scholarly journals The Role of Ruthenium on Carbon‐Supported PtRu Catalysts for Electrocatalytic Glycerol Oxidation under Acidic Conditions

ChemCatChem ◽  
2017 ◽  
Vol 9 (9) ◽  
pp. 1683-1690 ◽  
Author(s):  
Youngmin Kim ◽  
Hyun Woo Kim ◽  
Seonhwa Lee ◽  
Jisu Han ◽  
Daewon Lee ◽  
...  
Keyword(s):  
Glycerol Oxidation ◽  
Acidic Conditions ◽  
Ptru Catalysts

scholarly journals Recent insights into nitrite signaling processes in blood

2017 ◽  
Vol 398 (3) ◽  
pp. 319-329 ◽  
Author(s):  
Christine C. Helms ◽  
Xiaohua Liu ◽  
Daniel B. Kim-Shapiro
Keyword(s):  
Nitric Oxide ◽  
Human Physiology ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Nitrite Reduction ◽  
No Production ◽  
The Past ◽  
Acidic Conditions ◽  
Hypoxic Vasodilation

Abstract Nitrite was once thought to be inert in human physiology. However, research over the past few decades has established a link between nitrite and the production of nitric oxide (NO) that is potentiated under hypoxic and acidic conditions. Under this new role nitrite acts as a storage pool for bioavailable NO. The NO so produced is likely to play important roles in decreasing platelet activation, contributing to hypoxic vasodilation and minimizing blood-cell adhesion to endothelial cells. Researchers have proposed multiple mechanisms for nitrite reduction in the blood. However, NO production in blood must somehow overcome rapid scavenging by hemoglobin in order to be effective. Here we review the role of red blood cell hemoglobin in the reduction of nitrite and present recent research into mechanisms that may allow nitric oxide and other reactive nitrogen signaling species to escape the red blood cell.

X-ray and synchrotron diffraction studies of 2-(pyridin-2-yl)-1,10-phenanthroline in the role of ligand for two copper polymorphs or hydrogen bonded with 2,2,6,6-tetramethyl-4-oxopiperidinium hexafluorophosphate

2013 ◽  
Vol 69 (5) ◽  
pp. 498-502 ◽  
Author(s):  
Jeanette A. Krause ◽  
Daoli Zhao ◽  
Sayandev Chatterjee ◽  
Bonnie M. Yeung ◽  
William B. Connick ◽  
...  
Keyword(s):  
Synchrotron Diffraction ◽  
Face To Face ◽  
Monoclinic Form ◽  
Pyramidal Geometry ◽  
Crystallization Conditions ◽  
Acidic Conditions ◽  
Square Pyramidal Geometry ◽  
Triclinic Form ◽  
Hydrogen Bonded

Different extended packing motifs of dichlorido[2-(pyridin-2-yl)-1,10-phenanthroline]copper(II), [CuCl2(C17H11N3)], are obtained, depending on the crystallization conditions. A triclinic form, (I), is obtained from dimethylformamide–diethyl ether or methanol, whereas crystallization from dimethylformamide–water yields a monoclinic form, (II). In each case, the CuIIcentre is in a five-coordinate distorted square-pyramidal geometry. The extended packing for both forms can be described as a highly offset π-stacking arrangement, with interlayer distances of 3.674 (3) and 3.679 (3) Å for forms (I) and (II), respectively. The reaction of diprotonated Pt(tmpip2NCN)Cl [tmpip2NCN = 2,6-bis(2,2,6,6-tetramethylpiperidylmethyl)benzyl] with AgPF6under acidic conditions, followed by the addition of 2-(pyridin-2-yl)-1,10-phenanthroline, results in a hydrogen-bonded cocrystal, 2,2,6,6-tetramethyl-4-oxopiperidinium hexafluorophosphate–2-(pyridin-2-yl)-1,10-phenanthroline (1/1), C9H18NO+·PF6−·C17H11N3, (III). The extended packing maximizes π–π interactions in a parallel face-to-face arrangement, with an interlayer stacking distance of 3.4960 (14) Å.

scholarly journals Role of Ureolytic Activity in Bacillus cereus Nitrogen Metabolism and Acid Survival

2008 ◽  
Vol 74 (8) ◽  
pp. 2370-2378 ◽  
Author(s):  
Maarten Mols ◽  
Tjakko Abee
Keyword(s):  
Bacillus Cereus ◽  
Nitrogen Source ◽  
Nitrogen Metabolism ◽  
Acid Stress ◽  
Main Role ◽  
Strain Atcc ◽  
Acid Shock ◽  
Acidic Conditions ◽  
The Impact

ABSTRACT The presence and activities of urease genes were investigated in 49 clinical, food, and environmental Bacillus cereus isolates. Ten strains were shown to have urease genes, with eight of these strains showing growth on urea as the sole nitrogen source. Two of the urease-positive strains, including the sequenced strain ATCC 10987, could not use urea for growth, despite their capacities to produce active urease. These observations can be explained by the inability of the two strains to use ammonium as a nitrogen source. The impact of urea hydrolysis on acid stress resistance was subsequently assessed among the ureolytic B. cereus strains. However, none of the strains displayed increased fitness under acidic conditions or showed enhanced acid shock survival in the presence of urea. Expression analysis of urease genes in B. cereus ATCC 10987 revealed a low level of expression of these genes and a lack of pH-, nitrogen-, urea-, oxygen-, and growth phase-dependent modulation of mRNA transcription. This is in agreement with the low urease activity observed in strain ATCC 10987 and the other nine strains tested. Although a role for B. cereus ureolytic activity in acid survival cannot be excluded, its main role appears to be in nitrogen metabolism, where ammonium may be provided to the cells in nitrogen-limited, urea-containing environments.

Spectroscopic characterization of free-base hydroxy(arylethynyl)porphyrins in acidic and basic media

2017 ◽  
Vol 21 (10) ◽  
pp. 680-691
Author(s):  
Kaarin K. Evens ◽  
Kathryn E. Splan
Keyword(s):  
Spectroscopic Characterization ◽  
Spectral Features ◽  
Free Base ◽  
Enhanced Absorption ◽  
Spectral Shifts ◽  
Porphyrin Macrocycle ◽  
Show Evidence ◽  
Acidic Conditions

The addition of arylethynyl groups to the porphyrin macrocycle represents an effective strategy with which to enhance the light-harvesting properties of porphyrins. We now extend this modification to arylethynyl porphyrins with two or four [Formula: see text]-hydroxyphenyl substituents. Arylethynyl porphyrins bearing four, but not two, [Formula: see text]-hydroxyphenyl substituents show evidence of aggregation under acidic conditions. Under basic conditions, deprotonation of the peripheral hydroxyphenyl substituents results in substantially red-shifted spectral features and enhanced absorption in the Q-band region. When the hydroxyphenyl groups are appended to the porphyrin macrocylce via the ethynyl spacers, the spectral shifts observed upon deprotonation are significantly enhanced relative to those observed for hydroxyphenylporphyrins, highlighting the role of expanded conjugation in altering porphyrin photophysics.

The new world of inorganic polyphosphates

2016 ◽  
Vol 44 (1) ◽  
pp. 13-17 ◽  
Author(s):  
Cristina Azevedo ◽  
Adolfo Saiardi
Keyword(s):  
Protein Modification ◽  
Biochemical Characterization ◽  
Covalent Attachment ◽  
Detection Methods ◽  
Inorganic Polyphosphate ◽  
Post Translational Modifications ◽  
Topoisomerase 1 ◽  
Lysine Residues ◽  
Acidic Conditions

Post-translational modifications (PTMs) add regulatory features to proteins that help establish the complex functional networks that make up higher organisms. Advances in analytical detection methods have led to the identification of more than 200 types of PTMs. However, some modifications are unstable under the present detection methods, anticipating the existence of further modifications and a much more complex map of PTMs. An example is the recently discovered protein modification polyphosphorylation. Polyphosphorylation is mediated by inorganic polyphosphate (polyP) and represents the covalent attachment of this linear polymer of orthophosphate to lysine residues in target proteins. This modification has eluded MS analysis as both polyP itself and the phosphoramidate bonds created upon its reaction with lysine residues are highly unstable in acidic conditions. Polyphosphorylation detection was only possible through extensive biochemical characterization. Two targets have been identified: nuclear signal recognition 1 (Nsr1) and its interacting partner, topoisomerase 1 (Top1). Polyphosphorylation occurs within a conserved N-terminal polyacidic serine (S) and lysine (K) rich (PASK) cluster. It negatively regulates Nsr1–Top1 interaction and impairs Top1 enzymatic activity, namely relaxing supercoiled DNA. Modulation of cellular levels of polyP regulates Top1 activity by modifying its polyphosphorylation status. Here we discuss the significance of the recently identified new role of inorganic polyP.

Effects of pH on photocatalysis of 2,4,6-trichlorophenol in aqueous TiO2 suspensions

1994 ◽  
Vol 30 (9) ◽  
pp. 47-57 ◽  
Author(s):  
Shuzo Tanaka ◽  
Uttam Kumar Saha
Keyword(s):  
Sodium Chloride ◽  
Degradation Rate ◽  
Parent Compound ◽  
Photocatalytic Decomposition ◽  
Illumination Time ◽  
Effects Of Ph ◽  
Alkaline Conditions ◽  
Na Ions ◽  
Acidic Conditions

The effects of pH on the photocatalytic decomposition of 2,4,6-trichlorophenol (TCP) were investigated in the presence of titanium dioxide suspensions illuminated by a high pressure mercury lamp over the wavelength range of 302-405 nm. Higher degradation rate was observed under alkaline conditions than acidic conditions. Although a rapid adsorption of TCP onto the TiO2 surface was observed at low pH and no adsorption at high pH, the role of adsorption of TCP was found insignificant in photocatalysis. With sodium chloride addition, a decrease in reaction rate was observed at pH 5 due to Cl− ions inhibition, but at pH 10 the same anions had no adverse effect on the measured photocatalytic efficiency and Na+ ions enhanced the degradation rate of TCP. With no oxygen, however, the photocatalytic decomposition of TCP in sodium chloride solution gives lower degradation rate than with dissolved oxygen and no sodium chloride at various pH. Complete mineralization requires a longer illumination time than the decomposition of the parent compound. A mechanism for the reaction based on photogeneration of hydroxyl radicals was proposed.

scholarly journals Gold Sols as Catalysts for Glycerol Oxidation: The Role of Stabilizer

ChemCatChem ◽  
2009 ◽  
Vol 1 (4) ◽  
pp. 510-514 ◽  
Author(s):  
Alberto Villa ◽  
Di Wang ◽  
Dang Sheng Su ◽  
Laura Prati
Keyword(s):  
Glycerol Oxidation

Growth of nanotubes in sol-gel-derived V2O5 powders and films prepared under acidic conditions

2009 ◽  
Vol 24 (2) ◽  
pp. 475-481 ◽  
Author(s):  
R. Ceccato ◽  
S. Dirè ◽  
T. Barone ◽  
G. De Santo ◽  
E. Cazzanelli
Keyword(s):  
Thin Films ◽  
Sol Gel ◽  
Structural Evolution ◽  
Nanocrystalline Phase ◽  
X Ray Diffraction ◽  
Α Phase ◽  
Heat Treated ◽  
Acidic Conditions ◽  
Hydrolysis Conditions

The structural evolution with temperature of some V2O5 gels and thin films is presented, and the role of the hydrolysis conditions is investigated. Several techniques, i.e., x-ray diffraction, differential thermal analysis, infrared, and temperature-dependent Raman spectroscopy, have been used to follow the thermal behavior of the samples. When the bulk xerogels begin to change from a nanocrystalline phase to the orthorhombic α-V2O5, in the temperature range 280 to 300 °C, a growth of vanadium oxide nanotubes also occurs, while at higher temperatures the crystallization into the α phase prevails. A slightly different evolution is observed for heat treated thin films, which show a structure containing polyvanadate chains near room temperature. They also present a growth of nanotubes for intermediate temperatures and a complete crystallization into the α phase when the temperature is further increased.

scholarly journals Biofilms Confer Resistance to Simulated Extra-terrestrial Geochemical Extremes

2017 ◽  
Author(s):  
Adam H. Stevens ◽  
Delma Childers ◽  
Mark Fox-Powell ◽  
Charles S. Cockell
Keyword(s):  
Planktonic Cells ◽  
Planetary Protection ◽  
Aqueous Environments ◽  
Groundwater Systems ◽  
Acidic Conditions ◽  
High Sulfate ◽  
Chemical Conditions ◽  
Physical And Chemical ◽  
Over Time

1AbstractBiofilms improve microbes’ resistance to a variety of extreme physical and chemical conditions on Earth. The discovery of putative aqueous environments on other planetary bodies such as Mars motivates an interest in understanding the viability of life, and the potential role of biofilms, in previously unexplored geochemical extremes. We investigated the loss of viability of planktonic cells and biofilms ofSphingomonas desiccabilis(a Gram-negative, desiccation resistant, soil crust-forming organism) to simulated Martian brines. These brines were produced from geochemical modelling of past aqueous environments on Mars, and their high sulfate concentrations make them different to most terrestrial brines, although similar briny environments have been found in locations such as the Basque Lakes in Canada or in deep subsurface groundwater systems. Biofilms grown on basaltic scoria were subjected to the simulated martian brines and the viability of cells was measured over time and compared to equivalent planktonic cultures. Crystal violet assay was used to measure how the biomass of the biofilms changed over time in response to the brines. While certain brines were highly hostile to microbial viability, we found that biofilms that were desiccated prior to being treated with brines maintained viability over a longer treatment period when compared to planktonic cells. Our results show that biofilms confer short-term protection to the harsh osmotic, ionic, and acidic conditions of Mars-relevant brines. However, in the most extreme simulated brines, even biofilms eventually lost viability. By demonstrating that biofilms confer protection to conditions that are potentially analogous to current day recurrent slope lineae (thought to be produced by the flow of briny fluids) on Mars, our results show that contaminant biofilm-forming microorganisms may have a greater chance of surviving in so-called ‘Special Regions’ on Mars, with implications for planetary protection in missions that aim to explore these regions.

scholarly journals Human parvovirus B19 interacts with globoside under acidic conditions as an essential step in endocytic trafficking

2021 ◽  
Vol 17 (4) ◽  
pp. e1009434
Author(s):  
Jan Bieri ◽  
Remo Leisi ◽  
Cornelia Bircher ◽  
Carlos Ros
Keyword(s):  
Parvovirus B19 ◽  
Endocytic Trafficking ◽  
Erythroid Cells ◽  
Binding Assays ◽  
Essential Step ◽  
Viral Particles ◽  
Internalization Process ◽  
Intracellular Compartments ◽  
Acidic Conditions

The glycosphingolipid (GSL) globoside (Gb4) is essential for parvovirus B19 (B19V) infection. Historically considered the cellular receptor of B19V, the role of Gb4 and its interaction with B19V are controversial. In this study, we applied artificial viral particles, genetically modified cells, and specific competitors to address the interplay between the virus and the GSL. Our findings demonstrate that Gb4 is not involved in the binding or internalization process of the virus into permissive erythroid cells, a function that corresponds to the VP1u cognate receptor. However, Gb4 is essential at a post-internalization step before the delivery of the single-stranded viral DNA into the nucleus. In susceptible erythroid Gb4 knockout cells, incoming viruses were arrested in the endosomal compartment, showing no cytoplasmic spreading of capsids as observed in Gb4-expressing cells. Hemagglutination and binding assays revealed that pH acts as a switch to modulate the affinity between the virus and the GSL. Capsids interact with Gb4 exclusively under acidic conditions and dissociate at neutral pH. Inducing a specific Gb4-mediated attachment to permissive erythroid cells by acidification of the extracellular environment led to a non-infectious uptake of the virus, indicating that low pH-mediated binding to the GSL initiates active membrane processes resulting in vesicle formation. In summary, this study provides mechanistic insight into the interaction of B19V with Gb4. The strict pH-dependent binding to the ubiquitously expressed GSL prevents the redirection of the virus to nonpermissive tissues while promoting the interaction in acidic intracellular compartments as an essential step in infectious endocytic trafficking.

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