A Variation of Favorskii Rearrangement Mechanism Under Weakly Acidic Conditions: The Case of Clobetasol Propionate Degradation in Solution

2020 ◽  
Author(s):  
Yun Tian ◽  
Haoran Zhang ◽  
Zach Zhu ◽  
Li Chen ◽  
Evelyn Wang ◽  
...  
Keyword(s):  
Critical Role ◽  
Clobetasol Propionate ◽  
Comprehensive Investigation ◽  
Favorskii Rearrangement ◽  
Rearrangement Mechanism ◽  
Alkaline Conditions ◽  
Propionate Degradation ◽  
Acidic Conditions

This paper describes our efforts in proposing a novel mechanism for the formation of the major degradant of clobetasol propionate under weakly acidic conditions through a comprehensive investigation. In the proposed mechanism, the key Favorskii intermediate plays a critical role. This variation of the original Favorskii rearrangement, which proceeds only under alkaline conditions, has not been reported before. This mechanism enriches the understanding of the degradation chemistry of corticosteroids containing the α-haloketone moiety on their 17-position.

A Variation of Favorskii Rearrangement Mechanism Under Weakly Acidic Conditions: The Case of Clobetasol Propionate Degradation in Solution

2020 ◽  
Author(s):  
Yun Tian ◽  
Haoran Zhang ◽  
Zach Zhu ◽  
Li Chen ◽  
Evelyn Wang ◽  
...  
Keyword(s):  
Critical Role ◽  
Clobetasol Propionate ◽  
Comprehensive Investigation ◽  
Favorskii Rearrangement ◽  
Rearrangement Mechanism ◽  
Alkaline Conditions ◽  
Propionate Degradation ◽  
Acidic Conditions

This paper describes our efforts in proposing a novel mechanism for the formation of the major degradant of clobetasol propionate under weakly acidic conditions through a comprehensive investigation. In the proposed mechanism, the key Favorskii intermediate plays a critical role. This variation of the original Favorskii rearrangement, which proceeds only under alkaline conditions, has not been reported before. This mechanism enriches the understanding of the degradation chemistry of corticosteroids containing the α-haloketone moiety on their 17-position.

Adsorptive removal of trace oxytetracycline from water by acid-modified zeolite: influencing factors

2013 ◽  
Vol 68 (11) ◽  
pp. 2473-2478 ◽  
Author(s):  
Wenhao An ◽  
Hua Xiao ◽  
Man Yu ◽  
Xiaoyang Chen ◽  
Yuxin Xu ◽  
...  
Keyword(s):  
Humic Acid ◽  
Removal Efficiency ◽  
Natural Zeolite ◽  
Opposite Effect ◽  
Swine Wastewater ◽  
Adsorption Efficiency ◽  
Tetracycline Antibiotics ◽  
Modified Zeolite ◽  
Alkaline Conditions ◽  
Acidic Conditions

Because of the wide use of antibiotics in the livestock industry, trace tetracycline antibiotics are frequently detected in swine wastewater and water bodies near pig farms. Based on natural zeolite, modified zeolite was synthesized by treatment with nitric acid. As one kind of typical tetracyclines, oxytetracycline (OTC) was chosen as the target adsorbate. Removal of trace OTC by modified zeolite and the effects of several main water matrices on OTC adsorption were studied in detail. OTC removal efficiency by acid-modified zeolite was about 90%, compared to less than 20% by natural zeolite. In general, in acidic conditions the removal efficiency of OTC by modified zeolite was about 90%, which was much higher than 20–35% in alkaline conditions. An increase in ionic strength from 0.01 to 1.0 M led to a decrease in adsorption efficiency from 90 to 27%. The presence of 10.0 mg L−1 dissolved humic acid accelerated sorption of OTC on modified zeolite, while 100.0 mg L−1 humic acid resulted in the opposite effect. An increase in temperature contributed to enhancing the adsorption efficiency.

Effect of acidity on the properties of silica-aluminas synthesized by sol-gel method

2020 ◽  
Vol 63 (7) ◽  
pp. 126-132
Author(s):  
Lyubov V. Furda ◽  
◽  
Evgenia A. Tarasenko ◽  
Sofya N. Dudina ◽  
Olga E. Lebedeva ◽  
...  
Keyword(s):  
Surface Area ◽  
Sol Gel ◽  
Molar Ratio ◽  
Active Centers ◽  
Indicator Method ◽  
Synthesis Conditions ◽  
Alkaline Conditions ◽  
Acidic Conditions ◽  
Amphoteric Properties ◽  
Hydrolysis Of

In the present work amorphous silica-aluminas were synthesized by the coprecipitation method during the hydrolysis of an alcohol solution of tetraethoxysilane (with a tetraethoxysilane: alcohol mass ratio of 1: 1) and 6% aqueous solution of aluminum nitrate at pH values of 1, 3, and 10. The Si/Al molar ratio for all synthesized samples were 4.72 (± 0.29). The amorphous character of the investigated materials was confirmed by X-ray phase analysis. According to the results of scanning electron microscopy, it was found that the resulting powders have particles with a size of 1-20 μm. It was shown that the conditions of synthesis affected the specific surface area and porosity of the materials under study. By the method of low-temperature adsorption-thermodesorption of nitrogen it was established that silica-aluminas obtained under acidic conditions were microporous materials. For the sample obtained under alkaline conditions (pH = 10), the contribution of macropores is very significant. A decrease in surface area is observed as the pH of the synthesis increases. The Hammett indicator method was used to identify and quantify surface centers of different acidity. All studied silica-aluminas are characterized by the presence of both Brønsted basic (pKax from 7 to 12.8) and acidic (pKax from 0 to 7) centers, and Lewis basic (pKax from -4.4 to 0) with a pronounced maximum at pKax = 1.02. It was found that the synthesis conditions had a significant effect on the concentration of active centers. The values of the Hammett function are practically the same for the 3 studied silica-aluminas and describe the studied samples as materials of medium acidity. The variety of Lewis and Brønsted centers on the surface indicates the amphoteric properties of the materials under study. This gives the samples the properties of polyfunctional sorbents and catalysts.

scholarly journals More than Nutrition: Therapeutic Potential of Breast Milk-Derived Exosomes in Cancer

2020 ◽  
Vol 21 (19) ◽  
pp. 7327
Author(s):  
Ki-Uk Kim ◽  
Wan-Hoon Kim ◽  
Chi Hwan Jeong ◽  
Dae Yong Yi ◽  
Hyeyoung Min
Keyword(s):  
Breast Milk ◽  
Therapeutic Potential ◽  
Critical Role ◽  
Drug Carriers ◽  
Enzymatic Digestion ◽  
Lymphocytic Leukemia ◽  
Human Breast Milk ◽  
Exosomal Mirnas ◽  
Acidic Conditions ◽  
Low Prevalence

Human breast milk (HBM) is an irreplaceable source of nutrition for early infant growth and development. Breast-fed children are known to have a low prevalence and reduced risk of various diseases, such as necrotizing enterocolitis, gastroenteritis, acute lymphocytic leukemia, and acute myeloid leukemia. In recent years, HBM has been found to contain a microbiome, extracellular vesicles or exosomes, and microRNAs, as well as nutritional components and non-nutritional proteins, including immunoregulatory proteins, hormones, and growth factors. Especially, the milk-derived exosomes exert various physiological and therapeutic function in cell proliferation, inflammation, immunomodulation, and cancer, which are mainly attributed to their cargo molecules such as proteins and microRNAs. The exosomal miRNAs are protected from enzymatic digestion and acidic conditions, and play a critical role in immune regulation and cancer. In addition, the milk-derived exosomes are developed as drug carriers for delivering small molecules and siRNA to tumor sites. In this review, we examined the various components of HBM and their therapeutic potential, in particular of exosomes and microRNAs, towards cancer.

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 Intervention of Bro1 in pH-Responsive Rim20 Localization in Saccharomyces cerevisiae

2010 ◽  
Vol 9 (4) ◽  
pp. 532-538 ◽  
Author(s):  
Jacob H. Boysen ◽  
Shoba Subramanian ◽  
Aaron P. Mitchell
Keyword(s):  
Target Genes ◽  
Fluorescent Protein ◽  
Growth Conditions ◽  
Yeast Cells ◽  
Endosomal Trafficking ◽  
The Novel ◽  
Pathway Activation ◽  
Alkaline Conditions ◽  
Acidic Conditions ◽  
Green Fluorescent

ABSTRACT Yeast cells contain two Bro1 domain proteins: Bro1, which is required for endosomal trafficking, and Rim20, which is required for the response to the external pH via the Rim101 pathway. Rim20 associates with endosomal structures under alkaline growth conditions, when it promotes activation of Rim101 through proteolytic cleavage. We report here that the pH-dependent localization of Rim20 is contingent on the amount of Bro1 in the cell. Cells that lack Bro1 have increased endosomal Rim20-green fluorescent protein (GFP) under acidic conditions; cells that overexpress Bro1 have reduced endosomal Rim20-GFP under acidic or alkaline conditions. The novel endosomal association of Rim20-GFP in the absence of Bro1 requires ESCRT components including Vps27 but not specific Rim101 pathway components such as Dfg16. Vps27 influences the localization of Bro1 but is not required for RIM101 pathway activation in wild-type cells, thus suggesting that Rim20 enters the Bro1 localization pathway when a vacancy exists. Despite altered localization of Rim20, the lack of Bro1 does not bypass the need for signaling protein Dfg16 to activate Rim101, as evidenced by the expression levels of the Rim101 target genes RIM8 and SMP1. Therefore, endosomal association of Rim20 is not sufficient to promote Rim101 activation.

scholarly journals Symbiotic and non-symbiotic members of the genus Ensifer (syn. Sinorhizobium) are separated into two clades based on comparative genomics and high-throughput phenotyping

2020 ◽  
Author(s):  
Camilla Fagorzi ◽  
Alexandru Ilie ◽  
Francesca Decorosi ◽  
Lisa Cangioli ◽  
Carlo Viti ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Comparative Genomics ◽  
Phylogenetic Analyses ◽  
Carbon Sources ◽  
Associated Bacteria ◽  
Phenotypic Differences ◽  
Genetic Features ◽  
Alkaline Conditions ◽  
High Throughput Phenotyping ◽  
Acidic Conditions

ABSTRACTRhizobium – legume symbioses serve as a paradigmatic example for the study of mutualism evolution. The genus Ensifer (syn. Sinorhizobium) contains diverse plant-associated bacteria, a subset of which can fix nitrogen in symbiosis with legumes. To gain insights into the evolution of symbiotic nitrogen fixation (SNF), and inter-kingdom mutualisms more generally, we performed extensive phenotypic, genomic, and phylogenetic analyses of the genus Ensifer. The data suggest that SNF emerged several times within the genus Ensifer, likely through independent horizontal gene transfer events. Yet, the majority (105 of 106) of the Ensifer strains with the nodABC and nifHDK nodulation and nitrogen fixation genes were found within a single, monophyletic clade. Comparative genomics highlighted several differences between the “symbiotic” and “non-symbiotic” clades, including divergences in their pangenome content. Additionally, strains of the symbiotic clade carried 325 fewer genes, on average, and appeared to have fewer rRNA operons than strains of the non-symbiotic clade. Characterizing a subset of ten Ensifer strains identified several phenotypic differences between the clades. Strains of the non-symbiotic clade could catabolize 25% more carbon sources, on average, than strains of the symbiotic clade, and they were better able to grow in LB medium and tolerate alkaline conditions. On the other hand, strains of the symbiotic clade were better able to tolerate heat stress and acidic conditions. We suggest that these data support the division of the genus Ensifer into two main subgroups, as well as the hypothesis that pre-existing genetic features are required to facilitate the evolution of SNF in bacteria.

scholarly journals pH-Dependent Degradation of Diclofenac by a Tunnel-Structured Manganese Oxide

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2203
Author(s):  
Ching-Yao Hu ◽  
Yu-Jung Liu ◽  
Wen-Hui Kuan
Keyword(s):  
Formation Control ◽  
High Performance ◽  
Degradation Kinetics ◽  
Removal Rate ◽  
Solution Ph ◽  
Mn Oxide ◽  
Highly Active ◽  
Alkaline Conditions ◽  
Acidic Conditions ◽  
Key Parameter

The mechanism of diclofenac (DIC) degradation by tunnel-structured γ-MnO2, with superior oxidative and catalytic abilities, was determined in terms of solution pH. High-performance liquid chromatography with mass spectroscopy (HPLC–MS) was used to identify intermediates and final products of DIC degradation. DIC can be efficiently oxidized by γ-MnO2 in an acidic medium, and the removal rate decreased significantly under neutral and alkaline conditions. The developed model can successfully fit DIC degradation kinetics and demonstrates electron transfer control under acidic conditions and precursor complex formation control mechanism under neutral to alkaline conditions, in which the pH extent for two mechanisms exactly corresponds to the distribution percentage of ionized species of DIC. We also found surface reactive sites (Srxn), a key parameter in the kinetic model for mechanism determination, to be exactly a function of solution pH and MnO2 dosage. The main products of oxidation with a highly active hydroxylation pathway on the tunnel-structured Mn-oxide are 5-iminoquinone DIC, hydroxyl-DIC, and 2,6-dichloro-N-o-tolylbenzenamine.

scholarly journals Antimicrobial activity of DU-6681a, a parent compound of novel oral carbapenem DZ-2640.

1997 ◽  
Vol 41 (6) ◽  
pp. 1260-1268 ◽  
Author(s):  
M Tanaka ◽  
M Hohmura ◽  
T Nishi ◽  
K Sato ◽  
I Hayakawa
Keyword(s):  
Parent Compound ◽  
Inoculum Size ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Alkaline Conditions ◽  
In Vitro Antibacterial Activity ◽  
Acidic Conditions ◽  
Kill Curve ◽  
Time Kill

The in vitro antibacterial activity of DU-6681a, a parent compound of DZ-2640, against gram-positive and -negative bacteria was compared with those of penems and cephalosporins currently available. MICs at which 90% of the isolates are inhibited (MIC90s) of the compound for clinical isolates of methicillin-susceptible and -resistant Staphylococcus aureus and Staphylococcus epidermidis, including methicillin-susceptible and -resistant strains, were 0.10, 25, and 12.5 microg/ml, respectively. DU-6681a inhibited the growth of all strains of Streptococcus pyogenes and of penicillin-susceptible and -insusceptible Streptococcus pneumoniae at 0.006, 0.025, and 0.20 microg/ml, respectively, and MIC90s of the compound were 6.25 and >100 microg/ml for Enterococcus faecalis and Enterococcus faecium, respectively. MIC90s of DU-6681a were 0.20, 0.10, and 0.025 microg/ml for Haemophilus influenzae, Moraxella catarrhalis, and Neisseria gonorrhoeae, respectively. For Pseudomonas aeruginosa, the MIC50 and MIC90 of DU-6681a were 25 and 50 microg/ml, respectively. DU-6681a activity was not affected by different media, varied inoculum size (10(4) to 10(7) CFU), or the addition of human serum but was decreased under acidic conditions against gram-negative bacteria, under alkaline conditions against gram-positive bacteria, and in human urine, as was the activity of the other antibiotics tested. The frequency of spontaneous resistance to DU-6681a was less than or equal to those of the reference compounds. Time-kill curve studies demonstrated the bactericidal action of DU-6681a against S. aureus, S. pneumoniae, Escherichia coli, and H. influenzae.

scholarly journals Bis(zinc(II)-dipicolylamine)-functionalized sub-2 μm core-shell microspheres for the analysis of N-phosphoproteome

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Yechen Hu ◽  
Bo Jiang ◽  
Yejing Weng ◽  
Zhigang Sui ◽  
Baofeng Zhao ◽  
...  
Keyword(s):  
Critical Role ◽  
Core Shell ◽  
Central Metabolism ◽  
Biological Functions ◽  
Silica Microspheres ◽  
Acidic Conditions ◽  
Neutral Conditions ◽  
Phosphate Groups ◽  
Enrichment Methods

AbstractProtein N-phosphorylation plays a critical role in central metabolism and two/multicomponent signaling of prokaryotes. However, the current enrichment methods for O-phosphopeptides are not preferred for N-phosphopeptides due to the intrinsic lability of P-N bond under acidic conditions. Therefore, the effective N-phosphoproteome analysis remains challenging. Herein, bis(zinc(II)-dipicolylamine)-functionalized sub-2 μm core-shell silica microspheres (SiO2@DpaZn) are tailored for rapid and effective N-phosphopeptides enrichment. Due to the coordination of phosphate groups to Zn(II), N-phosphopeptides can be effectively captured under neutral conditions. Moreover, the method is successfully applied to an E.coli and HeLa N-phosphoproteome study. These results further broaden the range of methods for the discovery of N-phosphoproteins with significant biological functions.

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