Showing papers on "Homochirality published in 1991"
TL;DR: In this article, an extraterrestrial scenario for the production of terrestrial chirality was proposed, in which circularly polarized synchrotron radiation from the neutron star remnant of a supernova interacts with the organic mantles on interstellar grains, producing chiral molecules by the partial asymmetric photolysis of racemic constituent in the mantles, after which the interstellar grains with their enantiomerically enriched mantles are transported to Earth either by direct accretion or through cometary impact.
Abstract: The unique chirality of biomolecules is reviewed, and the prebiotic requirement for the absolute chiral homogeneity of such molecules prior to their capability of self-replication is emphasized. Biotic and abiotic theories embracing both chance and determinate mechanisms which have been proposed for the origin of terrestrial chiral molecules are briefly summarized and evaluated, as are abiotic mechanisms for the subsequent amplification of the small enantiomeric excesses (e.e.s) in the chiral molecules which might be formed by such processes. While amplification mechanisms are readily validated experimentally and are potentially viable on the primitive Earth, it is concluded that all terrestrial mechanisms proposed for the origin of chirality have one or more limitations which make them either intrinsically invalid or highly improbable in the chaotic and turbulent environment of the prebiotic Earth. To circumvent these difficulties we have proposed an extraterrestrial scenario for the production of terrestrial chirality in which circularly polarized synchrotron radiation from the neutron star remnant of a supernova interacts with the organic mantles on interstellar grains, producing chiral molecules by the partial asymmetric photolysis of racemic constituent in the mantles, after which the interstellar grains with their enantiomerically enriched mantles are transported to Earth either by direct accretion or through cometary impact. At this point one of the known terrestrial e.e. enrichment mechanisms could promote the small extraterrestrially produced e.e.s. into the state of chiral homogeneity required for self-replicating biomolecules.
42 citations
TL;DR: It is demonstrated that self-replication could originate only on the basis of homochiral structures, possessing stereospecific (enzymatic) activity and it is suggested that homochirality is a necessary condition for the origination of biological specificity and plays a fundamental role in the formation of structures capable of self-Replication.
Abstract: The problem discussed in this paper is the connection between the unique property of biopolymers (proteins, DNA and RNA), i.e. homochirality, and their main functional property, i.e. self-replication. Our approach is based on an analysis of the conditions for the origination of the mechanism of self-replication of chiral polymers. It is demonstrated that self-replication could originate only on the basis of homochiral structures, possessing stereospecific (enzymatic) activity. It is also shown that complete breaking of the mirror symmetry of the organic medium is required both at the stage of polymeric takeover and at the stage of formation of structures possessing stereospecific activity. This requirement is satisfied only in the framework of the mechanism of spontaneous symmetry breaking i.e. the mechanism of non-equilibrium phase transition from the racemic state of the organic medium to the chirally pure one. The results obtained suggest that homchirality is a necessary condition for the origination of biological specificity and plays a fundamental role in the formation of structures capable of self-replication.
23 citations
TL;DR: In this paper, N-protected L-aminoacids are convenient derivatizing reagents for enantiomeric excess determination of chiral 1-hydroxyalkylphosphonic acids by the 31P NMR spectroscopy.
Abstract: N-protected L-aminoacids are convenient derivatizing reagents for enantiomeric excess determination of chiral 1-hydroxyalkylphosphonic acids by the 31P NMR spectroscopy. 1-Hydroxyalkylphosphonic acid esters coupled with N-protected L-aminoacids by means of the DCC method give the diastereoisomers which are quantitatively distinguishable in the 31P NMR spectra. The values of 31P NMR nonequivalence (0.06–0.60 ppm) differ with the change of the L-aminoacids and the protecting groups. The easily available Boc-L-Val and Boc-L-Phe in optically pure form seem to be promising chiral derivatizing agents. The measured enantiomeric excess of preweighed, enantiomerically enriched samples are in excellent agreement with the expected values.
16 citations
01 Jan 1991
TL;DR: In this paper, the authors present a theory on the origin of chirality in organic chemistry and its application in the field of chemical synthesis, including the use of biocatalysts.
Abstract: 1 Parity Violation in Atomic Physics.- 1.1 Introduction.- 1.2 Parity.- 1.3 Elementary Particles and Forces.- 1.3.1 Leptons and Quarks.- 1.3.2 Forces and Interactions.- 1.3.3 Spin and Helicity (Chirality).- 1.3.4 Unified Theory of Weak and Electromagnetic Interactions ("Standard Model").- 1.4 Parity-Violating Effects in Atoms.- 1.4.1 Phenomenology.- 1.4.2 Experiments.- 1.5 References.- 2 Theories on the Origin of Biomolecular Homochirality.- 2.1 Introduction.- 2.2 Observability of Chiral Molecular Structures.- 2.3 Kinetic Models for Unstable Equilibrium.- 2.4 Kinetic Models with Instrinsic Asymmetry.- 2.5 Parity-Violating Energy Differences Between Enantiomers.- 2.6 Homochirality from Stochastic Equations.- 2.7 References.- 3 Chirality and Group Theory.- 3.1 Introduction.- 3.2 The Principle of Pairwise Interactions.- 3.3 The Theory of Chirality Functions.- 3.4 The Approximation Methods.- 3.5 Determining the Lowest-Degree Chirality Polynomials.- 3.6 Qualitative Completeness and Supercompleteness.- 3.7 Counting Enantiomeric Pairs.- 3.8 References.- 4 Helicity of Molecules - Different Definitions and Application to Circular Dichroism.- 4.1 Introduction.- 4.2 The Ideal Finite Helix.- 4.3 Real Molecules or Parts of Them, Fractions of a Helix.- 4.4 Rules.- 4.4.1 The Torsional-Angle-Rule (CIP).- 4.4.2 The IUPAC-Axis-Tangent-Rule.- 4.4.3 The Two-Tangent Rule.- 4.4.4 The Spade-Product Rule.- 4.4.5 The Spiral-Staircase-Rule.- 4.5 Some Applications.- 4.6 Summary.- 4.7 References.- 5 Anomalous Dispersion of X-Rays and the Determination of the Handedness of Chiral Molecules.- 5.1 Introduction.- 5.2 "Normal" X-Ray Diffraction.- 5.2.1 Scattering from a Crystal.- 5.2.2 Friedel's Law and When It Breaks Down.- 5.2.3 Physical Origin of Anomalous Scattering.- 5.3 Past, Presence and Future Use of Anomalous Scattering.- 5.3.1 Outlook.- 5.4 References.- 6 Chirality in Organic Synthesis - The Use of Biocatalysts.- 6.1 Chirality in Organic Chemistry and Biochemistry.- 6.1.1 Explanation of Basic Terms.- 6.1.2 Comparison of Properties: Enantiomers and Diastereomers.- 6.1.3 The Importance of Enantiomeric Purity.- 6.1.4 Methods of Obtaining Enantionerically Pure Chiral Compounds.- 6.2 Biocatalysts in Organic Chemistry - General Remarks.- 6.2.1 Enzymes.- 6.2.2 Whole Cell Systems.- 6.2.3 Types of Selectivities Achieved.- 6.3 Enzymes.- 6.3.1 Classes and Nomenclature.- 6.3.2 Properties and Stabilities.- 6.3.3 Coenzymes.- 6.3.4 Enzyme Mechanisms.- 6.3.5 Active Site and Enzyme Models.- 6.4 Use of Whole Cell Systems.- 6.4.1 Principles.- 6.4.2 Application to Unnatural Substrates.- 6.5 Application of Biocatalytic Hydrolysis.- 6.5.1 General Remarks.- 6.5.2 Resolution of Racemates.- 6.5.3 Asymmetrization of Prochiral and meso-Compounds.- 6.5.4 Selective Protection and Deprotection.- 6.5.5 Mild Conditions.- 6.6 Reduction and Oxidation Using Biocatalysts.- 6.6.1 Introduction.- 6.6.2 Enzymatic Cofactor Recycling.- 6.6.3 Enantioface Differentiation in Reduction of Ketones.- 6.6.4 Oxidation of Ketones.- 6.6.5 Hydroxylation of Nonactivated Carbon Atoms.- 6.6.6 Other Oxidations.- 6.7 Further Applications.- 6.7.1 Use of Organic Solvents, Transesterification.- 6.7.2 Lyase-Catalyzed Additions to Double Bonds.- 6.7.3 C-C Bond Formation and Cleavage.- 6.7.4 Transferases.- 6.8 Special Techniques and Novel Developments.- 6.8.1 Immobilization Techniques.- 6.8.2 Artificial and Modified Enzymes, Enzyme Mimics.- 6.8.3 Catalytic Antibodies.- 6.9 Comparison of Methods and Outlook.- 6.9.1 Advantages and Disadvantages of Biocatalysts.- 6.9.2 Future Developments and Trends.- 6.10 References.- 7 Preparation of Homochiral Organic Compounds.- 7.1 Introduction.- 7.2 Separation Techniques.- 7.3 Homochiral Building Blocks from Natural Products.- 7.4 Auxiliary Modified Substrates.- 7.5 Homochiral Reagents.- 7.6 Homochiral Catalysts.- 7.7 References.- 8 Transition Metal Chemistry and Optical Activity - Werner-Type Complexes, Organometallic Compounds, Enantioselective Catalysis.- 8.1 Werner-Type Complexes.- 8.2 Organometallic Compounds.- 8.3 Enantioselective Catalysis with Optically Active Transition Compounds.- 8.4 References.- 9 Strategies for Liquid Chromatographic Resolution of Enantiomers.- 9.1 Background of Basic Chromatorgraphic Terms.- 9.2 Strategies to Separate Enantiomers by Chromatographic Techniques.- 9.3 Thermodynamic and Kinetic Considerations for Chromatographic Enantioseparation.- 9.4 Enantioselective Liquid Chromatography.- 9.5 Direct Enantioseparation by Liquid Chromatography.- 9.6 Chiral Phases Using Polymers as Chiral Selectors.- 9.7 Chiral Stationary Phases Using Proteins (Polypeptides) as Chiral Selectors.- 9.8 Chiral Stationary Phases Based on Synthetic Chiral Polymers.- 9.9 Chiral Stationary Phases Based on "Brush Type" Immobilization of Small Selector Molecules.- 9.10 Final Remarks on Brush Type and Inclusion Type CSPs.- 9.11 Indirect Enantioseparation.- 9.12 Final Remarks.- 9.13 References.- 10 The Nucleoproteinic System.- 10.1 Introduction.- 10.2 The Chiral Message.- 10.3 The Evolution of the Chiral Amphiphilic Patterns.- 10.3.1 Darwinian Selection for Chiral Information-Processing Patterns.- 10.3.2 Basal Geometries of Chiral Nucleoproteinic Constituents.- 10.3.3 The DNA-RNA-Protein Triad.- 10.4 Stabilization Within the Dynamics.- 10.5 Outlook.- 10.6 References.
13 citations
TL;DR: Ab initio estimations including the chiral electroweak force indicate that the L-amino acids and the D-sugars are more stable than the corresponding enantiomers, which account for the choice of biomolecular handedness made when life began.
12 citations
01 Jan 1991
TL;DR: Ab initio estimations including the chiral electroweak force indicate that the L-amino acids and the D-sugars are more stable than the corresponding enantiomers, which account for the choice of biomolecular handedness made when life began.
Abstract: Pasteur (1860) showed that many organic molecules form enantiomeric pairs with non-superposable mirror-image shapes, characterized by their oppositely signed optical rotation but otherwise apparently identical. Equal numbers of left-handed and right-handed molecules resulted from laboratory synthesis, whereas biosynthetic processes afforded only one of the two enantiomers, leading Pasteur to conclude that biosynthesis involves a chiral force. Fischer demonstrated (1890-1919) that functional biomolecules are composed specifically of the D-sugars and the L-amino acids and that the laboratory synthetic reactions of such molecules propagate with chiral stereoselectivity. Given a primordial enantiomer, biomolecular homochirality follows without the intervention of a chiral natural force, except prebiotically. Chiral forces known at the time were found to be even handed on a time and space average, exemplifying parity conservation (1927). The weak nuclear force, shown to violate parity (1956), was unified with electro-magnetism in the electroweak force (1970). Ab initio estimations including the chiral electroweak force indicate that the L-amino acids and the D-sugars are more stable than the corresponding enantiomers. The small energy difference between these enantiomeric pairs, with Darwinian reaction kinetics in a flow reactor, account for the choice of biomolecular handedness made when life began.
11 citations