Inactivation of biologically active N-methyl-N-nitroso compounds in aqueous solution: effect of various conditions of pH and illumination

1968 ◽  
Vol 46 (8) ◽  
pp. 807-811 ◽  
Author(s):  
D. R. McCalla ◽  
Antoon Reuvers ◽  
Ruth Kitai
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Low Ph ◽  
Biologically Active ◽  
The Other ◽  
Nitroso Compounds ◽  
Breakdown Rates ◽  
Dilute Aqueous Solutions

The rates of decomposition of N-methyl-N′-nitro-N-nitrosoguanidine (NG), N-methyl-N-nitroso-p-toluenesulfonamide (MNTS), N-methyl-N-nitrosourea, and N-methyl-N-nitrosourethane in dilute aqueous solutions at pH levels ranging from 2 to 9 are tabulated. There are considerable differences in the breakdown rates of these compounds. At low pH, MNTS is destroyed several times faster than any of the other compounds, while at pH 7, MNTS is about 100 times as stable as methylnitrosourea. Rates of photochemical destruction of NG and MNTS are also given. Some of the breakdown products have been identified. These data are used to provide tentative explanations for some apparently anomalous biological results.

Tautomeric equilibria and pKa values for 'sulfurous acid' in aqueous solution: a thermodynamic analysis

1979 ◽  
Vol 57 (4) ◽  
pp. 454-457 ◽  
Author(s):  
J. Peter Guthrie
Keyword(s):  
Aqueous Solution ◽  
Free Energy ◽  
Aqueous Solutions ◽  
Equilibrium Constants ◽  
Acid Solutions ◽  
Sulfurous Acid ◽  
Free Energy Of Formation ◽  
Dilute Aqueous Solutions ◽  
Sulfite Ion ◽  
Energy Of Formation

The free energy of formation of dimethyl sulfite in aqueous solution can be calculated as −91.45 ± 0.79 kcal/mol; this calculation required measurement of the solubility of dimethyl sulfite. From this value and the pKa of SO(OH)2, using previously reported methods, the free energy of formation of SO(OH)2 can be calculated to be −129.26 ± 0.89 kcal/mol. Comparison of this value with the value obtained from the free energy of formation of 'sulfurous acid' solutions, calculated from the free energy of formation of sulfite ion and the apparent pKa, values, permits evaluation of the free energy of covalent hydration of SO2 as 1.6 + 1.0 kcal/mol, in agreement with earlier qualitative spectroscopic observations. From the apparent pKa and the anticipated pKa values for the tautomers (SO(OH)2, pK1 = 2.3; HSO2(OH), pK1 = −2.6) it is possible to calculate the free energy change for tautomerization of SO(OH)2 to H—SO2(OH) as +4.5 ± 1.2 kcal/mol. All equilibrium constants required for Scheme 1, describing the species present in dilute aqueous solutions of SO2, have been calculated. In agreement with previous Raman studies the major tautomer of 'bisulfite ion' is calculated to be H—SO3−.

scholarly journals COMPARISON OF L-ASPARAGINE INTERACTIONS WITH PYRIDINE DERIVATIVES, PYRIDOXAL- 5'-PHOSPHATE AND PYRIDOXINE, IN AQUEOUS SOLUTIONS: THERMODYNAMIC ASPECTS

2021 ◽  
Vol 64 (5) ◽  
pp. 12-18
Author(s):  
Elena Yu. Tyunina ◽  
Olga N. Krutova ◽  
Alexandr I. Lytkin
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Aspartic Acid ◽  
Acid Amide ◽  
The Body ◽  
Biologically Active ◽  
Stable Complex ◽  
Thermochemical Study ◽  
Oh Groups ◽  
Heat Effects

Interactions of proteins with various biologically active substances (hormones, drugs, enzymes, etc.) underlie many biochemical processes in the body. As part of the long-term task to studying various aspects of the interaction between model protein compounds and heterocyclic compounds that are into the structure of many enzymes and drugs, the thermochemical study of aqueous solutions containing aspartic acid amide (L-asparagine) and peridoxal-5¢-phosphate was carried out. Calorimetric measurements of the enthalpy of L-asparagine dissolution in an aqueous solution with pyridoxal-5¢-phosphate additives were performed on an ampoule-type isoperibolic dissolution calorimeter at 298.15 K. The error of measuring single heat effects was below 0.2%. The relative combined uncertainty in the measurements of the enthalpies of dissolution was not more than 0.7%. Based on the obtained experimental data and the using the HEAT computer program, the binding constants and thermodynamic parameters (lgK, ΔcG, ΔcH, ΔcS) of the complex formation between the reagents under study were calculated. A comparison of the affinity of amino acids to interaction with pyridoxal-5¢-phosphate and pyridoxine was carried out. The features of their behavior in an aqueous solution are revealed. It is shown that the interaction of L-asparagine with pyridoxine leads to the formation of a more stable complex than with peridoxal-5¢-phosphate. This fact may be explained in terms of a bulky phosphate group that hinders apparently the interaction of POP with aspartic acid amide. In addition, the peridoxal-5¢-phosphate molecule contains intramolecular hydrogen bonds between aldehyde CHO and phenolic OH groups, which must be destroyed by the interaction of peridoxal-5' - phosphate with an amino acid, which requires additional energy expenses. Thus, the selectivity of the interaction and the stability of the formed complexes are mainly regulated by the factors of structural and energy complementarity.

STUDIES ON DICYANOTRIAZOLE: I. THE CONDUCTANCE OF DILUTE AQUEOUS SOLUTIONS OF DICYANOTRIAZOLE AT 25 °C.

1942 ◽  
Vol 20b (8) ◽  
pp. 161-167 ◽  
Author(s):  
E. G. Taylor
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Dissociation Constant ◽  
Experimental Studies ◽  
Equivalent Conductance ◽  
A Value ◽  
Dilute Aqueous Solution ◽  
Dilute Aqueous Solutions

Previous experimental studies of dicyanotriazole have resulted in statements that the compound is an acid comparable in strength with the strong mineral acids.In the present work, measurements of the equivalent conductance of dicyanotriazole in dilute aqueous solution give the dissociation constant of the acid as 3.378 × 10−2 at 25 °C., thus showing it to be an acid possessing about the same strength as dichloracetic acid.The limiting equivalent conductance of dicyanotriazole at 25 °C. is 384.9. The earlier work gave a value of 397.44.

Triggered Cell Release from Shellac-Cells Composite Microcapsules

2013 ◽  
Vol 1498 ◽  
pp. 177-182
Author(s):  
Shwan A. Hamad ◽  
Simeon D. Stoyanov ◽  
Vesselin N. Paunov
Keyword(s):  
Aqueous Solution ◽  
Shear Stress ◽  
Aqueous Solutions ◽  
Slow Release ◽  
Culture Media ◽  
Low Ph ◽  
Yeast Cells ◽  
Triggered Release ◽  
Cell Release ◽  
Ph Range

ABSTRACTWe have fabricated novel shellac-cells composite microcapsules capable of pH-stimulus induced release of cells in a narrow pH range. The microcapsules were produced with yeast cells as a model for probiotics which were co-precipitated from an aqueous solution of ammonium shellac doped with pH-sensitive polyelectrolytes. The yeast cells in the composite shellac-cell microcapsules retained their viability even when treated with aqueous solutions of very low pH and subjected to shear stress. We studied the pH triggered release of cells from these microcapsules and measured their disintegration times. These microcapsules showed versatile responses ranging from slow release to explosive swelling at higher pH depending on the type and concentration of the polyelectrolyte integrated in the shellac microcapsules. We also observed growth-triggered release of cells from these microcapsules upon exposure to culture media. In both cases the cells retained their viability following their release from the microcapsules into the aqueous solution.

THE RADIOLYSIS OF SOME ORGANIC HALOGEN COMPOUNDS IN AQUEOUS SOLUTION

1960 ◽  
Vol 38 (1) ◽  
pp. 77-93 ◽  
Author(s):  
R. J. Woods ◽  
J. W. T. Spinks
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Organic Compounds ◽  
Gamma Rays ◽  
Organic Halogen ◽  
Halogen Compounds ◽  
Dilute Aqueous Solutions ◽  
Saturated Solutions

Dilute aqueous solutions of some halogen-substituted ethanols, acetaldehydes, and acetates have been irradiated with Co60 gamma rays, and the yield of acid products determined. Irradiations were carried out using air-saturated solutions and also solutions from which the air had been displaced by nitrogen or hydrogen. The acid yields are correlated with the structure of the organic compounds.

scholarly journals Two-dimensional monolayer salt nanostructures can spontaneously aggregate rather than dissolve in dilute aqueous solutions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Wenhui Zhao ◽  
Yunxiang Sun ◽  
Weiduo Zhu ◽  
Jian Jiang ◽  
Xiaorong Zhao ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Room Temperature ◽  
Md Simulations ◽  
Free Energy Calculations ◽  
Zigzag Chain ◽  
Two Dimensional ◽  
Nucleation Behavior ◽  
Dilute Aqueous Solution ◽  
Dilute Aqueous Solutions

AbstractIt is well known that NaCl salt crystals can easily dissolve in dilute aqueous solutions at room temperature. Herein, we reported the first computational evidence of a novel salt nucleation behavior at room temperature, i.e., the spontaneous formation of two-dimensional (2D) alkali chloride crystalline/non-crystalline nanostructures in dilute aqueous solution under nanoscale confinement. Microsecond-scale classical molecular dynamics (MD) simulations showed that NaCl or LiCl, initially fully dissolved in confined water, can spontaneously nucleate into 2D monolayer nanostructures with either ordered or disordered morphologies. Notably, the NaCl nanostructures exhibited a 2D crystalline square-unit pattern, whereas the LiCl nanostructures adopted non-crystalline 2D hexagonal ring and/or zigzag chain patterns. These structural patterns appeared to be quite generic, regardless of the water and ion models used in the MD simulations. The generic patterns formed by 2D monolayer NaCl and LiCl nanostructures were also confirmed by ab initio MD simulations. The formation of 2D salt structures in dilute aqueous solution at room temperature is counterintuitive. Free energy calculations indicated that the unexpected spontaneous salt nucleation behavior can be attributed to the nanoscale confinement and strongly compressed hydration shells of ions.

scholarly journals Flotation of copper-bearing shale in solutions of inorganic salts and organic reagents

2017 ◽  
Vol 18 ◽  
pp. 01028
Author(s):  
Tomasz Ratajczak
Keyword(s):  
Aqueous Solution ◽  
Surface Tension ◽  
Aqueous Solutions ◽  
Inorganic Compounds ◽  
Foam Height ◽  
The Other ◽  
Short Chain ◽  
Inorganic Salts ◽  
Reverse Effect ◽  
Organic Reagents

Flotation data on copper-bearing shale in aqueous solutions of inorganic electrolytes (NaCl, Na2SO4, KPF6, NH4Cl) and organic reagents (ethylamine, propylamine) as frothers were presented and discussed. The relationships between shale flotation, surface tension of aqueous solution and foam height during bubbling with air in the flotation system were presented. It has been found that flotation of shale in the presence of inorganic salts the yield was directly proportional to the surface tension of the aqueous solution of salt and inversely proportional to the height of the foam. On the other hand, for organic reagents solutions (short chain amines), a reverse effect has been observed in relation to the inorganic compounds studied, that is the yield of copper-bearing shale flotation and the foam height were inversely proportional to the surface tension of the amine solution.

Disinfection of Fruits with Activated Water

2019 ◽  
Vol 10 ◽  
pp. 1864-1872
Author(s):  
Prof. Teodora P. Popova
Keyword(s):  
Antimicrobial Activity ◽  
Aqueous Solutions ◽  
Antimicrobial Properties ◽  
The Other ◽  
Gram Negative Bacteria ◽  
High Antimicrobial Activity ◽  
Gram Negative ◽  
E Coli ◽  
Number Of Microorganisms ◽  
Lower Effect

The effect of ionized aqueous solutions (anolytes and catholyte) in the processing of fruits (cherries, morellos, and strawberries) for decontamination has been tested. Freshly prepared analytes and catholyte without the addition of salts were used, as well as stored for 7 months anolytes, prepared with 0.5% NaCl and a combination of 0.5% NaCl and 0.5% Na2CO3. The anolyte prepared with a combination of 0.5% NaCl and 0.5% Na2CO3, as well as the anolyte obtained with 0.5% NaCl, exhibit high antimicrobial activity against the surface microflora of strawberries, cherries, and sour cherries. They inactivate E. coli for 15 minutes. The other species of the fam. Enterobacteriaceae were also affected to the maximum extent, as is the total number of microorganisms, especially in cherries and sour cherries. Even stored for 7 months, they largely retain their antimicrobial properties. Anolyte and catholyte, obtained without the addition of salts, showed a lower effect on the total number of microorganisms, but had a significant effect on Gram-negative bacteria, and especially with regard to the sanitary indicative E. coli.

Effect of thermal history of aqueous solutions of KCl on the metastable zone width

1984 ◽  
Vol 49 (3) ◽  
pp. 559-569 ◽  
Author(s):  
Jaroslav Nývlt
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Thermal History ◽  
Equilibrium Solubility ◽  
Metastable Zone Width ◽  
Zone Width ◽  
Preceding Experiment ◽  
History Of ◽  
Metastable Zone ◽  
The Given

The metastable zone width of an aqueous solution of KCI was measured as a function of the time and temperature of overheating above the equilibrium solubility temperature. It has been found that when the experiments follow close upon one another, the parameters of the preceding experiment affect the results of the experiment to follow.The results are interpreted in terms of hypotheses advanced in the literature to account for the effect of thermal history of solution. The plausibility and applicability of these hypotheses are assessed for the given cause of aqueous solution of a well soluble electrolyte.

The reactions of oligoalcohols with arsenic, arsenous, boric and germanic acids

1980 ◽  
Vol 45 (10) ◽  
pp. 2645-2655 ◽  
Author(s):  
Antonín Mikan ◽  
Miloš Bartušek
Keyword(s):  
Aqueous Solutions ◽  
Equilibrium Constants ◽  
Dilute Aqueous Solutions

The reactions of sorbitol, mannitol, adonitol, dulcitol, glucose and glycerol with H3AsO4, H3AsO3, H3BO3 and GeO2 acids in dilute aqueous solutions were studied by potentiometric neutralization titrations. The formation of the following chelates was demonstrated: As(V)L3-, As(III)L(OH)2-, HAs(III)L(OH)2, BL2-, GeL2(OH)- and GeL32- and the equilibrium constants for their formation were found. Conditions for formation of these chelates of organic oligohydroxy compounds are discussed.

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