Physical Organic Chemistry and the Origin of Life Problem: A Personal Perspective (original) (raw)
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ChemInform, 2014
Organic chemistry is based on the classical concept of the molecule, which postulates that molecules have distinct physical shapes, sizes, structures, and are composed of atoms and chemical bonds. Although this concept is not consistent in some respects with what is suggested by quantum mechanics, it reveals a novel property of molecules: molecules are designable. Thanks to this property we can synthesize chemical compounds as we desire with precise control of molecular transformations. Organic synthesis, especially the highly selective synthesis of chiral substances, demonstrates that this concept is empirically adequate. It is also shown that organic chemistry is rational and autonomous as a science with regard to the Method of Analysis and Synthesis.
The Chemistry of Life’s Origins
He was trained in polymer chemistry at the University of Strasbourg. Dr. Brack received his M.S. in chemistry in 1962 and did his dissertation on polypeptide chemistry in 1970. He started his career at the Centre de Recherche sur les Macromolecules in Strasbourg (1963-1968) and moved to the Centre de Biophysique Moléculaire in Orléans in 1968. He spent one year (1975) at the Salk Institute for Biological Studies in San Diego. His field of expertise concerns the chemistry of the origins of life, as well as the search for life in the Solar System. He is a former president of the International Society for the Study of the Origin of Life (1996-1999) and is president of the European Exo/Astrobiology Network since 2001. He is Principal Investigator of two ESA space experiments: AMINO (on ISS EXPOSE) and STONE (artificial Martian meteorite experiments on FOTON). Professor Brack has published over 150 articles in peer-reviewed journals, 4 books and 15 sciencepopularizing articles in magazines.
Origins of Life: Chemical and Philosophical Approaches
Evolutionary Biology, 2015
In this article we address selected important milestones of chemical evolution that led to life. The first such milestone could be achieved by Oparin's model, which accounts for the early stages of chemical evolution. These occurred at the dawn of development of primitive chemical systems that were pre-RNA. Oparin's model consists of spontaneous formation of coacervates that encapsulate chemical matter, undergo primitive self-replication, and provide a pathway to a primitive metabolism. We review the experimental updates of his model from our laboratory and discuss types of selection that could have occurred in these primitive systems. Another major milestone in chemical evolution is the transition from abiotic to biotic. This has occurred later, after the RNA world evolved. A controversy of what life is interferes with the efforts to elucidate this transition. Thus, we present various definitions of life, some of which specifically include the requirements and mechanisms for this transition. Selfreplication is one of the major requirements for life. In this context we reexamine the question if viruses, which do not have capability to self-replicate, are alive. We draw on philosophy of Hegel, Aristotle, Rescher, Priest, and Fry to guide us in our endeavors. Specifically, we apply Hegel's law on quantity-to-quality transition to abiotic-to-biotic transition, Aristotle's philosophy to the definition of life, Priest's dialetheism to the question if viruses are alive or not, Fry's philosophy to the beginning of natural selection in chemical evolution, and Rescher's philosophy to the possible cognitive bias toward simple definitions of life.
Origins of Life: Chemistry and Evolution
Progress in understanding the origins of life will be enhanced if models and their predictions are clearly understood and explicitly articulated. Two distinct models can be used to explain the genesis of biopolymers during the origins of life. In one model, which has been pursued for nearly 50 years, RNA is the result of inherent chemical reactivities of prebiotic chemical species. RNA invented evolution. This model enables the prediction that if the conditions of the ancient earth are sufficiently constrained, chemists will discover the direct synthetic pathways that produced RNA. In a fundamentally different model, which is more recent, RNA and other biopolymers are proposed to be the result of prolonged, creative, selection-based changes that occurred during chemical evolution and overlap with early biological evolution. Evolution invented RNA. In this evolutionary model, inherent chemical reactivities are not necessarily relevant to the origins of life and do not predict biosynt...
Approaches to the Origin of Life on Earth
Life, 2011
I discuss briefly the history of the origin of life field, focusing on the "Miller" era of prebiotic synthesis, through the "Orgel" era seeking enzyme free template replication of single stranded RNA or similar polynucleotides, to the RNA world era with one of its foci on a ribozyme with the capacity to act as a polymerase able to copy itself. I give the history of the independent invention in 1971 by T. Ganti, M. Eigen and myself of three alternative theories of the origin of molecular replication: the Chemotron, the Hypercycle, and Collectively Autocatalytic Sets, CAS, respectively. To date, only collectively autocatalytic DNA, RNA, and peptide sets have achieved molecular reproduction of polymers. Theoretical work and experimental work on CAS both support their plausibility as models of openly evolvable protocells, if housed in dividing compartments such as dividing liposomes. My own further hypothesis beyond that of CAS in themselves, of their formation as a phase transition in complex chemical reaction systems of substrates, reactions and products, where the molecules in the system are candidates to catalyze the very same reactions, now firmly established as theorems, awaits experimental proof using combinatorial chemistry to make libraries of stochastic DNA, RNA and/or polypeptides, or other classes of molecules to test the hypothesis that molecular polymer reproduction has emerged as a true phase transition in complex chemical reaction systems. I remark that my colleague Marc Ballivet of the University of Geneva and I, may have issued the first publications discussing what became combinatorial chemistry, in published issued patents in 1987, 1989 and later, in this field.
Planetary organic chemistry and the origins of biomolecules
Cold Spring Harbor perspectives in biology, 2010
Organic chemistry on a planetary scale is likely to have transformed carbon dioxide and reduced carbon species delivered to an accreting Earth. According to various models for the origin of life on Earth, biological molecules that jump-started Darwinian evolution arose via this planetary chemistry. The grandest of these models assumes that ribonucleic acid (RNA) arose prebiotically, together with components for compartments that held it and a primitive metabolism that nourished it. Unfortunately, it has been challenging to identify possible prebiotic chemistry that might have created RNA. Organic molecules, given energy, have a well-known propensity to form multiple products, sometimes referred to collectively as "tar" or "tholin." These mixtures appear to be unsuited to support Darwinian processes, and certainly have never been observed to spontaneously yield a homochiral genetic polymer. To date, proposed solutions to this challenge either involve too much dire...
Chemistry & Biodiversity, 2007
During the last two decades, the common school of thought has split into two, so that the problem of the origin of life is tackled in the framework of either the replication first paradigm or the metabolism first scenario. The first paradigm suggests that the life started from the spontaneous emergence of the first, supposedly RNA-based replicators and considers in much detail their further evolution in the socalled RNA world. The alternative hypothesis of metabolism first derives the life from increasingly complex autocatalytic chemical cycles. In this work, we emphasize the role of selection during the prebiological stages of evolution and focus on the constraints that are imposed by physical, chemical, and biological laws. We try to demonstrate that the replication first and metabolism first hypotheses complement, rather than contradict, each other. We suggest that life on Earth has started from a metabolism-driven replication; the suggested scenario might serve as a consensus scheme in the framework of which the molecular details of origin of life can be further elaborated. The key feature of the scenario is the participation of the UV irradiation both as driving and selecting forces during the earlier stages of evolution.
The origins and physical roots of life’s dual – metabolic and genetic – nature
Life Science Press, 2017
This review paper aims at a better understanding of the origin and physical foundation of life's dual-metabolic and genetic-nature. First, I give a concise 'top-down' survey of the origin of life, i.e., backwards in time from extant DNA/RNA/protein-based life over the RNA world to the earliest, pre-RNA stages of life's origin, with special emphasis on the metabolism-first versus gene/replicator-first controversy. Secondly, I critically assess the role of minerals in the earliest origins of bothmetabolism and genetics. And thirdly, relying on the work of Erwin Schrödinger, Carl Woese and Stuart Kauffman, I sketch and reframe the origin of metabolism and genetics from a physics, i.e., thermodynamics, perspective. I conclude that life's dual nature runs all the way back to the very dawn and physical constitution of life on Earth. Relying on the current state of research, I argue that life's origin stems from the congregation of two kinds of sources of negentropy-thermodynamic and statistical negentropy. While thermodynamic negentropy (which could have been provided by solar radiation and/or geochemical and thermochemical sources), led to life's combustive and/or metabolic aspect, the abundant presence of mineral surfaces on the prebiotic Earth-with their selectively adsorbing and catalysing (thus 'organizing') micro-crystalline structure or order-arguably provided for statistical negentropy for life to originate, eventually leading to life's crystalline and/or genetic aspect. However, the transition from a prebiotic world of relatively simple chemical compounds including periodically structured mineral surfaces towards the complex aperiodic and/or informational structure, specificity and organization of biopolymers and biochemical reaction sequences remains a 'hard problem' to solve.
SORRY, DARWIN: CHEMISTRY NEVER MADE THE TRANSITION TO BIOLOGY
Darwin Under Siege: Life Comes from Matter vs. Matter Comes from Life - http://scienceandscientist.org/Darwin, 2011
The term biology is of Greek origin meaning the study of life. On the other hand, chemistry is the science of matter, which deals with matter and its properties, structure, composition, behavior, reactions, interactions and the changes it undergoes. The theory of abiogenesis maintains that chemistry made a transition to biology in a primordial soup. To keep the naturalistic ‘inanimate molecules to human life’ evolution ideology intact, scientists must assemble billions of links to bridge the gap between the inanimate chemicals that existed in the primordial soup and anatomically modern humans. Even though the proponents of a natural origin of life expressed much optimism for providing their theories, presently there is a detailed compilation of information seriously questioning this doctrine. This reductionistic ideology has always failed to answer two simple questions: (1) What is the minimum number of parts that are essential for a living organism to survive? (2) By what mechanism do these parts get assembled together? Evolutionists say a series of prebiotic processes and developments guide networks of dynamically linked small molecules and amphiphiles to form biological macromolecules, membraneous compartments, and finally primitive cells. However, none of these proposed pathways to life appears to be credible. The continuous advancement in various fields of science are not only providing major challenges to reductionistic ideology but are supplying increasing evidence for a systemic concept of life as an organic whole. Several leading researchers in the field of ‘origin of life’ are continually concluding that there are major scientific problems attached with all existing naturalistic ‘origin of life’ hypothesis. Only by taking into account all biological activities collectively as a system can a satisfactory elucidation of the living state be realized. In this present paper an attempt has been made to present a few significant challenges to the theory of abiogenesis based on the peer reviewed scientific literature. Subsequently, a non-reductionistic concept of life as a system is proposed as an alternative for resolving some of the problems inherent in origin of life research.