMed1997

Titan and the origin of life on Earth.

The relevance of Titan to the study of pre-biotic chemistry and the origin of life on Earth will be addressed by an interdisciplinary group of Cassini/Huygens scientists using the different, but synergistic data sets obtained by NASA's Cassini Orbiter and ESA's Huygens Probe. Titan's special importance lies in the primitive chemically-reducing nature of its atmosphere Cassini/ Huygens instruments will determine what compounds form in this environment, and the results will be compared with models for pre-biological chemical evolution on Earth.

Atmosphere↗
PubMed1982

Clay and the origin of life.

Research concerning the possible role of clay in chemical evolution is reviewed. The probable importance of clays in the origin of life is assessed.

Amino Acids↗
PubMed2000

A system of two polymerases--a model for the origin of life.

What was the first living molecule--RNA or protein? This question embodies the major disagreement in studies on the origin of life. The fact that in contemporary cells RNA polymerase is a protein and peptidyl transferase consists of RNA suggests the existence of a mutual catalytic dependence between these two kinds of biopolymers. I suggest that this dependence is a 'frozen accident', a remnant from the first living system. This system is proposed to be a combination of an RNA molecule capable of catalyzing amino acid polymerization and the resulting protein functioning as an RNA-dependent RNA polymerase. The specificity of the protein synthesis is thought to be achieved by the composition of the surrounding medium and the specificity of the RNA synthesis--by Watson-Crick base pairing. Despite its apparent simplicity, the system possesses a great potential to evolve into a primitive ribosome and further to life, as it is seen today. This model provides a possible explanation for the origin of the interaction between nucleic acids and protein. Based on the suggested system, I propose a new definition of life as a system of nucleic acid and protein polymerases with a constant supply of monomers, energy and protection.

DNA-Directed RNA Polymerases↗