scholarly journals Crosslinking and Graft Reaction Using Organic Peroxide

2017 ◽  
Vol 90 (10) ◽  
pp. 490-493
Author(s):  
Kenji AOKI
Keyword(s):  
Organic Peroxide ◽  
Graft Reaction

Anti-Mycobacterial Peroxides: A New Class of Agents for Development Against Tuberculosis

2020 ◽  
Vol 16 (3) ◽  
pp. 392-402
Author(s):  
Christiaan W. van der Westhuyzen ◽  
Richard K. Haynes ◽  
Jenny-Lee Panayides ◽  
Ian Wiid ◽  
Christopher J. Parkinson
Keyword(s):  
Subsequent Development ◽  
Antitubercular Activity ◽  
Organic Peroxide ◽  
New Drugs ◽  
Skeletal Myoblast ◽  
Artemisinin Derivatives ◽  
Malaria Therapy ◽  
New Class ◽  
Alternative Approach

Background: With few exceptions, existing tuberculosis drugs were developed many years ago and resistance profiles have emerged. This has created a need for new drugs with discrete modes of action. There is evidence that tuberculosis (like other bacteria) is susceptible to oxidative pressure and this has yet to be properly utilised as a therapeutic approach in a manner similar to that which has proven highly successful in malaria therapy. Objective: To develop an alternative approach to the incorporation of bacterial siderophores that results in the creation of antitubercular peroxidic leads for subsequent development as novel agents against tuberculosis. Methods: Eight novel peroxides were prepared and the antitubercular activity (H37Rv) was compared to existing artemisinin derivatives in vitro. The potential for toxicity was evaluated against the L6 rat skeletal myoblast and HeLa cervical cancer lines in vitro. Results: The addition of a pyrimidinyl residue to an artemisinin or, preferably, a tetraoxane peroxidic structure results in antitubercular activity in vitro. The same effect is not observed in the absence of the pyrimidine or with other heteroaromatic substituents. Conclusion: The incorporation of a pyrimidinyl residue adjacent to the peroxidic function in an organic peroxide results in anti-tubercular activity in an otherwise inactive peroxidic compound. This will be a useful approach for creating oxidative drugs to target tuberculosis.

scholarly journals Complex Regulation of the Organic Hydroperoxide Resistance Gene (ohr) from XanthomonasInvolves OhrR, a Novel Organic Peroxide-Inducible Negative Regulator, and Posttranscriptional Modifications

2001 ◽  
Vol 183 (15) ◽  
pp. 4405-4412 ◽  
Author(s):  
Rojana Sukchawalit ◽  
Suvit Loprasert ◽  
Sopapan Atichartpongkul ◽  
Skorn Mongkolsuk
Keyword(s):  
Secondary Structure ◽  
Organic Peroxide ◽  
Primer Extension ◽  
Negative Regulator ◽  
Rnase Iii ◽  
Stem Loop ◽  
Strong Activity ◽  
Reading Frame ◽  
Bicistronic Mrna

ABSTRACT Analysis of the sequence immediate upstream of ohrrevealed an open reading frame, designated ohrR, with the potential to encode a 17-kDa peptide with moderate amino acid sequence homology to the MarR family of negative regulators of gene expression. ohrR was transcribed as bicistronic mRNA with ohr, while ohr mRNA was found to be 95% monocistronic and 5% bicistronic with ohrR. Expression of both genes was induced by tert-butyl hydroperoxide (tBOOH) treatment. High-level expression ofohrR negatively regulated ohr expression. This repression could be overcome by tBOOH treatment. In vivo promoter analysis showed that the ohrR promoter (P1) has organic peroxide-inducible, strong activity, while the ohrpromoter (P2) has constitutive, weak activity. Only P1 is autoregulated by OhrR. ohr primer extension results revealed three major primer extension products corresponding to the 5′ ends ofohr mRNA, and their levels were strongly induced by tBOOH treatment. Sequence analysis of regions upstream of these sites showed no typical Xanthomonas promoter. Instead, the regions can form a stem-loop secondary structure with the 5′ ends ofohr mRNA located in the loop section. The secondary structure resembles the structure recognized and processed by RNase III enzyme. These findings suggest that the P1 promoter is responsible for tBOOH-induced expression of the ohrR-ohr operon. The bicistronic mRNA is then processed by RNase III-like enzymes to give high levels of ohr mRNA, while ohrR mRNA is rapidly degraded.

Fluoroelastomer Applications for Pollution Control in the Automotive, Petrochemical, and Electric Power Industries

1982 ◽  
Vol 55 (4) ◽  
pp. 1137-1151 ◽  
Author(s):  
R. R. Campbell ◽  
D. A. Stivers ◽  
R. E. Kolb
Keyword(s):  
Tensile Strength ◽  
Sulfuric Acid ◽  
Carbon Black ◽  
Pollution Control ◽  
Acid Resistance ◽  
Organic Peroxide ◽  
Exposed Surface ◽  
Chemical Attack ◽  
Temperature Ranges ◽  
Concentrated Sulfuric Acid

Abstract The effects of percent fluorine, filler, and cure systems on the thermal and acid resistance of fluoroelastomers were evaluated over temperature ranges that would be typical of actual flue duct installations and accelerated conditions such as 275°C for thermal resistance and 149°C for concentrated sulfuric acid resistance. FKM 2176, which contains 65% fluorine by weight, became hard and brittle after two weeks of accelerated air aging at 275°C. The balance of physical properties of FKM 2176 were good when aged at 200°C. FKM 4894, which contains 67% fluorine by weight, retained useful properties after six weeks of accelerated air aging at 275°C. This indicates this material has improved properties for flue duct applications compared to FKM 2176. FKM 4894 filled with MT carbon black had improved retention of tensile strength after aging at 232°C relative to the FKM 4894 filled with SRF/HAF black, Austin Black and litharge. FKM 2176 was totally degraded after aging three days at 149°C in concentrated sulfuric acid. Aging of FKM 4894 in concentrated sulfuric acid at 149°C resulted in a loss of approximately 75 percent of the original tensile and an increase in the elongation, and the appearance of the exposed surface did not indicate chemical attack. Although FKM 4894 was superior to FKM 2176 when aged in sulfuric acid at 149°C, there was little difference between FKM 4894 and FKM 2176 when aged at 121 °C for up to four weeks or after eight weeks at 100°C in concentrated sulfuric acid. Austin Black showed the best retention of tensile of the four filler systems evaluated after aging at 100°C in concentrated sulfuric acid. FKM 4826, which contains 69% fluorine and is vulcanized using organic peroxide and triallyl isocyanurate, has indicated a compatibility with fiberglass that is superior to all fluorocarbon elastomer gums that were tested.

Rheological study of linear high density polyethylenes modified with organic peroxide

Polymer ◽  
2002 ◽  
Vol 43 (9) ◽  
pp. 2711-2720 ◽  
Author(s):  
Claudio J Pérez ◽  
Guillermo A Cassano ◽  
Enrique M Vallés ◽  
Marcelo D Failla ◽  
Lidia M Quinzani
Keyword(s):  
Organic Peroxide ◽  
High Density ◽  
Rheological Study

scholarly journals The inactivation of phenylalanine hydroxylase by 2-amino-4-hydroxy-6,7-dimethyltetrahydropteridine and the aerobic oxidation of the latter. The effects of catalase, dithiothreitol and reduced nicotinamide–adenine dinucleotide

1971 ◽  
Vol 125 (2) ◽  
pp. 563-568 ◽  
Author(s):  
A. Jakubovič ◽  
L. I. Woolf ◽  
E. Chan-Henry
Keyword(s):  
Hydrogen Peroxide ◽  
Nicotinamide Adenine Dinucleotide ◽  
Phenylalanine Hydroxylase ◽  
Liver Extract ◽  
Aerobic Oxidation ◽  
Organic Peroxide ◽  
Nicotinamide Adenine ◽  
Oxidation In Air ◽  
Reduced Nicotinamide Adenine Dinucleotide

1. Phenylalanine hydroxylase is inhibited by its cofactor, 6,7-dimethyltetrahydropterin. The rate of inactivation, which is irreversible, increases with the concentration of cofactor. 2. Catalase, in sufficient amount relative to cofactor, prevents this inactivation. More tyrosine is formed in the presence of added catalase. 3. Dithiothreitol in the presence of liver extract also prevents inactivation of the enzyme by the cofactor and stimulates hydroxylation of phenylalanine, probably by protecting the cofactor from oxidation and regenerating it from a dihydropterin reaction product. Dithiothreitol restores linearity of rate at very low enzyme concentrations. 4. Dimethyltetrahydropterin is unstable when the solution is exposed to air but is stabilized by dithiothreitol the aerobic oxidation of which is greatly accelerated by dimethyltetrahydropterin. 5. NADH together with liver extract stabilizes the cofactor but not phenylalanine hydroxylase. 6. It is suggested that either hydrogen peroxide or an organic peroxide formed by oxidation in air of the cofactor is the substance attacking phenylalanine hydroxylase, dithiothreitol and cofactor.

scholarly journals ДОСЛІДЖЕННЯ ВПЛИВУ ВМІСТУ ПІСКУ ТА МОДИФІКУЮЧИХ ДОБАВОК НА ВЛАСТИВОСТІ ПОЛІМЕРБЕТОННИХ КОМПОЗИЦІЙ

2021 ◽  
Vol 150 (5) ◽  
pp. 103-111
Author(s):  
Д. С. НОВАК ◽  
Н. М. БЕРЕЗНЕНКО ◽  
А. А. СЕРЕДЕНКО ◽  
О. Г. ПІЩУЛІН
Keyword(s):  
Compressive Strength ◽  
Impact Strength ◽  
Polyester Resin ◽  
Organic Peroxide ◽  
Polymer Concrete ◽  
Sand Content ◽  
Hardness Index ◽  
River Sand ◽  
Two Stages ◽  
Strength And Toughness

Purpose. Establishment of the influence of the content of sand and modifying additives on the hardness, compressive strength, and impact strength of polymer concrete compositions. Methodology. Polymer concrete compositions in the form of round pancakes, sticks and bars based on polyester resin of the CHROMOPLAST GP 2000 brand, hardener (organic peroxide for cold curing) of the Luperox K1 brand, cobalt stearate (cobalt salt of stearic acid), styrene and river sand were subject of investigation. Samples of polymer concrete composites were obtained in two stages: 1) mixing the resin with sand 2) the addition of hardener, styrene and cobalt stearate. To obtain a hardened polyester composition, metal forms with bent sides were used; ceramic boats (not enameled) metal molds 2 cm high. Preparation of the composition was carried out in the following sequence: first, resin was mixed with sand, then hardener, cobalt stearate and styrene were added. The following sequence of preparation of the composition also took place: first the resin and hardener were mixed, only then sand mixed with styrene and cobalt stearate was added. The forms were loaded into a heating cabinet and heated to a temperature of 100 °C for 30-40 minutes. After cooling in the form of the product was removed. The hardness, compressive strength and toughness of the developed compositions were investigated by standard methods. Results. It was found that an increase in sand content from 0 to 90% of the mass. in polymer concrete compositions leads to an increase in hardness by ~ 466%, as well as a decrease in compressive strength by ~ 62% and impact strength by ~ 50%. Scientific novelty. An increase in the hardness index and a decrease in the compressive strength and toughness of polymer concrete compositions with an increase in the sand content to 90 % of the mass was established. This is because the sand has a higher hardness than the polyester resin, and accordingly, an increase in its content leads to an increase in the hardness of the composition. The decrease in compressive strength and toughness is due to a decrease in the amount of binder, due to which the composition becomes more fragile. Practical value. The developed polymer concrete compositions can be used in construction, as well as for repairing damaged concrete surfaces and eliminating cracks.

Sign in / Sign up

Export Citation Format

Share Document