Amino Acids And The Asymmetry Of Life

"How did life originate and why were left-handed molecules selected for its architecture?" This question of high public and interdisciplinary scientific interest is the central theme of this book. It is widely known that in processes triggering the origin of life on Earth, the equal occurrence, the parity between left-handed amino acids and their right-handed mirror images, was violated. The balance was inevitably tipped to the left – as a result of which life's proteins today exclusively implement the left form of amino acids. Written in an engaging style, this book describes how the basic building blocks of life, the amino acids, formed. After a comprehensible introduction to stereochemistry, the author addresses the inherent property of amino acids in living organisms, namely the preference for left-handedness. What was the cause for the violation of parity of amino acids in the emergence of life on Earth? All the fascinating models proposed by physicists, chemists and biologist are vividly presented including the scientific conflicts. The author describes the attempt to verify any of those models with the chirality module of the ROSETTA mission, a probe built and launched with the mission to land on a comet and analyse whether there are chiral organic compounds that could have been brought to the Earth by cometary impacts. A truly interdisciplinary astrobiology book, "Amino Acids and the Asymmetry of Life" will fascinate students, researchers and all readers with backgrounds in natural sciences. With a foreword by Henri B. Kagan.

This book provides an interdisciplinary review of one of the great unsolved mysteries that has fascinated scientists for over 150 years: the origin of chirality in biomolecules. It was Pasteur who first initiated the search for a deterministic theory to explain the 'handedness' of biomolecules. His theory, that a 'dissimetric' force was involved, was correct in essence but he never saw the fruits of his labour. Current thinking tells us that asymmetry in the universe has its origins in the forces that unfolded after the Big Bang and, more specifically, the weak force. Being 'left handed', the weak force imprinted its signature on the evolving Universe. However, at the molecular level, the weak force does not provide a straightforward explanation of biomolecular homochirality. In fact, it is yet to be proved beyond doubt that a causal link exists at all. Many alternative theories have been put forward, some of them resting on solid ground, but all lacking definitive experimental evidence to back them up. Some postulate that the handedness of molecules in the biosphere arose by chance but this is hard to test. Others rely on discovering life on similar planets and making comparisons with Earth. Alternative theories have emerged from a range of backgrounds including geology, biology, chemistry, physics and astronomy. Current advances in fields as diverse as space exploration, prebiotic chemistry and high-energy physics may help to provide an answer. Important pieces of information will come from observations at the two frontiers of science: outer space and the subatomic world. Observation of distant planets, galaxies, and even actual sampling of celestial objects from beyond the solar system are projects currently underway. At the other end of the spectrum, there are experiments that study the elemental properties of matter, such as symmetry, and interactions with the fundamental forces. All these efforts will render their fruits soon. This volume unifies all the theories of the origin of biomolecular homochirality together in one source. The various chapters focus on chance mechanisms, physical forces such as the 'weakinteraction', fluid dynamics, amplification of chirality, the organic contents of meteorites and comets and, finally, the physical view of an intrinsically asymmetric universe. This complete, interdisciplinary review of an intriguing subject condenses a large and disparate range of contributions from journals in almost every scientific field. The various theories have been organized, interrelated and explained in a unified way. One of the book's strengths is its extensive use of graphic material to aid understanding the many subjects covered. It is fundamental, comprehensive and structured to be accessible for educational purposes.

In 1978, Fred Hoyle proposed that interstellar comets carrying several viruses landed on Earth as part of the panspermia hypotheses. With respect to life, the origin of homochirality on Earth has been the greatest mystery because life cannot exist without molecular asymmetry. Many scientists have proposed several possible hypotheses to answer this long-standing L-D question. Previously, Martin Gardner raised the question about mirror symmetry and broken mirror symmetry in terms of the homochirality question in his monographs (1964 and 1990). Possible scenarios for the L-D issue can be categorized into (i) Earth and exoterrestrial origins, (ii) by-chance and necessity mechanisms, and (iii) mirror-symmetrical and non-mirror-symmetrical forces as physical and chemical origins. These scenarios should involve further great amplification mechanisms, enabling a pure L- or D-world.

Until half a century ago, it was assumed that the forces of nature were symmetric and that they did not distinguish between right and left, between image and mirror image. The discovery of the violation of parity in 1956 was more than a sensation, for some it was a shock. It implied that the universe displays handedness, or chirality, and that it is fundamentally asymmetric. Remarkably, a most striking asymmetry is encountered in the realm of biology. Living organisms contain proteins built almost exclusively from L-amino acids, and nucleic acids derived from D-sugars only. Yet a mirror-image biochemistry, based on D-amino acids and L-sugars is, from a purely chemical standpoint, entirely conceivable. Where, then, does this extraordinary natural selectivity come from? Is it directly, or indirectly, connected to the universal violation of parity? This book is meant as a brief review of the various manifestations of handedness, or chirality, in the universe. It does not attempt to present a solution to basic questions which perhaps will never be unambiguously and conclusively answered. Rather, it is an excursion through nature, to observe and recognize how the chirality manifests itself at different structural levels. The excursion starts in the chemistry and physics laboratory. Then a journey into outer space and back in time is undertaken. After a return to our planet Earth, the focus is on the development of living organisms. The text should be accessible to anyone having the equivalent of a first-year university instruction in physics and chemistry. It is also hoped that a layperson with a more modest scientific formation may gain a general impression of the basic asymmetry in nature and of the fundamental significance of chirality. Mathematical expressions, wherever they occur, may then be overlooked. Some more difficult sections may be skipped. A Glossary preceding the Subject Index should be helpful.

This book collects papers presented at a workshop taking an interdisciplinary look at methods designed to detect life on other planets. It serves as a reference to scientists and instrument developers working in the field of in-situ and remote life detection.

Creating the Molecules of Life discusses origins, including the Big Bang, and the origin of the elements. With a complete presentation and explanation, this book provides evidence that the molecules of life are produced in outer space and how the SNAAP model purports to explain that origin. Extremophiles, which explains that evolution is robust enough to create life forms in a wide variety of conditions, is also presented. Readable for those at the upper undergraduate level, mathematics associated with coupling the nuclear spins to the molecular chirality is discussed. An accompanied appendix is provided to support mathematics.

Early History of the Recognition of Molecular Biochirality, by Joseph Gal, Pedro Cintas Synthesis and Chirality of Amino Acids Under Interstellar Conditions, by Chaitanya Giri, Fred Goesmann, Cornelia Meinert, Amanda C. Evans, Uwe J. Meierhenrich Chemical and Physical Models for the Emergence of Biological Homochirality, by son E. Hein, Dragos Gherase, Donna G. Blackmond Biomolecules at Interfaces: Chiral, Naturally, by Arántzazu González-Campo and David B. Amabilino Stochastic Mirror Symmetry Breaking: Theoretical Models and Simulation of Experiments, by Celia Blanco, David Hochberg Self-Assembly of Dendritic Dipeptides as a Model of Chiral Selection in Primitive Biological Systems, by Brad M. Rosen, Cécile Roche, Virgil Percec Chirality and Protein Biosynthesis, by Sindrila Dutta Banik, Nilashis Nandi