Physical Sciences

Search by keywords:
Total Articles 73 - 81 of 173 | |

A Necessary Condition for Coexistence of Autocatalytic Replicators in a Prebiotic Environment

Author(s):Andres F. Hernandez -- Martha A. Grover
Journal: Life
Publisher:
Abstract
| Pages: 403-420
A necessary, but not sufficient, mathematical condition for the coexistence of short replicating species is presented here. The mathematical condition is obtained for a prebiotic environment, simulated as a fed-batch reactor, which combines monomer recycling, variable reaction order and a fixed monomer inlet flow with two replicator types and two monomer types. An extensive exploration of the parameter space in the model validates the robustness and efficiency of the mathematical condition, with nearly 1.7% of parameter sets meeting the condition and half of those exhibiting sustained coexistence. The results show that it is possible to generate a condition of coexistence, where two replicators sustain a linear growth simultaneously for a wide variety of chemistries, under an appropriate environment. The presence of multiple monomer types is critical to sustaining the coexistence of multiple replicator types.

Simple Organics and Biomonomers Identified in HCN Polymers: An Overview

Author(s):Marta Ruiz-Bermejo -- María-Paz Zorzano -- Susana Osuna-Esteban
Journal: Life
Publisher:
Abstract
| Pages: 421-448
Hydrogen cyanide (HCN) is a ubiquitous molecule in the Universe. It is a compound that is easily produced in significant yields in prebiotic simulation experiments using a reducing atmosphere. HCN can spontaneously polymerise under a wide set of experimental conditions. It has even been proposed that HCN polymers could be present in objects such as asteroids, moons, planets and, in particular, comets. Moreover, it has been suggested that these polymers could play an important role in the origin of life. In this review, the simple organics and biomonomers that have been detected in HCN polymers, the analytical techniques and procedures that have been used to detect and characterise these molecules and an exhaustive classification of the experimental/environmental conditions that favour the formation of HCN polymers are summarised. Nucleobases, amino acids, carboxylic acids, cofactor derivatives and other compounds have been identified in HCN polymers. The great molecular diversity found in HCN polymers encourages their placement at the central core of a plausible protobiological system.

Stability toward High Energy Radiation of Non-Proteinogenic Amino Acids: Implications for the Origins of Life

Author(s):Franco Cataldo -- Susana Iglesias-Groth -- Giancarlo Angelini -- Yaser Hafez
Journal: Life
Publisher:
Abstract
| Pages: 449-473
A series of non-proteinogenic amino acids, most of them found quite commonly in the meteorites known as carbonaceous chondrites, were subjected to solid state radiolysis in vacuum to a total radiation dose of 3.2 MGy corresponding to 23% of the total dose expected to be taken by organic molecules buried in asteroids and meteorites since the beginning of the solar system 4.6 × 109 years ago. The radiolyzed amino acids were studied by FT-IR spectroscopy, Differential Scanning Calorimetry (DSC) and by polarimety and Optical Rotatory Dispersion (ORD). It is shown that an important fraction of each amino acid is able to “survive” the massive dose of radiation, while the enantiomeric excess is partially preserved. Based on the results obtained, it is concluded that it is unsurprising to find amino acids even in enantiomeric excess in carbonaceous chondrites.

Model of Biological Quantum Logic in DNA

Author(s):F. Matthew Mihelic
Journal: Life
Publisher:
Abstract
| Pages: 474-481
The DNA molecule has properties that allow it to act as a quantum logic processor. It has been demonstrated that there is coherent conduction of electrons longitudinally along the DNA molecule through pi stacking interactions of the aromatic nucleotide bases, and it has also been demonstrated that electrons moving longitudinally along the DNA molecule are subject to a very efficient electron spin filtering effect as the helicity of the DNA molecule interacts with the spin of the electron. This means that, in DNA, electrons are coherently conducted along a very efficient spin filter. Coherent electron spin is held in a logically and thermodynamically reversible chiral symmetry between the C2-endo and C3-endo enantiomers of the deoxyribose moiety in each nucleotide, which enables each nucleotide to function as a quantum gate. The symmetry break that provides for quantum decision in the system is determined by the spin direction of an electron that has an orbital angular momentum that is sufficient to overcome the energy barrier of the double well potential separating the C2-endo and C3-endo enantiomers, and that enantiomeric energy barrier is appropriate to the Landauer limit of the energy necessary to randomize one bit of information.

Extremophiles and Extreme Environments

Author(s):Pabulo Henrique Rampelotto
Journal: Life
Publisher:
Abstract
| Pages: 482-485
Over the last decades, the study of extremophiles has providing ground breaking discoveries that challenge the paradigms of modern biology and make us rethink intriguing questions such as "what is life?", "what are the limits of life?", and "what are the fundamental features of life?". These findings and possibilities have made the study of life in extreme environments one of the most exciting areas of research in recent decades. However, despite the latest advances we are just in the beginning of exploring and characterizing the world of extremophiles. This special issue discusses several aspects of these fascinating organisms, exploring their habitats, biodiversity, ecology, evolution, genetics, biochemistry, and biotechnological applications in a collection of exciting reviews and original articles written by leading experts and research groups in the field. [...]

Formaldehyde—A Key Monad of the Biomolecular System

Author(s):Christian R. Noe -- Jerome Freissmuth -- Peter Richter -- Christian Miculka -- Bodo Lachmann -- Simon Eppacher
Journal: Life
Publisher:
Abstract
| Pages: 486-501
Experiments will be presented and reviewed to support the hypothesis that the intrinsic reactivity of formaldehyde may lead to the formation of a rather comprehensive set of defined biomolecules, including D-glucose, thus fostering concepts of evolution considering the existence of a premetabolic system as a primordial step in the generation of life.

Natural Pyrrhotite as a Catalyst in Prebiotic Chemical Evolution

Author(s):Alejandra López Ibáñez de Aldecoa -- Francisco Velasco Roldán -- César Menor-Salván
Journal: Life
Publisher:
Abstract
| Pages: 502-517
The idea of an autotrophic organism as the first living being on Earth leads to the hypothesis of a protometabolic, complex chemical system. In one of the main hypotheses, the first metabolic systems emerged from the interaction between sulfide minerals and/or soluble iron-sulfide complexes and fluids rich in inorganic precursors, which are reduced and derived from crustal or mantle activity. Within this context, the possible catalytic role of pyrrhotite, one of the most abundant sulfide minerals, in biomimetic redox and carbon fixation reactions was studied. Our results showed that pyrrhotite, under simulated hydrothermal conditions, could catalyze the pyruvate synthesis from lactate and that a dynamic system formed by coupling iron metal and iron-sulfur species in an electrochemical cell could promote carbon fixation from thioacetate esters.

Horizontal Gene Transfer and Its Part in the Reorganisation of Genetics during the LUCA Epoch

Author(s):Sohan Jheeta
Journal: Life
Publisher:
Abstract
| Pages: 518-523
Currently there are five known mechanisms of horizontal gene transfer (HGT): transduction, conjugation, transformation, gene transfer agents and membrane vesicle transfer. The question here is: what part did HGT play in the reorganisation of genetics during the last universal common ancestor (LUCA) epoch? LUCA is a construct to explain the origin of the three domains of life; namely Archaea, Bacteria and Eukarya. This editorial offers a general introduction to the relevance and ultimate significance of HGT in relation to the LUCA. [...]

Distance and Size Perception in Astronauts during Long-Duration Spaceflight

Author(s):Gilles Clément -- Anna Skinner -- Corinna Lathan
Journal: Life
Publisher:
Abstract
| Pages: 524-537
 Exposure to microgravity during spaceflight is known to elicit orientation illusions, errors in sensory localization, postural imbalance, changes in vestibulo-spinal and vestibulo-ocular reflexes, and space motion sickness. The objective of this experiment was to investigate whether an alteration in cognitive visual-spatial processing, such as the perception of distance and size of objects, is also taking place during prolonged exposure to microgravity. Our results show that astronauts on board the International Space Station exhibit biases in the perception of their environment. Objects’ heights and depths were perceived as taller and shallower, respectively, and distances were generally underestimated in orbit compared to Earth. These changes may occur because the perspective cues for depth are less salient in microgravity or the eye-height scaling of size is different when an observer is not standing on the ground. This finding has operational implications for human space exploration missions.
Page:12345678910Next