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1.
Stanley I. Goldberg 《Origins of life and evolution of the biosphere》2007,37(1):55-60
Evaporation of an aqueous solution of a chiral, nonracemic (partially resolved) amino acid or hydroxy acid from a clay or
silica surface is shown to produce crystals in six cases that possess increased concentrations of the more abundant enantiomer.The
increases range from a factor of 1.2 as the low to a high greater than 6-fold above the near 8% enantiomeric excess starting
levels. This newly discovered enantiomeric enrichment process is presented in the context of it having been a possible instrument
in the attainment of levels of configurational homogeneity sufficient for the emergence of life on Earth.
Portions of this work were presented to The 14th International Conference on the Origin of Life, Beijing, China, June 21,
2005 相似文献
2.
Ronald Breslow Mindy Levine Zhan-Ling Cheng 《Origins of life and evolution of the biosphere》2010,40(1):11-26
We show how the amino acids needed on prebiotic earth in their homochiral L form can be produced by a reaction of L-alpha-methyl
amino acids—that have been identified in the Murchison meteorite—with alpha-keto acids under credible prebiotic conditions.
When they are simply heated together they perform a process of decarboxylative transamination but with almost no chiral transfer,
and that in the wrong direction, producing D-amino acids from the L-alpha-methyl amino acids. With copper ion a square planar
complex with two of the reaction intermediates is formed, and now there is the desired L to L transformation, producing small
enantioexcesses of the normal L-amino acids. We also show how these can be amplified, not by making more of the L form but
by increasing its concentration in water solution. The process can start with a miniscule excess and in one step generate
water solutions with L/D ratios in the over 90% region. Kinetic processes can exceed the results from equilibria. We have
also examined such amplifications with ribonucleosides, and have shown that initial modest excesses of the D-nucleosides can
be amplified to afford water solutions with D to L ratios in the high 90’s. We have shown that the homochiral compound has
two effects on the solubility of the racemate. On one hand it decreases the solubility of the racemate by its role in the
solubility product, as a theoretical equation predicts. On the other hand, it increases the solubility of the racemate by
changing the nature of the solvent, acting as a cosolvent with the water. This explains why the amplification, while large,
is not as large as the simple theoretical equation predicts. Thus when credible examples are produced where small enantioexcesses
of D-ribose are created under credible prebiotic conditions, the prerequisites for the RNA world will have been exemplified. 相似文献
3.
Lunine JI 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2006,361(1474):1721-1731
The formation of the Earth as a planet was a large stochastic process in which the rapid assembly of asteroidal-to-Mars-sized bodies was followed by a more extended period of growth through collisions of these objects, facilitated by the gravitational perturbations associated with Jupiter. The Earth's inventory of water and organic molecules may have come from diverse sources, not more than 10% roughly from comets, the rest from asteroidal precursors to chondritic bodies and possibly objects near Earth's orbit for which no representative class of meteorites exists today in laboratory collections. The final assembly of the Earth included a catastrophic impact with a Mars-sized body, ejecting mantle and crustal material to form the Moon, and also devolatilizing part of the Earth. A magma ocean and steam atmosphere (possibly with silica vapour) existed briefly in this period, but terrestrial surface waters were below the critical point within 100 million years after Earth's formation, and liquid water existed continuously on the surface within a few hundred million years. Organic material delivered by comets and asteroids would have survived, in part, this violent early period, but frequent impacts of remaining debris probably prevented the continuous habitability of the Earth for one to several hundred million years. Planetary analogues to or records of this early time when life began include Io (heat flow), Titan (organic chemistry) and Venus (remnant early granites). 相似文献
4.
Atmospheric composition and climate on the early Earth 总被引:4,自引:0,他引:4
Kasting JF Howard MT 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2006,361(1474):1733-41; discussion 1741-2
Oxygen isotope data from ancient sedimentary rocks appear to suggest that the early Earth was significantly warmer than today, with estimates of surface temperatures between 45 and 85 degrees C. We argue, following others, that this interpretation is incorrect-the same data can be explained via a change in isotopic composition of seawater with time. These changes in the isotopic composition could result from an increase in mean depth of the mid-ocean ridges caused by a decrease in geothermal heat flow with time. All this implies that the early Earth was warm, not hot.A more temperate early Earth is also easier to reconcile with the long-term glacial record. However, what triggered these early glaciations is still under debate. The Paleoproterozoic glaciations at approximately 2.4Ga were probably caused by the rise of atmospheric O2 and a concomitant decrease in greenhouse warming by CH4. Glaciation might have occurred in the Mid-Archaean as well, at approximately 2.9Ga, perhaps as a consequence of anti-greenhouse cooling by hydrocarbon haze. Both glaciations are linked to decreases in the magnitude of mass-independent sulphur isotope fractionation in ancient rocks. Studying both the oxygen and sulphur isotopic records has thus proved useful in probing the composition of the early atmosphere. 相似文献
5.
The Reactions of Methanimine and Cyanogen with Carbon Monoxide in Prebiotic Molecular Evolution on Earth 总被引:2,自引:0,他引:2
A primeval atmosphere is proposedcontaining simple molecules such as formaldehyde, ammonia, carbon monoxide, cyanogen andhydrogen cyanide, which have been detected in space. Chemical reactions aredescribed for the formation ofaziridine-2-one and di-azirine-3-one derivatives aspotential precursors for the original synthesesis of amino-acids, proteins, pyrimidines,purines, nicotinamide and flavin. The reactions have been shown to be kinetically feasiblefrom the overall enthalpy changes in the ZKE approximation at the MP2/6-31G* level. 相似文献
6.
Daniele Dondi Daniele Merli Luca Pretali Maurizio Fagnoni Angelo Albini Nick Serpone 《Photochemical & photobiological sciences》2007,6(11):1210-1217
A series of prebiotic mixtures of simple molecules, sources of C, H, N, and O, were examined under conditions that may have prevailed during the Hadean eon (4.6-3.8 billion years), namely an oxygen-free atmosphere and a significant UV radiation flux over a large wavelength range due to the absence of an ozone layer. Mixtures contained a C source (methanol, acetone or other ketones), a N source (ammonia or methylamine), and an O source (water) at various molar ratios of C : H : N : O. When subjected to UV light or heated for periods of 7 to 45 days under an argon atmosphere, they yielded a narrow product distribution of a few principal compounds. Different initial conditions produced different distributions. The nature of the products was ascertained by gas chromatographic-mass spectral analysis (GC-MS). UVC irradiation of an aqueous methanol-ammonia-water prebiotic mixture for 14 days under low UV dose (6 x 10(-2) Einstein) produced methylisourea, hexamethylenetetramine (HMT), methyl-HMT and hydroxy-HMT, whereas under high UV dose (45 days; 1.9 x 10(-1) Einstein) yielded only HMT. By contrast, the prebiotic mixture composed of acetone-ammonia-water produced five principal species with acetamide as the major component; thermally the same mixture produced a different product distribution of four principal species. UVC irradiation of the CH(3)CN-NH(3)-H(2)O prebiotic mixture for 7 days gave mostly trimethyl-s-triazine, whereas in the presence of two metal oxides (TiO(2) or Fe(2)O(3)) also produced some HMT; the thermal process yielded only acetamide. 相似文献
7.
With growing evidence for a heavy bombardment period ending 4–3.8 billion years ago, meteorites and comets may have been an
important source of prebiotic carbon, nitrogen, and phosphorus on the early Earth. Life may have originated shortly after
the late-heavy bombardment, when concentrations of organic compounds and reactive phosphorus were enough to “kick life into
gear”. This work quantifies the sources of potentially prebiotic, extraterrestrial C, N, and P and correlates these fluxes
with a comparison to total Ir fluxes, and estimates the effect of atmosphere on the survival of material. We find (1) that
carbonaceous chondrites were not a good source of organic compounds, but interplanetary dust particles provided a constant,
steady flux of organic compounds to the surface of the Earth, (2) extraterrestrial metallic material was much more abundant
on the early Earth, and delivered reactive P in the form of phosphide minerals to the Earth’s surface, and (3) large impacts
provided substantial local enrichments of potentially prebiotic reagents. These results help elucidate the potential role
of extraterrestrial matter in the origin of life. 相似文献
8.
Functional Superoxide Dismutase Mimics Become Diverse: From Simple Compounds on Prebiotic Earth to Nanozymes 总被引:1,自引:0,他引:1
Inorganic solids with enzyme-like activity are promising to overcome many restrictions of native enzymes in application.Especially attractive are nanoparticles with superoxide dismutase(SOD)activity,due to their ability to reduce the damaging properties of reactive oxygen species within cells and organism.This review discusses the necessary requirements for nanoparticles to have SOD activity and reveals a close relationship between catalysis on prebiotic earth and the recent SOD mimics.This review also aims to highlight the progress in the development of SOD mimicking nanoparticles.We give a broad overview of nanoparticles with SOD activity,based on their material make-up,to underline their increasing diversity. 相似文献
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10.
A. Yu. Rozanov 《Paleontological Journal》2010,44(7):839-850
The organization level of Precambrian fossils is the most reliable indicator of the state and parameters of the biosphere,
such as the atmosphere composition, average temperature of the earth’s surface, and others. At present, cyanobacteria, unicellular
and multicellular eukaryotes, and coelomates are considered to appear in the geological history of the Earth much earlier
than it was supposed previously. Our knowledge and ideas of the early Earth are very important for considering the problems
of the origin of life. A key boundary of the earliest period was probably about 4 Ga. This boundary is between the periods
documented and undocumented by the geological record. The Earth history and probable surface conditions before 4 Ga are considered
by L.M. Mukhina, A.V. Vityazeva, G.V. Pechernikova, and L.V. Ksanfomaliti in this volume. 相似文献
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12.
First off the mark: early seed germination 总被引:4,自引:0,他引:4
13.
Sugar-Driven Prebiotic Synthesis of Ammonia from Nitrite 总被引:1,自引:0,他引:1
Arthur L. Weber 《Origins of life and evolution of the biosphere》2010,40(3):245-252
Reaction of 3–5 carbon sugars, glycolaldehyde, and α-ketoaldehydes with nitrite under mild anaerobic aqueous conditions yielded
ammonia, an essential substrate for the synthesis of nitrogen-containing molecules during abiogenesis. Under the same conditions,
ammonia synthesis was not driven by formaldehyde, glyoxylate, 2-deoxyribose, and glucose, a result indicating that the reduction
process requires an organic reductant containing either an accessible α-hydroxycarbonyl group or an α-dicarbonyl group. Small
amounts of aqueous Fe+3 catalyzed the sugar-driven synthesis of ammonia. The glyceraldehyde concentration dependence of ammonia synthesis, and control
studies of ammonia’s reaction with glyceraldehyde, indicated that ammonia formation is accompanied by incorporation of part
of the synthesized ammonia into sugar-derived organic products. The ability of sugars to drive the synthesis of ammonia is
considered important to abiogenesis because it provides a way to generate photochemically unstable ammonia at sites of sugar-based
origin-of-life processes from nitrite, a plausible prebiotic nitrogen species. 相似文献
14.
Coenzymes are essential across all domains of life. B vitamins (B1‐thiamin, B2‐riboflavin, B3‐niacin, B5‐pantothenate, B6‐pyridoxine, B7‐biotin, and B12‐cobalamin) represent the largest class of coenzymes, which participate in a diverse set of reactions including C1‐rearrangements, DNA repair, electron transfer, and fatty acid synthesis. B vitamin structures range from simple to complex heterocycles, yet, despite this complexity, multiple lines of evidence exist for their ancient origins including abiotic synthesis under putative early Earth conditions and/or meteorite transport. Thus, some of these critical coenzymes likely preceded life on Earth. Some modern organisms can synthesize their own B vitamins de novo while others must either scavenge them from the environment or establish a symbiotic relationship with a B vitamin producer. B vitamin requirements are widespread in some of the most ancient metabolisms including all six carbon fixation pathways, sulfate reduction, sulfur disproportionation, methanogenesis, acetogenesis, and photosynthesis. Understanding modern metabolic B vitamin requirements is critical for understanding the evolutionary conditions of ancient metabolisms as well as the biogeochemical cycling of critical elements such as S, C, and O. 相似文献
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16.
Prebiotic effectiveness of inulin extracted from edible burdock 总被引:1,自引:0,他引:1
To investigate the prebiotic potential of burdock inulin (B-INU), the in vitro and in vivo effects of B-INU on bacterial growth were studied. B-INU significantly stimulated the growth of bifidobacteria in Man-Rogosa-Sharp (MRS) medium, anaerobically. Compared with chicory inulin (C-INU), long-chain inulin (L-INU) and fructooligosaccharides (FOS), 1% (w/v) B-INU promoted the specific growth rate of beneficial bacteria. The decreases of media pH with B-INU were almost the same as that with C-INU and FOS. In vivo, B-INU significantly increased the number of lactobacilli and bifidobacteria (P<0.05) in cecal content. Mice fed with B-INU, C-INU and FOS for 14 days had greater number of cecal beneficial bacteria population than those fed with L-INU for 14 days. In addition, all fructans did not cause any side effects, such as eructation and bloating. Results indicated that inulin extracted from edible burdock showed prebiotic properties that could promote health. 相似文献
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Eric T. Parker H. James Cleaves Michael P. Callahan Jason P. Dworkin Daniel P. Glavin Antonio Lazcano Jeffrey L. Bada 《Origins of life and evolution of the biosphere》2011,41(3):201-212
Original extracts from an unpublished 1958 experiment conducted by the late Stanley L. Miller were recently found and analyzed
using modern state-of-the-art analytical methods. The extracts were produced by the action of an electric discharge on a mixture
of methane (CH4), hydrogen sulfide (H2S), ammonia (NH3), and carbon dioxide (CO2). Racemic methionine was formed in significant yields, together with other sulfur-bearing organic compounds. The formation
of methionine and other compounds from a model prebiotic atmosphere that contained H2S suggests that this type of synthesis is robust under reducing conditions, which may have existed either in the global primitive
atmosphere or in localized volcanic environments on the early Earth. The presence of a wide array of sulfur-containing organic
compounds produced by the decomposition of methionine and cysteine indicates that in addition to abiotic synthetic processes,
degradation of organic compounds on the primordial Earth could have been important in diversifying the inventory of molecules
of biochemical significance not readily formed from other abiotic reactions, or derived from extraterrestrial delivery. 相似文献