Hydrolysis and Condensation of Hydrophilic Alkoxysilanes Under Acidic Conditions

Background: Nε-acetyl L-α lysine is an unusual acetylated di-amino acid synthesized and accumulated by certain halophiles under osmotic stress. Osmolytes are generally known to protect proteins and other cellular components under various stress conditions. Objective: The structural and functional stability imparted by Nε-acetyl L-lysine on proteins were unknown and hence was studied and compared to other commonly known bacterial osmolytes - ectoine, proline, glycine betaine, trehalose and sucrose. Methods: Effects of osmolytes on the temperature and pH profiles, pH stability and thermodynamic stability of the model enzyme, α-amylase were analyzed. Results: At physiological pH, all the osmolytes under study increased the optimal temperature for enzyme activity and improved the thermodynamic stability of the enzyme. At acidic conditions (pH 3.0), Nε-acetyl L-α lysine and ectoine improved both the catalytic and thermodynamic stability of the enzyme; it was reflected in the increase in residual enzyme activity after incubation of the enzyme at pH 3.0 for 15 min by 60% and 63.5% and the midpoint temperature of unfolding transition by 11°C and 10°C respectively. Conclusion: Such significant protective effects on both activity and stability of α-amylase imparted by addition of Nε-acetyl L-α lysine and ectoine at acidic conditions make these osmolytes interesting candidates for biotechnological applications.

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Preparation of Organized Mesoporous Silica from Sodium Metasilicate Solutions in Alkaline Medium Using Nonionic Surfactants

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20032019 ◽

2003 ◽

Vol 68 (10) ◽

pp. 2019-2031 ◽

Cited By ~ 1

Author(s):

Markéta Zukalová ◽

Jiří Rathouský ◽

Arnošt Zukal

Keyword(s):

Mesoporous Silica ◽

Ethylene Oxide ◽

Sodium Metasilicate ◽

Spherical Particles ◽

Structure Directing Agent ◽

Inorganic Species ◽

Poly Ethylene Oxide ◽

Acidic Conditions ◽

Poly Ethylene ◽

Hydrolysis Of

A new procedure has been developed, which is based on homogeneous precipitation of organized mesoporous silica from an aqueous solution of sodium metasilicate and a nonionic poly(ethylene oxide) surfactant serving as a structure-directing agent. The decrease in pH, which induces the polycondensation of silica, is achieved by hydrolysis of ethyl acetate. Owing to the complexation of Na+ cations by poly(ethylene oxide) segments, assembling of the mesostructure appears to occur under electrostatic control by the S0Na+I- pathway, where S0 and I- are surfactant and inorganic species, respectively. As the complexation of Na+ cations causes extended conformation of poly(ethylene oxide) segments, the pore size and pore volume of organized mesoporous silica increase in comparison with materials prepared under neutral or acidic conditions. The assembling of particles can be fully separated from their solidification, which results in the formation of highly regular spherical particles of mesoporous silica.

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DETERMINATION OF A SUITABLE CONDITION OF GRAFT COPOLYMERIZATION OF VINYLTRIETHOXYSILANE ONTO NR TO FORM NANOMATRIX STRUCTURE

Rubber Chemistry and Technology ◽

10.5254/rct.18.81545 ◽

2018 ◽

Vol 91 (4) ◽

pp. 767-775 ◽

Cited By ~ 2

Author(s):

Yuanbing Zhou ◽

Yoshimasa Yamamoto ◽

Seiichi Kawahara

Keyword(s):

Silica Nanoparticles ◽

Graft Copolymerization ◽

Monomer Concentration ◽

Minor Component ◽

Suitable Condition ◽

Average Diameter ◽

Silica Matrix ◽

Rubber Particles ◽

Hydrolysis And Condensation ◽

Nanomatrix Structure

ABSTRACT Graft copolymerization of vinyltriethoxysilane (VTES) onto NR particles in the latex stage is a unique reaction, since it occurs together with hydrolysis and condensation of the triethoxysilane group of VTES to form a colloidal silica linking to the rubber particles. These reactions may contribute to the formation of a silica nanomatrix structure that consists of a dispersoid of rubber particles as the major component and a silica matrix as the minor component. Here, the graft copolymerization of VTES followed by hydrolysis and condensation is investigated to determine a suitable condition to prepare NR with a silica nanomatrix structure. The mechanical properties of the resulting graft copolymer are discussed in relation to the morphology, silica content, and gel content of the rubber. Based on morphological observations, NR particles with an average diameter of approximately 1 μm are well dispersed in a nanomatrix consisting of silica nanoparticles. The thickness of the silica nanomatrix increases as the monomer concentration increases, and a long incubation time generates large silica nanoparticles. The tensile strength and viscoelastic properties are significantly improved by forming the silica nanomatrix structure, with its continuous structure that prevents the NR particles from merging.

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The Hsp60 Protein of Helicobacter Pylori Exhibits Chaperone and ATPase Activities at Elevated Temperatures

BioChem ◽

10.3390/biochem1010002 ◽

2021 ◽

Vol 1 (1) ◽

pp. 19-25

Author(s):

Jose A. Mendoza ◽

Julian L. Ignacio ◽

Christopher M. Buckley

Keyword(s):

Helicobacter Pylori ◽

Heat Stress ◽

Molecular Chaperone ◽

Elevated Temperatures ◽

Citrate Synthase ◽

Gastric Epithelium ◽

Acidic Conditions ◽

H Pylori ◽

Induced Aggregation ◽

Hydrolysis Of

The heat-shock protein, Hsp60, is one of the most abundant proteins in Helicobacter pylori. Given its sequence homology to the Escherichia coli Hsp60 or GroEL, Hsp60 from H. pylori would be expected to function as a molecular chaperone in this organism. H. pylori is a type of bacteria that grows on the gastric epithelium, where the pH can fluctuate between neutral and 4.5, and the intracellular pH can be as low as 5.0. We previously showed that Hsp60 functions as a chaperone under acidic conditions. However, no reports have been made on the ability of Hsp60 to function as a molecular chaperone under other stressful conditions, such as heat stress or elevated temperatures. We report here that Hsp60 could suppress the heat-induced aggregation of the enzymes rhodanese, malate dehydrogenase, citrate synthase, and lactate dehydrogenase. Moreover, Hsp60 was found to have a potassium and magnesium-dependent ATPase activity that was stimulated at elevated temperatures. Although, Hsp60 was found to bind GTP, the hydrolysis of this nucleotide could not be observed. Our results show that Hsp60 from H. pylori can function as a molecular chaperone under conditions of heat stress.

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Polyoxometalate based ionic crystal: dual applications in selective colorimetric sensor for hydrated ZnCl2 and antimicrobial activity

New Journal of Chemistry ◽

10.1039/d1nj00138h ◽

2021 ◽

Vol 45 (12) ◽

pp. 5576-5588

Author(s):

C. Sabarinathan ◽

M. Karthikeyan ◽

R. M. Murugappan ◽

Savarimuthu Philip Anthony ◽

Bhaskaran Shankar ◽

...

Keyword(s):

Antimicrobial Activity ◽

Ionic Crystal ◽

Colorimetric Sensor ◽

Icp Oes ◽

One Pot ◽

One Pot Synthesis ◽

Acidic Conditions

One-pot synthesis of POM-salt ([Himi]4[SiMo12O40] (1)) was achieved by mixing silicomolybdic acid and imidazole in acidic conditions and characterized by FTIR, TGA, SEM, EDX, ICP-OES and XPS.

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Prediction of Sodium Substitution Sites in Octacalcium Phosphate: The Relationships of Ionic Pair Ratios in Reacting Solutions

Ceramics ◽

10.3390/ceramics4020018 ◽

2021 ◽

Vol 4 (2) ◽

pp. 240-248

Author(s):

Yuki Sugiura ◽

Masanori Horie

Keyword(s):

Dicarboxylic Acid ◽

Experimental Studies ◽

Ionic Species ◽

Octacalcium Phosphate ◽

Pair Formation ◽

Formation Processes ◽

Ionic Pair ◽

Substitution Process ◽

Sodium Substitution ◽

Acidic Conditions

Octacalcium phosphate (OCP) is widely used in biomaterial fabrication by virtue of its unique crystal structure and low environmental loading. Although various ion and molecule substitution methods into the OCP unit lattice have been introduced, it remains unclear which factors and mechanisms dominate the substitution process. Experimental studies have indicated that Na alkali metal ions are substituted at the P3 PO4 conjugated site in acidic to weakly acidic conditions and the P5 PO4 conjugated site in neutral to weak basic conditions. Ionic species calculation methods have indicated that the pair ratios of Na and HPO42− (NaHPO4−) are small in acidic reacting solutions but large under weakly basic conditions. Consequently, the roles played by NaHPO4− and ionic pair formation processes are thought to dominate ion and molecule substitution into the OCP unit lattice. Such ionic pair formation strongly inhibits dicarboxylic acid substitution into the OCP unit lattice due to the replacement of the Ca ion, which conjugates P5 PO4 as an anchor of dicarboxylic acid.

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pH-Tolerant giant vesicles composed of cationic lipids with imine linkages and oleic acids

RSC Advances ◽

10.1039/d0ra06822e ◽

2020 ◽

Vol 10 (56) ◽

pp. 34247-34253

Author(s):

Daichi Sawada ◽

Ayana Hirono ◽

Kouichi Asakura ◽

Taisuke Banno

Keyword(s):

Oleic Acid ◽

Cationic Lipids ◽

Giant Vesicles ◽

Acidic Conditions

Giant vesicles composed of cationic lipids having an imine linkage and oleic acid were stable at strong acidic conditions.

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Synthesis and Antiproliferative Activity of Phosphorus Substituted 4-Cyanooxazolines, 2-Aminocyanooxazolines, 2-Iminocyanooxazolidines and 2-Aminocyanothiazolines by Rearrangement of Cyanoaziridines

Molecules ◽

10.3390/molecules26144265 ◽

2021 ◽

Vol 26 (14) ◽

pp. 4265

Author(s):

Victor Carramiñana ◽

Ana M. Ochoa de Ochoa de Retana ◽

Francisco Palacios ◽

Jesús M. de los de los Santos

Keyword(s):

Ring Opening ◽

Human Lung ◽

Ring Expansion ◽

Moderate Activity ◽

A549 Cell Line ◽

One Pot ◽

Acidic Conditions ◽

Lung Adenocarcinoma A549 ◽

High Yields

Several phosphorus-substituted N-acylated cyanoaziridines 2 and N-carbamoylated cyanoziridines 5 were prepared in good to high yields. N-Acylated cyanoaziridines 2 were used, after ring expansion, in an efficient synthesis of oxazoline derivative 3a and in a completely regio-controlled reaction in the presence of NaI. Conversely, N-carbamoyl cyanoaziridines 5 reacted with NaI to obtain a regioisomeric mixture of 2-aminocyanooxazolines 7. Mild acidic conditions can be used for the isomerization of N-thiocarbamoyl cyanoaziridine 6a into a 2-aminocyanothiazoline derivative 8a by using BF3·OEt2 as a Lewis acid. Likewise, a one pot reaction of NH-cyanoaziridines 1 with isocyanates obtained 2-iminocyanooxazolidines 9 regioselectively. This synthetic methodology involves the addition of isocyanates to starting cyanoaziridines to obtain N-carbamoyl cyanoaziridines 5, which after the ring opening, reacts with a second equivalent of isocyanate to give the final 2-imino cyanooxazolidines 9. In addition, the cytotoxic effect on the cell lines derived from human lung adenocarcinoma (A549) was also screened. 2-Iminooxazolidines 9 exhibited moderate activity against the A549 cell line in vitro. Furthermore, a selectivity towards cancer cells (A549) over non-malignant cells (MCR-5) was detected.

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Direct synthesis of carbon microspheres under acidic conditions and fenofibrate release

Materials Letters ◽

10.1016/j.matlet.2015.10.151 ◽

2016 ◽

Vol 164 ◽

pp. 156-159 ◽

Cited By ~ 4

Author(s):

Xiufang Wang ◽

Xiaojing Zhu ◽

Sha Wang ◽

Yufang Pan ◽

Yong Tian

Keyword(s):

Direct Synthesis ◽

Carbon Microspheres ◽

Acidic Conditions

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Modified Rhamnogalacturonan-Rich Apple Pectin-Derived Structures: The Relation between Their Structural Characteristics and Emulsifying and Emulsion-Stabilizing Properties

Foods ◽

10.3390/foods10071586 ◽

2021 ◽

Vol 10 (7) ◽

pp. 1586

Author(s):

Jessika N. Humerez-Flores ◽

Sarah H. E. Verkempinck ◽

Clare Kyomugasho ◽

Paula Moldenaers ◽

Ann M. Van Loey ◽

...

Keyword(s):

Emulsion Stability ◽

Structural Characteristics ◽

Stability Study ◽

Natural Food ◽

Apple Pectin ◽

Oil Droplets ◽

Food Ingredients ◽

Acidic Conditions ◽

Hydrolysis Of ◽

Subsequent Acid

In the context of the increasing interest in natural food ingredients, the emulsifying and emulsion-stabilizing properties of three rhamnogalacturonan-rich apple pectin-derived samples were assessed by evaluating a range of physicochemical properties. An apple pectin (AP74) was structurally modified by a β-eliminative reaction to obtain a RG-I-rich pectin sample (AP-RG). Subsequent acid hydrolysis of AP-RG led to the generation of pectin material with partially removed side chains (in particular arabinose depleted) (AP-RG-hydrolyzed), thus exhibiting differences in rhamnose, arabinose, and galactose in comparison to AP-RG. All samples exhibited surface activity to some extent, especially under acidic conditions (pH 2.5). Furthermore, the viscosity of the samples was assessed in relation to their emulsion-stabilizing properties. In a stability study, it was observed that the non-degraded AP74 sample at pH 2.5 exhibited the best performance among all the apple pectin-derived samples evaluated. This emulsion presented relatively small oil droplets upon emulsion production and was less prone to creaming than the emulsions stabilized by the (lower molecular weight) RG-I-rich materials. The AP-RG and AP-RG-hydrolyzed samples presented a slightly better emulsion stability at pH 6.0 than at pH 2.5. Yet, neither pectin sample was considered having good emulsifying and emulsion-stabilizing properties, indicated by the presence of coalesced and flocculated oil droplets.

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