ChemInform Abstract: ACTION OF CHEMICAL REDUCING AGENTS ON THE STABILITY OF THIAZYL CYCLES

1981 ◽  
Vol 12 (12) ◽  
Author(s):  
H. VINCENT ◽  
Y. MONTEIL ◽  
M. P. BERTHET
Keyword(s):  
Reducing Agents ◽  
The Stability

Methods for the Concentration of Bovine Ac-Globulin (Factor V)

1961 ◽  
Vol 06 (03) ◽  
pp. 435-444 ◽  
Author(s):  
Ricardo H. Landaburu ◽  
Walter H. Seegers
Keyword(s):  
Room Temperature ◽  
Barium Carbonate ◽  
Deae Cellulose ◽  
Reducing Agents ◽  
Factor V ◽  
Isoelectric Precipitation ◽  
Stabilizing Agent ◽  
Bovine Plasma ◽  
The Stability

SummaryAn attempt was made to obtain Ac-globulin from bovine plasma. The concentrates contain mostly protein, and phosphorus is also present. The stability characteristics vary from one preparation to another, but in general there was no loss before 1 month in a deep freeze or before 1 week in an icebox, or before 5 hours at room temperature. Reducing agents destroy the activity rapidly. S-acetylmercaptosuccinic anhydride is an effective stabilizing agent. Greatest stability was at pH 6.0.In the purification bovine plasma is adsorbed with barium carbonate and diluted 6-fold with water. Protein is removed at pH 6.0 and the Ac-globulin is precipitated at pH 5.0. Rivanol and alcohol fractionation is followed by chromatography on Amberlite IRC-50 or DEAE-cellulose. The final product is obtained by isoelectric precipitation.

Control of oxidation-reduction potential during Cheddar cheese ripening and its effect on the production of volatile flavour compounds

2016 ◽  
Vol 83 (4) ◽  
pp. 479-486 ◽  
Author(s):  
Veronica Caldeo ◽  
John A Hannon ◽  
Dara-Kate Hickey ◽  
Dave Waldron ◽  
Martin G Wilkinson ◽  
...  
Keyword(s):  
Redox Potential ◽  
Cheddar Cheese ◽  
Principal Component ◽  
Reducing Agents ◽  
Sulphur Compounds ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Volatile Flavour ◽  
Redox Agents ◽  
The Stability

In cheese, a negative oxidation-reduction (redox) potential is required for the stability of aroma, especially that associated with volatile sulphur compounds. To control the redox potential during ripening, redox agents were added to the salted curd of Cheddar cheese before pressing. The control cheese contained only salt, while different oxidising or reducing agents were added with the NaCl to the experimental cheeses. KIO3 (at 0·05, 0·1 and 1%, w/w) was used as the oxidising agent while cysteine (at 2%, w/w) and Na2S2O4 (at 0·05 and 0·1%, w/w) were used as reducing agents. During ripening the redox potential of the cheeses made with the reducing agents did not differ significantly from the control cheese (Eh ≈ −120 mV) while the cheeses made with 0·1 and 0·05% KIO3 had a significantly higher and positive redox potential in the first month of ripening. Cheese made with 1% KIO3 had positive values of redox potential throughout ripening but no starter lactic acid bacteria survived in this cheese; however, numbers of starter organisms in all other cheeses were similar. Principal component analysis (PCA) of the volatile compounds clearly separated the cheeses made with the reducing agents from cheeses made with the oxidising agents at 2 month of ripening. Cheeses with reducing agents were characterized by the presence of sulphur compounds whereas cheeses made with KIO3 were characterized mainly by aldehydes. At 6 month of ripening, separation by PCA was less evident. These findings support the hypothesis that redox potential could be controlled during ripening and that this parameter has an influence on the development of cheese flavour.

Chemical synthesis of disulfide surrogate peptides by using beta-carbon dimethyl modified diaminodiacids

2021 ◽  
Author(s):  
jibin cui ◽  
xiaoxiong wei ◽  
Rui Zhao ◽  
Huixia Zhu ◽  
Jing Shi ◽  
...  
Keyword(s):  
Chemical Synthesis ◽  
Reducing Agents ◽  
Disulfide Bridges ◽  
Promising Strategy ◽  
The Stability

The replacement of disulfide bridges with metabolically stable isosteres is a promising strategy to improve the stability of disulfide-rich polypeptides towards reducing agents and isomerases. Diaminodiacid-based strategy is one of...

scholarly journals Pseudoperoxidase activity of 5-lipoxygenase stimulated by potent benzofuranol and N-hydroxyurea inhibitors of the lipoxygenase reaction

1991 ◽  
Vol 274 (1) ◽  
pp. 287-292 ◽  
Author(s):  
D Riendeau ◽  
J P Falgueyret ◽  
J Guay ◽  
N Ueda ◽  
S Yamamoto
Keyword(s):  
Nordihydroguaiaretic Acid ◽  
Leukotriene B4 ◽  
Reducing Agents ◽  
Lipid Hydroperoxides ◽  
Reverse Phase ◽  
Structural Analogues ◽  
The Stability ◽  
Hydroperoxyoctadecadienoic Acid ◽  
Derivatives Of ◽  
Stimulation Of

The purified 5-lipoxygenase from porcine leukocytes was found to catalyse the degradation of lipid hydroperoxides in the presence of potent inhibitors of the lipoxygenase reaction. Derivatives of diphenyl-N-hydroxyureas, 4-hydroxybenzofurans and 5-hydroxydihydrobenzofurans all stimulated the 5-lipoxygenase-mediated destruction of 13-hydroperoxyoctadecadienoic acid (13-HPOD). The reaction was dependent on inhibitor and hydroperoxide concentrations (1-10 microM) and could not be detected using heat-inactivated enzyme, when ATP and Ca2+ were omitted or when the hydroperoxide was replaced by the corresponding alcohol. The stability of the inhibitors during this pseudoperoxidase reaction was investigated by measuring the recoveries of 5-hydroxy-2-phenethyl-6-(3-phenoxypropyl)-2,3-dihydrobenzofuran and N-(4-chlorophenyl)-N-hydroxy-N'-(3-chlorophenyl)urea from the reaction mixtures using reverse-phase h.p.l.c. By using an equimolar concentration of 13-HPOD and inhibitor (10 microM) and under conditions where 50% of the 13-HPOD was consumed, the concentration of the benzofuranol decreased by 30%, whereas the N-hydroxyurea derivative could be completely recovered from the reaction mixture. A stimulation of the pseudoperoxidase reaction could be detected only with very effective inhibitors of leukotriene B4 biosynthesis by human leucocytes [IC50 (concn. causing 50% inhibition) less than 100 nM], but not with closely related structural analogues of lower potency or other inhibitors such as nordihydroguaiaretic acid, quercetin or the hydroxamate A-64077. These results demonstrate that 5-lipoxygenase possesses a pseudoperoxidase activity and indicate that potent inhibitors in both N-hydroxyurea and benzofuranol series can function as reducing agents for the enzyme.

Action of Chemical Reducing Agents on the Stability of Thiazyl Cycles

1980 ◽  
Vol 471 (1) ◽  
pp. 233-240 ◽  
Author(s):  
H. Vincent ◽  
Y. Monteil ◽  
M. P. Berthet
Keyword(s):  
Reducing Agents ◽  
The Stability

scholarly journals SPECTROSCOPY OF CATALASE

1937 ◽  
Vol 20 (4) ◽  
pp. 631-648 ◽  
Author(s):  
Kurt G. Stern
Keyword(s):  
Carbon Monoxide ◽  
Ferric Iron ◽  
Reducing Agents ◽  
Ultraviolet Region ◽  
Absorption Bands ◽  
Main Absorption Band ◽  
Nitrogen Bases ◽  
Nitrogenous Substances ◽  
The Stability ◽  
Blood Pigment

Catalase is resistant to oxidizing agents; e.g., ferricyanide. It is also resistant to reducing agents; e.g., catalytically activated hydrogen, hydrosulfite, ferrotartrate, cysteine. The hemin group of the enzyme will combine with cyanide, sulfides, nitric oxide, fluoride. It will not combine with carbon monoxide. Catalase is therefore a ferric complex. The stability of the ferric iron in the enzyme toward reducing agents is not due to the structure of the porphyrin with which it is combined. This porphyrin is the protoporphyrin of the blood pigment. In combination with globin (methemoglobin) the ferric iron is readily reduced by the same reagents which have no effect on catalase. The stability of the ferric iron in the enzyme is therefore due to the protein component. It may be that the type of hematin-protein linkage in catalase is the reason for this phenomenon. The suggestion of Bersin (31), that sulfur may participate in this linkage, is interesting but, as yet, has no experimental basis. Hydrazine or pyridine and hydrosulfite convert catalase into hemochromogens containing ferrous iron. But in these hemochromogens the hematin is no longer attached to the protein. This has been replaced by the nitrogenous bases hydrazine and pyridine. Both hemochromogens combine reversibly with carbon monoxide. Photo-dissociation has only been demonstrated in the case of the pyridine hemochromogen. The positions of the absorption bands of catalase and its derivatives are listed in Table II. The main absorption band (Soret's band) of hemin complexes with nitrogenous substances (nitrogen bases, proteins) is situated at the border between the visible and the ultraviolet region of the spectrum. It has now been found that the spectrum of purified liver catalase has a well defined maximum of high extinction in this range, at 409 mµ. This is further evidence for the hemin nature of the enzyme.

scholarly journals Development of smelting technology of refined ferromanganese with special complex reducing agents

2018 ◽  
Vol 61 (9) ◽  
pp. 689-694
Author(s):  
S. O. Baisanov ◽  
A. S. Baisanov ◽  
A. Z. Isagulov ◽  
D. A. Esengaliev ◽  
N. I. Ospanov
Keyword(s):  
Experimental Studies ◽  
Reducing Agents ◽  
Reducing Agent ◽  
Added Value ◽  
Smelting Process ◽  
Internal Stresses ◽  
Technological Parameters ◽  
The Stability ◽  
Special Complex

The role of manganese in the production of steel is exceptionally high. A feature of the silicothermic process of obtaining refined ferromanganese is the large loss of manganese with waste slag. When waste slag is cooled, it crumbles to form a fine dust due to the polymorphic transformation of calcium orthosilicate β-Ca2SiO4  →  γ-Ca2SiO4 at temperature of 450  –  470  °С with an increase in volume by 12.3  %. As the volume increases, considerable internal stresses appear inside the slag, which leads to dispersion of the slags into finely dispersed state during their cooling. This work is devoted to improving the technology of smelting refined ferromanganese grades, using special complex reducing agents. Experiments have been carried out to simulate the smelting process of refined ferromanganese in an ore-thermal refining furnace RCO-0.1 MVA using aluminosilicomanganese (ASM). The technological modes of the smelting process are established, i.e. optimal composition of charge. Charge went evenly without collapses and emissions. The stability of the current load was observed. Thus, the principal possibility of obtaining a refined ferromanganese with the use of a complex ASM alloy as a reducing agent was proved by the largelaboratory experimental melting. The use of ASM as a reducing agent, instead of ferrosilicomanganese, is due to the sufficient content of silicon and aluminum in it. The presence of chemical compounds and solid solutions of iron, silicon and aluminum in ASM should significantly reduce losses of silicon and aluminum for oxidation processes when interacting with air oxygen. And involving ASM alloy in the metallurgical redistribution, in refined ferromanganese smelting, instead of expensive ferrosilicomanganese will make it possible to obtain an alloy with high added value and with the best technological parameters, due to the presence of additional aluminum in it. The results of X-ray phase studies of slag samples show that the mineralogical components are gehlenite, dicalcium silicate and manganosite. It is noted that gelenite in them is the dominant phase, which is a solid solution, preventing the dispersion of slag. As a result of the theoretical and experimental studies, the tasks have been solved - the smelting technology of refined ferromanganese was developed and tested using a special complex reducing agent – ASM.

Open discussion

1982 ◽  
Vol 99 ◽  
pp. 605-613
Author(s):  
P. S. Conti
Keyword(s):  
Buenos Aires ◽  
Large Mass ◽  
List Type ◽  
Common Phenomenon ◽  
Open Discussion ◽  
The Stability ◽  
Ring Nebulae

Conti: One of the main conclusions of the Wolf-Rayet symposium in Buenos Aires was that Wolf-Rayet stars are evolutionary products of massive objects. Some questions:–Do hot helium-rich stars, that are not Wolf-Rayet stars, exist?–What about the stability of helium rich stars of large mass? We know a helium rich star of ∼40 MO. Has the stability something to do with the wind?–Ring nebulae and bubbles : this seems to be a much more common phenomenon than we thought of some years age.–What is the origin of the subtypes? This is important to find a possible matching of scenarios to subtypes.

Symmetric Multistep Methods Revisited: II. Numerical Experiments

1999 ◽  
Vol 173 ◽  
pp. 309-314 ◽  
Author(s):  
T. Fukushima
Keyword(s):  
Multistep Methods ◽  
Computational Time ◽  
Integration Time ◽  
Implicit Methods ◽  
Symmetric Methods ◽  
Celestial Bodies ◽  
The Stability ◽  
Predictor Corrector ◽  
Symmetric Multistep Methods ◽  
Integration Errors

AbstractBy using the stability condition and general formulas developed by Fukushima (1998 = Paper I) we discovered that, just as in the case of the explicit symmetric multistep methods (Quinlan and Tremaine, 1990), when integrating orbital motions of celestial bodies, the implicit symmetric multistep methods used in the predictor-corrector manner lead to integration errors in position which grow linearly with the integration time if the stepsizes adopted are sufficiently small and if the number of corrections is sufficiently large, say two or three. We confirmed also that the symmetric methods (explicit or implicit) would produce the stepsize-dependent instabilities/resonances, which was discovered by A. Toomre in 1991 and confirmed by G.D. Quinlan for some high order explicit methods. Although the implicit methods require twice or more computational time for the same stepsize than the explicit symmetric ones do, they seem to be preferable since they reduce these undesirable features significantly.

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