scholarly journals Dehydration Enhances Prebiotic Lipid Remodeling and Vesicle Formation in Acidic Environments

2021 ◽  
Author(s):  
Luke H Steller ◽  
Martin J Van Kranendonk ◽  
Anna Wang
Keyword(s):  
Lipid Bilayer ◽  
Building Blocks ◽  
Selective Advantage ◽  
Physicochemical Process ◽  
Vesicle Formation ◽  
Acidic Conditions ◽  
Acidic Environments ◽  
Thin Walled ◽  
Lipid Aggregates

The encapsulation of genetic polymers inside lipid bilayer compartments is a vital step in the emergence of cell-based life. However, even though acidic conditions promote many reactions required for generating prebiotic building blocks, prebiotically-relevant lipids tend to form denser aggregates at acidic pHs rather than prebiotically useful vesicles that exhibit sufficient solute encapsulation. Here we describe how dehydration/rehydration (DR) events, a prebiotically-relevant physicochemical process known to promote polymerization reactions, can remodel dense lipid aggregates into thin-walled vesicles capable of RNA encapsulation even at acidic pHs. Furthermore, DR events appears to favor the encapsulation of RNA within thin-walled vesicles over more lipid-rich vesicles, thus conferring such vesicles a selective advantage.

scholarly journals Lmo0036, an ornithine and putrescine carbamoyltransferase in Listeria monocytogenes, participates in arginine deiminase and agmatine deiminase pathways and mediates acid tolerance

Microbiology ◽  
2011 ◽  
Vol 157 (11) ◽  
pp. 3150-3161 ◽  
Author(s):  
Jianshun Chen ◽  
Changyong Cheng ◽  
Ye Xia ◽  
Hanxin Zhao ◽  
Chun Fang ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Foodborne Pathogens ◽  
Foodborne Pathogen ◽  
Acid Tolerance ◽  
Arginine Deiminase ◽  
Transcriptional Level ◽  
Acidic Conditions ◽  
Acidic Environments ◽  
Agmatine Deiminase

Listeria monocytogenes is a foodborne pathogen causing listeriosis. Acid is one of the stresses that foodborne pathogens encounter most frequently. The ability to survive and proliferate in acidic environments is a prerequisite for infection. However, there is limited knowledge about the molecular basis of adaptation of L. monocytogenes to acid. Arginine deiminase (ADI) and agmatine deiminase (AgDI) systems are implicated in bacterial tolerance to acidic environments. Homologues of ADI and AgDI systems have been found in L. monocytogenes lineages I and II strains. Sequence analysis indicated that lmo0036 encodes a putative carbamoyltransferase containing conserved motifs and residues important for substrate binding. Lmo0036 acted as an ornithine carbamoyltransferase and putrescine carbamoyltransferase, representing the first example, to our knowledge, that catalyses reversible ornithine and putrescine carbamoyltransfer reactions. Catabolic ornithine and putrescine carbamoyltransfer reactions constitute the second step of ADI and AgDI pathways. However, the equilibrium of in vitro carbamoyltransfer reactions was overwhelmingly towards the anabolic direction, suggesting that catabolic carbamoyltransferase was probably the limiting step of the pathways. lmo0036 was induced at the transcriptional level when L. monocytogenes was subjected to low-pH stress. Its expression product in Escherichia coli exhibited higher catabolic carbamoyltransfer activities under acidic conditions. Consistently, absence of this enzyme impaired the growth of Listeria under mild acidic conditions (pH 4.8) and reduced its survival in synthetic human gastric fluid (pH 2.5), and corresponded to a loss in ammonia production, indicating that Lmo0036 was responsible for acid tolerance at both sublethal and lethal pH levels. Furthermore, Lmo0036 played a possible role in Listeria virulence.

Overview and Kinetostatic Characterization of Compliant Shell Mechanism Building Blocks

2020 ◽  
Vol 12 (6) ◽  
Author(s):  
Joep P. A. Nijssen ◽  
Giuseppe Radaelli ◽  
Charles J. Kim ◽  
Just L. Herder
Keyword(s):  
Mechanism Design ◽  
Compliant Mechanism ◽  
Building Blocks ◽  
Concept Design ◽  
Spatial Mechanism ◽  
Thin Walled Structures ◽  
Spatial Geometry ◽  
Thin Walled ◽  
Compliant Mechanism Design

Abstract Compliant shell mechanisms utilize thin-walled structures to achieve motion and force generation. Shell mechanisms, because of their thin-walled nature and spatial geometry, are building blocks for spatial mechanism applications. In spatial compliant mechanism design, the ratio of compliance is the representation of the kinetostatics involved. Using shell mechanisms in concept design, however, can prove difficult without a uniform characterization method. In this article, we make use of compliance ellipsoids to achieve characterization of the ratio of compliance for shell mechanisms. Ten promising shells are presented with the kinetostatic characteristics, combined with a uniform method of determining the kinetostatic characteristics for other unknown shells. Finally, we show how shells are indeed a valid alternative in the spatial mechanism design, compared to conventional flexure mechanisms.

A facile method to fabricate hydrogels from DMSO polymer gels via solvent exchange

2017 ◽  
Vol 41 (12) ◽  
pp. 4793-4796 ◽  
Author(s):  
Heekyoung Choi ◽  
Misun Go ◽  
Yubin Cha ◽  
Yeonweon Choi ◽  
Ki-Young Kwon ◽  
...  
Keyword(s):  
Polymer Gels ◽  
Building Blocks ◽  
Solvent Exchange ◽  
Acidic Conditions

A mixture of the bipyridine, phenyl and/or cyclohexanediamine-based building blocks 1, 2, and/or 3, having hydrazide, aldehyde or amine moieties, respectively, formed DMSO polymer gels by the hydrazone reaction under acidic conditions.

Iridium-catalyzed acid-assisted asymmetric hydrogenation of oximes to hydroxylamines

Science ◽  
2020 ◽  
Vol 368 (6495) ◽  
pp. 1098-1102 ◽  
Author(s):  
Josep Mas-Roselló ◽  
Tomas Smejkal ◽  
Nicolai Cramer
Keyword(s):  
Room Temperature ◽  
Asymmetric Hydrogenation ◽  
Selective Reduction ◽  
Building Blocks ◽  
Efficient Catalyst ◽  
Cyclopentadienyl Ligand ◽  
Acidic Conditions ◽  
Asymmetric Hydrogenations ◽  
Metal Catalyzed ◽  
Oxygen Bond

Asymmetric hydrogenations are among the most practical methods for the synthesis of chiral building blocks at industrial scale. The selective reduction of an oxime to the corresponding chiral hydroxylamine derivative remains a challenging variant because of undesired cleavage of the weak nitrogen-oxygen bond. We report a robust cyclometalated iridium(III) complex bearing a chiral cyclopentadienyl ligand as an efficient catalyst for this reaction operating under highly acidic conditions. Valuable N-alkoxy amines can be accessed at room temperature with nondetected overreduction of the N‒O bond. Catalyst turnover numbers up to 4000 and enantiomeric ratios up to 98:2 are observed. The findings serve as a blueprint for the development of metal-catalyzed enantioselective hydrogenations of challenging substrates.

scholarly journals Escherichia coli Increases its ATP Concentration in Weakly Acidic Environments Principally through the Glycolytic Pathway

Genes ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 991 ◽  
Author(s):  
Wenbin Zhang ◽  
Xin Chen ◽  
Wei Sun ◽  
Tao Nie ◽  
Natalie Quanquin ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Oxidative Phosphorylation ◽  
Metabolic Pathway ◽  
Acid Resistance ◽  
Intestinal Bacteria ◽  
Atp Production ◽  
E Coli ◽  
Major Producer ◽  
Acidic Conditions ◽  
Acidic Environments

Acid resistance is an intrinsic characteristic of intestinal bacteria in order to survive passage through the stomach. Adenosine triphosphate (ATP), the ubiquitous chemical used to power metabolic reactions, activate signaling cascades, and form precursors of nucleic acids, was also found to be associated with the survival of Escherichia coli (E. coli) in acidic environments. The metabolic pathway responsible for elevating the level of ATP inside these bacteria during acid adaptation has been unclear. E. coli uses several mechanisms of ATP production, including oxidative phosphorylation, glycolysis and the oxidation of organic compounds. To uncover which is primarily used during adaptation to acidic conditions, we broadly analyzed the levels of gene transcription of multiple E. coli metabolic pathway components. Our findings confirmed that the primary producers of ATP in E. coli undergoing mild acidic stress are the glycolytic enzymes Glk, PykF and Pgk, which are also essential for survival under markedly acidic conditions. By contrast, the transcription of genes related to oxidative phosphorylation was downregulated, despite it being the major producer of ATP in neutral pH environments.

An experimental study on the performance of fine-grained concrete incorporating recycled steel spring exposed to acidic conditions

2020 ◽  
Vol 23 (11) ◽  
pp. 2458-2470
Author(s):  
Ghasem Pachideh ◽  
Majid Gholhaki
Keyword(s):  
Tensile Strength ◽  
Magnesium Sulfate ◽  
Steel Fibers ◽  
Acidic Environment ◽  
Fine Grained ◽  
Strength Tests ◽  
Acidic Conditions ◽  
Acidic Environments ◽  
Recycled Steel ◽  
Standard Steel

This article aims to study the effects of adding steel fibers and galvanized recycled spring on mechanical properties and crack development in the fine-grained concrete exposed to the acidic environment containing magnesium sulfate. To this end, specimens containing 0.3% and 0.6% of steel fibers and springs, respectively, by concrete volume, were built in normal temperature using 10 cm × 20 cm standard steel formworks so as to conduct the compressive and tensile strength tests. All specimens were cured in 28 days exposed to the environment containing 0%, 5%, and 10% of magnesium sulfate. Based on the results, addition of steel fibers and recycled spring improves the compressive and tensile strength by 50% and 60%, respectively. Moreover, the specimens containing recycled spring better withstood against the acidic environments in comparison with the specimens including steel fibers. In general, it was found that due to the negligible difference between the strength of the specimens, the application of metal-recycled spring in the fine-grained concrete is technically and economically justifiable.

UV Protection of Bacteria Under Simulated Martian Conditions

2020 ◽  
Author(s):  
Paul Godin ◽  
Andrew Schuerger ◽  
Casey Moore ◽  
John Moores
Keyword(s):  
Uv Radiation ◽  
Light Transmission ◽  
Uv Protection ◽  
Genus Bacillus ◽  
Short Term ◽  
Planetary Protection ◽  
Microbial Life ◽  
Acidic Conditions ◽  
Acidic Environments ◽  
Martian Regolith

<p>Ultraviolet (UV) irradiation on the surface of Mars is an important factor affecting the survivability of microorganisms on Mars. The possibility of Martian brines made from Fe<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>, MnSO<sub>4</sub>, and MgSO<sub>4</sub> salts providing a habitable niche on Mars via attenuation of UV radiation was investigated on the bacteria Bacillus subtilis and Enterococcus faecalis. Results demonstrated that it is possible for brines containing Fe<sub>2</sub>(SO<sub>4</sub>)<sub>3 </sub>on Mars to provide protection from harmful UV radiation, even at concentrations as low as 0.5%. Brines made from MnSO<sub>4</sub> and MgSO<sub>4</sub>, did not provide significant UV protection and most spores/cells died over the course of short-term experiments.</p> <p>However, Fe<sub>2</sub>(SO<sub>4</sub>)<sub>3 </sub>brines are strongly acidic, and thus, were lethal to E. faecalis. In contrast, B. subtilis, as a spore-forming bacterium resistant to pH extremes, was unaffected by the acidic conditions of the brines and did not experience any significant lethal effects. Any extant microbial life in Martian Fe<sub>2</sub>(SO<sub>4</sub>)<sub>3 </sub>brines (if present) would need to be capable of surviving acidic environments, if these brines are to be considered a possible habitable niche.</p> <p>The results from this work are important to both the search for life on planets with an atmosphere unable to significantly attenuate UV radiation (i.e., like Mars); and for planetary protection, since it is possible that terrestrial bacteria in the genus Bacillus are likely to survive in Fe-sulfate brines on Mars.</p> <p>Furthermore, preliminary work on UV and photosynthetically active radiation (PAR) light transmission and scattering through simulated Martian regolith and rock samples are also presented. Regoliths that block UV but allow for PAR would be likely candidates for supporting bacterial life.</p>

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