scholarly journals Geochemical influences on nonenzymatic oligomerization of prebiotically relevant cyclic nucleotides

2019 ◽  
Author(s):  
Shikha Dagar ◽  
Susovan Sarkar ◽  
Sudha Rajamani
Keyword(s):  
Cyclic Nucleotides ◽  
Hot Spring ◽  
Rna World ◽  
Early Earth ◽  
Pyrimidine Nucleotides ◽  
Diurnal Cycles ◽  
Alkaline Conditions ◽  
Purine And Pyrimidine Nucleotides ◽  
The Stability ◽  
Emergence Of Life

AbstractThe spontaneous emergence of RNA on the early Earth continues to remain an enigma in the field of origins of life. Few studies have looked at the nonenzymatic oligomerization of cyclic nucleotides under neutral to alkaline conditions, in fully dehydrated state. Herein, we systematically investigated the oligomerization of cyclic nucleotides under prebiotically relevant conditions, where starting reactants were subjected to repeated dehydration-rehydration (DH-RH) regimes, like they would have been on an early Earth. DH-RH conditions, a recurring geological theme, are driven by naturally occurring processes including diurnal cycles and tidal pool activity. These conditions have been shown to facilitate uphill oligomerization reactions in terrestrial geothermal niches, which are hypothesized to be pertinent sites for the emergence of life. 2′-3′ and 3′-5′ cyclic nucleotides of one purine-based (adenosine) and one pyrimidine-based (cytidine) system were evaluated in this study. Additionally, the effect of amphiphiles was also investigated. Furthermore, to discern the effect of ‘realistic’ conditions on this process, the reactions were also performed using hot spring water samples from an early Earth analogue environment. Our results showed that the oligomerization of cyclic nucleotides under DH-RH conditions resulted in intact informational oligomers. Amphiphiles increased the stability of, both, the starting monomers and the resultant oligomers. In analogue condition reactions, oligomerization of nucleotides and back-hydrolysis of the resultant oligomers was pronounced. Altogether, this study demonstrates how nonenzymatic oligomerization of cyclic purine and pyrimidine nucleotides, under laboratory-simulated and early Earth analogous conditions, could have resulted in RNA oligomers of a putative RNA World.

A Venus-like atmosphere on the early Earth from magma ocean outgassing

2020 ◽  
Author(s):  
Paolo Sossi ◽  
Antony Burnham ◽  
James Badro ◽  
Antonio Lanzirotti ◽  
Matt Newville ◽  
...  
Keyword(s):  
Dominant Role ◽  
Mantle Peridotite ◽  
Early Earth ◽  
Magma Ocean ◽  
Gaseous Species ◽  
The Earth ◽  
Prebiotic Atmosphere ◽  
The Stability ◽  
The Relationship ◽  
Emergence Of Life

<p>Outgassing of an early magma ocean on Earth plays a dominant role in determining the composition of its secondary atmosphere, and hence bears on the potential for the emergence of life. The stability of gaseous species in such an atmosphere reflects the redox state of the magma ocean. However, the relationship between oxygen fugacity (fO<sub>2</sub>) and the oxidation state of the most abundant polyvalent element, Fe, in likely magma ocean compositions is poorly constrained. Here we determine Fe<sup>2+</sup>/Fe<sup>3+</sup> ratios as a function of fO<sub>2</sub> in peridotite liquids, experimentally synthesised by aerodynamic laser levitation at 1 bar and 2173 K. We show that a magma ocean with Fe<sup>3+</sup>/∑Fe akin to that of contemporary upper mantle peridotite (0.037) would have had fO<sub>2</sub> 0.5 log units higher than the Fe-“FeO” equilibrium. At this relative fO<sub>2</sub>, a neutral CO<sub>2</sub>-H<sub>2</sub>O-dominated atmosphere of ~ 150 bar would have developed on the early Earth, taking into account the solubilities of the major volatiles, H, C, N and O in the magma ocean. Upon cooling, the Earth’s prebiotic atmosphere was likely comprised of CO<sub>2</sub>-N<sub>2</sub>, in proportions and at pressures akin to that on presently found on Venus.</p>

A review of lignin hydrogen peroxide oxidation chemistry with emphasis on aromatic aldehydes and acids

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ajinkya More ◽  
Thomas Elder ◽  
Zhihua Jiang
Keyword(s):  
Hydrogen Peroxide ◽  
Oxidative Degradation ◽  
Reaction Medium ◽  
Dicarboxylic Acids ◽  
Aromatic Aldehydes ◽  
Product Distribution ◽  
Reaction Conditions ◽  
Alkaline Conditions ◽  
The Stability ◽  
Oxidation Chemistry

Abstract This review discusses the main factors that govern the oxidation processes of lignins into aromatic aldehydes and acids using hydrogen peroxide. Aromatic aldehydes and acids are produced in the oxidative degradation of lignin whereas mono and dicarboxylic acids are the main products. The stability of hydrogen peroxide under the reaction conditions is an important factor that needs to be addressed for selectively improving the yield of aromatic aldehydes. Hydrogen peroxide in the presence of heavy metal ions readily decomposes, leading to minor degradation of lignin. This degradation results in quinones which are highly reactive towards peroxide. Under these reaction conditions, the pH of the reaction medium defines the reaction mechanism and the product distribution. Under acidic conditions, hydrogen peroxide reacts electrophilically with electron rich aromatic and olefinic structures at comparatively higher temperatures. In contrast, under alkaline conditions it reacts nucleophilically with electron deficient carbonyl and conjugated carbonyl structures in lignin. The reaction pattern in the oxidation of lignin usually involves cleavage of the aromatic ring, the aliphatic side chain or other linkages which will be discussed in this review.

scholarly journals Synthesis and characterization of one-dimensional titanate structure

2008 ◽  
Vol 2 (2) ◽  
pp. 109-114 ◽  
Author(s):  
Ljubica Nikolic ◽  
Marija Maletin ◽  
Paula Ferreira ◽  
Paula Vilarinho
Keyword(s):  
Heat Treatment ◽  
Structural Characteristics ◽  
Hydrothermal Process ◽  
Synthesis And Characterization ◽  
One Dimensional ◽  
Treatment Conditions ◽  
Alkaline Conditions ◽  
The Stability ◽  
Simple Hydrothermal Process

One-dimensional titania structures were synthesized trough a simple hydrothermal process in a highly alkaline conditions. The aim of this work was to elucidate the effect of time on the formation of 1D titanates as well on its structural characteristics (morphology, phase composition, surface area). Apart from that, the effect of heat treatment conditions on the stability of titanate based 1D samples has been investigated. The results have revealed that it is possible to form one-dimensional titanates already after 1 hour of hydrothermal synthesis. Although the composition of titanates is still under debate, the results probably correspond to the layered sodium titanates. The 1D prepared structures show a remarkable stability during heating, remaining the basic morphology and composition even up to 700?C.

scholarly journals Spectral Characteristic, Storage Stability and Antioxidant Properties of Anthocyanin Extracts from Flowers of Butterfly Pea (Clitoria Ternatea L.)

Molecules ◽  
2021 ◽  
Vol 26 (22) ◽  
pp. 7000
Author(s):  
Xueying Fu ◽  
Qiang Wu ◽  
Jian Wang ◽  
Yanli Chen ◽  
Guopeng Zhu ◽  
...  
Keyword(s):  
Food Processing ◽  
Storage Stability ◽  
Ph Value ◽  
Antioxidant Properties ◽  
Radical Scavenging ◽  
Nutritional Values ◽  
Clitoria Ternatea ◽  
Alkaline Conditions ◽  
Butterfly Pea ◽  
The Stability

Anthocyanins from flowers of the butterfly pea (Clitoria ternatea L.) are promising edible blue food colorants. Food processing often faces extreme pHs and temperatures, which greatly affects the color and nutritional values of anthocyanins. This study explored the color, spectra, storage stability, and antioxidant properties of C. ternatea anthocyanin extract (CTAE) at different pHs. The color and absorption spectra of CTAEs at a pH of 0.5–13 were shown, with their underlying structures analyzed. Then, the storage stability of CTAEs were explored under a combination of pHs and temperatures. The stability of CTAE declines with the increase in temperature, and it can be stored stably for months at 4 °C. CTAEs also bear much resistance to acidic and alkaline conditions but exhibit higher thermal stability at pH 7 (blue) than at pH 0.5 (magenta) or pH 10 (blue-green), which is a great advantage in food making. Antioxidant abilities for flower extracts from the butterfly pea were high at pH 4–7, as assessed by DPPH free radical scavenging assays, and decreased sharply when the pH value exceeded 7. The above results provide a theoretical basis for the application of butterfly pea flowers and imply their great prospect in the food industry.

Heavy Metal Removal in the Presence of Colloid-Stabilizing Organic Material and Complexing Agents

1986 ◽  
Vol 18 (1) ◽  
pp. 19-29 ◽  
Author(s):  
I. Licskó ◽  
I. Takács
Keyword(s):  
Heavy Metals ◽  
Metal Removal ◽  
Heavy Metal Removal ◽  
Colloidal Dispersion ◽  
Laboratory Model ◽  
Complexing Agents ◽  
Stabilizing Agents ◽  
Removal Of Heavy Metals ◽  
Alkaline Conditions ◽  
The Stability

It has been established in laboratory model experiments that the removal of dissolved heavyimetals from wastewaters is rendered more difficult in the presence of colloid-stabilizing agents. This unfavourable effect can be eliminated by the addition of Mg2+ ions and the adjustment to a fairly high pH. By increasing the concentration of Mg2+ ions, the pH necessary for destroying the stability of colloidal dispersion can be lowered. These findings also apply to the combined removal of different heavy metals (Cu, Zn, Cr(III), Ni, Cd). In alkaline conditions, in the presence of ammonium salts, some heavy metals (Cu, Zn, Ni) form high stability amine complexes. A higher pH is necessary for the breakdown of these complexes and the satisfactory removal of heavy metals.

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