chirality Archives

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Imaging & Spectroscopy, Status Report

Analysis of Chiral Oxirane Molecules in Preparation for Next Generation Telescopes: A Review, New Analysis, & a Chiral Molecule Database

by Keith CowingNovember 29, 2023November 29, 2023

Human biology has a preference for left-handed chiral molecules and an outstanding question is if this is imposed through astrophysical origins.

Chiral molecules can spin polarize magnetic surfaces due to the CISS effect. A. Electron density of a molecule approaching a surface is asymmetrically distributed and a transient charge dipole is created. Charge transport through chiral molecules is spin selective due to the CISS effect and therefore a spin-dipole along the chiral molecular axis accompanies this charge dipole. This transient spin dipole can couple with surface spins due to the spin-exchange interaction (J ≡ [E(↑↑) − E(↑↓)]) and spin polarize the surface along the chiral molecular axis. B. Schematic of the setup used in crystallization experiments for CD detection. Homochiral crystals of RAO are formed on magnetite from their enantiopure solution. These crystals align the magnetic domains under them and interact with the surface spins due to magnetic dipolar coupling—a weaker but longer range coupling compared to the spin-exchange interaction C. A sequence showing the effect of chiral molecules on the magnetic domains. 1 Initially, there is no net magnetization of the magnetic domains. 2 As a layer of RAO is forming, the spins underneath the layer align due to the strong spin-exchange interaction. This is an avalanche magnetization process: molecules align the surface spins and the aligned regions attract more molecules and get larger. 3 The mono-layer grows and covers more surface due to the attraction of chiral molecules to the aligned regions and crystal seeds start forming. 4 Crystals get larger and couple with the magnetic domains due to magnetic dipole-dipole interaction, Edd. D. If an external magnetic field, −→B, is applied, the domains outside the area covered by crystals magnetize. Yet the crystals preserve the magnetization of the domains under them as long as the energy of the dipolar coupling is larger than the magnetic energy. -- physics.chem-ph

Astrochemistry, Biochemistry & Organic Chemistry, Biophysics, Genomics, Proteomics, Bioinformatics, Origin & Evolution of Life, Press Release

Chirality-Induced Magnetization of Magnetite by an RNA Precursor

by Keith CowingJune 18, 2023June 16, 2023

Life is homochiral and homochirality is a fundamental feature of living systems on Earth. While the exact mechanism that led to homochirality is still not fully understood, any realistic scenario […]

Propagation of homochirality from a common ribonucleotide precursor, RAO, to the entire prebiotic network is illustrated. D-RAO can be transformed into D-ribonucleotides, forming homochiral RNA. L-peptides can be synthesized through the stereoselective binding of L-amino acids to tRNA analogs composed of D-ribonucleotides. This crucial link enables the transfer of homochirality from nucleic acids to peptides. Then L-peptides form L-enzymes, and by enantioselective catalysis a homochiral metabolism can be produced. -- physics.chem-ph

Biochemistry & Organic Chemistry, Genomics, Proteomics, Bioinformatics, Origin & Evolution of Life, Status Report

The Central Dogma Of Biological Homochirality: How Does Chiral Information Propagate In A Prebiotic Network?

by Keith CowingJune 14, 2023June 14, 2023

Biological systems are homochiral, raising the question of how a racemic mixture of prebiotically synthesized biomolecules could attain a homochiral state at the network level.

High enantiomeric excesses (ee’s) of l-amino acids, including non-proteinogenic amino acid isovaline (Iva), were discovered in the Murchison meteorite, but the detailed molecular mechanism responsible for the observed ee of amino acids remains elusive and inconsistent, because Iva has an inverted circular dichroism (CD) spectrum with respect to α-H amino acids, e.g., alanine. To address this issue, we resort to accurate ab initio calculations for amino acids and their precursors in the Strecker synthesis. We evaluated their photolysis-induced ee in the range 5–11 eV including the Lyman alpha emission line (Lyα), the typical intensive 10.2 eV radiation ascribed to the early phase of galactic evolution. We show that only the aminonitrile precursors are characterized by positive ee in the Lyα region, explaining why right-handed circularly polarized Lyα (R-CP-Lyα) induces homologous l-amino acids. This study shows that the homochirality of amino acids is produced at the aminonitrile precursors stage.-- The Journal of Physical Chemistry Letters

Astrochemistry, Biochemistry & Organic Chemistry, Meteorites & Asteroids, Press Release

New Study Provides Novel Insights Into The Cosmic Evolution Of Amino Acids

by Keith CowingMay 26, 2023

All biological amino acids on Earth appear exclusively in their left-handed form, but the reason underlying this observation is elusive.

Biochemistry & Organic Chemistry, Genomics, Proteomics, Bioinformatics, Origin & Evolution of Life, Press Release

Solving The Mystery Of Left-handed Amino Acids In Primordial RNA Reactions

by Keith CowingMarch 17, 2023March 17, 2023

While humans have an esthetic liking for symmetry in everything, nature prefers asymmetric, single-handed forms when it comes to amino acids—the building blocks of proteins, and, by extension, all things […]

Astrochemistry

The Chiral Puzzle Of Life

by Keith CowingJuly 11, 2022

Biological molecules chose one of two structurally, chiral systems which are related by reflection in a mirror. It is proposed that this choice was made, causally, by magnetically polarized and […]

Astrogeology, Atmospheres, Climate, Weather, Press Release, Water/Hycean Worlds & Oceanography

Study Hints that Ancient Earth Made Its Own Water Geologically

by Keith CowingDecember 17, 2014

A new study is helping to answer a longstanding question that has recently moved to the forefront of earth science: Did our planet make its own water through geologic processes, […]

Astrochemistry, Press Release

Cosmic Explanation for Life's 'Left-Handed' Amino Acids

by Keith CowingApril 23, 2013

A research team with Jungmi Kwon (GUAS/NAOJ) has performed deep imaging linear and circular polarimetry (Note 1) of the ‘Cat’s Paw Nebula’ (NGC 6334) (Note 2) located in the constellation […]