scholarly journals A study of factors influencing hydration of sodium hyaluronate from compressibility and high-precision densimetric measurements

1983 ◽  
Vol 213 (2) ◽  
pp. 363-369 ◽  
Author(s):  
A Davies ◽  
J Gormally ◽  
E Wyn-Jones ◽  
D J Wedlock ◽  
G O Phillips
Keyword(s):  
Aqueous Solution ◽  
Hyaluronic Acid ◽  
Ionic Strength ◽  
Pure Water ◽  
Bond Formation ◽  
Sodium Hyaluronate ◽  
Type Solution ◽  
Salt Form ◽  
Density Measurements ◽  
Factors Influencing

A study of the factors influencing the hydration of the biopolymer hyaluronic acid was made by compressibility and density measurements. The factors investigated were the hydration changes on glycosidic bond formation, and also the influence of counterion type, solution ionic strength and temperature. The results indicate that, with this biopolymer, the hydration of the glucuronate residue is significantly more than that of the N-acetylglucosamine residue, and further that the biopolymer is less hydrated than the sum of its component monosaccharide residues. Change of the counterion salt form of this polyelectrolyte from univalent to bivalent counterion type (Na+ to Ca2+) leads to a small though significant increase in the total hydration sheath surrounding the polymer. An increase in the background ionic strength of the solvent leads to a quantifiable lowering of the hydration of the polymer at physiological ionic strength compared with its value in salt-free aqueous solution. A decrease in hydration with increase in temperature in the range 20-50 degrees C is the opposite of previous reports, and was observed when the polymer was dissolved both in pure water and in 0.15 M-NaCl.

Substitution reactions on arsenic(V). The formation and hydrolysis of pentaamminearsenatocobalt(III) in aqueous solution

1973 ◽  
Vol 26 (9) ◽  
pp. 1877 ◽  
Author(s):  
TA Beech ◽  
NC Lawrence ◽  
SF Lincoln
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Bond Formation ◽  
The Other ◽  
Substitution Reactions ◽  
Rate Law ◽  
Hydrolysis Of ◽  
Hydrolysis Reactions

The formation of Co(NH3)5HAsO4+ and Co(NH3)5H2AsO42+ conforms to the rate law: ����������� rate = [Co(NH3)5H2O3+](k-1[HAsO42-]+k-2[H2AsO4-]) where k-1 = (11�1)x10-2 l. mol-1 s-1 and k-2 = (120�15)x10-4 l. mol-1 s-1 at 295 K and unit ionic strength. The hydrolysis of the arsenato complex conforms to the rate law: ������ rate = [total arsenato complex](Ka2k1+k2[H+]+k3[H+]2)(Ka2+[H+])-1 where k1 = (290�15)x10-7s-1, k2 = (408�20)x 10-6 s-1, k3 = (670�34)x10-3 l. mol-1 s-1, and pKa2 = 3.30�0.05 at 295 K and unit ionic strength. The formation and hydrolysis reactions proceed through bond formation and cleavage between oxygen and arsenic. The mechanisms of the reactions characterized by k1 and k-1 are considered to be associative substitutions on arsenic(v), but the mechanisms of the other reactions are less certain.

scholarly journals Study of the heterogeneous reaction of O<sub>3</sub> with CH<sub>3</sub>SCH<sub>3</sub> using the wetted-wall flowtube technique

2003 ◽  
Vol 3 (2) ◽  
pp. 1949-1971 ◽  
Author(s):  
M. Barcellos da Rosa ◽  
W. Behnke ◽  
C. Zetzsch
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Transport Model ◽  
Heterogeneous Reaction ◽  
Surface Film ◽  
Pure Water ◽  
Order Rate Constant ◽  
Uv Spectrophotometry ◽  
Henry's Law ◽  
Henry’S Law

Abstract. This work presents the heterogeneous kinetics of the reaction of CH3SCH3 (dimethyl sulphide, DMS) with O3 (ozone) in aqueous solution at different ionic strengths (0, 0.1 and 1.0 M NaCl) using the wetted-wall flowtube (WWFT) technique. Henry's law coefficients of DMS were determined on pure water and on different concentrations of NaCl (0.1 M–4.0 M) in the WWFT from UV spectrophotometric measurements of DMS in the gas phase using a numerical transport model of phase exchange to be H (M atm−1) = 2.16±0.5 at 274.4 K, 1.47±0.3 at 283.4 K, 0.72±0.2 at 291 K, 0.57±0.1 at 303.4 K and 0.33±0.1 at 313.4K on water, on 1.0M NaCl to be H = 1.57±0.4 at 275.7 K, 0.8±0.2 at 291 K and on 4.0 M NaCl to be H = 0.44±0.1 at 275.7 K and 0.16±0.04 at 29 K, showing a significant effect of ionic strength, mu, on the solubility of DMS according to the equation ln H = −4061 T−1 + 0.052 mu2 + 50.9 μ T−1 + 14.0. At concentrations ofDMS(liq) above 50 μ M, UV spectrophotometry of both O3(gas) and DMS(gas) enables us to observe simultaneously the reactive uptake of O3 on DMS solution and the gas-liquid equilibration of DMS along the flowtube. The uptake coefficient, gamma, of O3 on aqueous solutions of DMS, varying between 1 and 15×10−6, showed a square root-dependence on the aqueous DMS concentration (as expected for diffusive penetration into the surface film, where the reaction takes place in aqueous solution). It was smaller on NaCl solution in accord with the lower solubility of O3. The heterogeneous reaction of O3(gas) with DMS(liq) was evaluated from the observations of the second order rate constant (kII) for the homogeneous aqueous reaction O3(liq) + DMS(liq) using a numerical model of radial diffusion and reactive penetration and leading to kII (in units of 10−8M-1 s-1) = 4.1±1.2 at 291.0 K, 2.15±0.65 at 283.4 K and 1.8±0.5 at 274.4 K. Aside from the expected influence on solubility and aqueous-phase diffusion coefficient of both gases there was no significant effect of ionic strength on kII, that was determined for 0.1M NaCl, leading to kII (108M-1 s-1) = 3.2±1.0 at 288 K, 1.7±0.5 at 282 K and 1.3±0.4 at 276 K, and for 1.0 M NaCl, leading to 3.2±1.0 at 288 K, 1.3±0.4 at 282 K and 1.2±0.4 at 276 K, where the error limits include uncertainties of Henry's law constants and diffusion coefficients for DMS and O3.

A flash photolytic investigation of the photosolvolysis of α-(2,6-dimethoxyphenyl)vinyl chloride. Characterization of the 2,6-dimethoxyacetophenone keto–enol system

1993 ◽  
Vol 71 (11) ◽  
pp. 1964-1969 ◽  
Author(s):  
Yvonne Chiang ◽  
Robert Eliason ◽  
Joel Jones ◽  
A. Jerry Kresge ◽  
Kevin L. Evans ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Vinyl Chloride ◽  
Perchloric Acid ◽  
Pure Water ◽  
Acidity Constant ◽  
Transient Species ◽  
Vinyl Cation ◽  
Carbon Acid

Photosolvolysis of α-(2,6-dimethoxyphenyl)vinyl chloride in trifluoroethanol solution at 25 °C was found to produce the α-(2,6-dimethoxyphenyl)vinyl cation as a transient species with the lifetime τ = 1 μs. Addition of water reduced this lifetime markedly, until, at compositions greater than 80% water, it was too short to measure (τ < 20 ns); extrapolation of the data suggests τ = 9 ns in pure water. Hydration of this cation gave the much longer lived enol of 2,6-dimethoxyacetophenone, whose rates of ketonization were measured in dilute perchloric acid and sodium hydroxide solutions. These data, when combined with rates of enolization of the ketone determined by iodine scavenging, give pKE = 6.98 for the keto–enol equilibrium constant in the 2,6-dimethoxyacetophenone system, [Formula: see text] for the acidity constant of the enol ionizing as an oxygen acid, and [Formula: see text] for the acidity constant of the ketone ionizing as a carbon acid; these constants refer to wholly aqueous solution at 25 °C and ionic strength = 0.10 M.

Oxidative Peptide Bond Formation of Glycine-Amino Acid using 2-(Aminomethyl)malononitrile as a Glycine Unit

2021 ◽  
Author(s):  
Xiaoling Wang ◽  
Jing Li ◽  
Yujiro Hayashi
Keyword(s):  
Aqueous Solution ◽  
Amino Acid ◽  
Bond Formation ◽  
Peptide Bond ◽  
Peptide Bond Formation ◽  
Amide Linkage

Amide linkage of glycine-amino acid was synthesized by coupling of substituted 2-(aminomethyl)malononitrile as a C-terminal glycine unit and N-terminal amine using CsOAc and O2 in aqueous solution. This is a...

Meso tetrakis ortho-, meta-, and para-N-alkylpyridiniopor-phyrins: kinetics of copper(II) and zinc(II) incorporation and zinc porphyrin demetalation

2003 ◽  
Vol 07 (03) ◽  
pp. 139-146 ◽  
Author(s):  
Peter Hambright ◽  
Ines Batinić-Haberle ◽  
Ivan Spasojević
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Effective Charge ◽  
Methyl Ethyl ◽  
Ionic Strength Dependence ◽  
Zinc Porphyrin ◽  
Cationic Porphyrin ◽  
Strength Dependence ◽  
Acid Catalyzed ◽  
Kinetics Of

The relative reactivities of the tetrakis( N -alkylpyridinium- X - yl )-porphyrins where X = 4 (alkyl = methyl, ethyl, n -propyl) , X = 3 (methyl) , and X = 2 (methyl, ethyl, n -propyl, n -butyl, n -hexyl, n -octyl) were studied in aqueous solution. From the ionic strength dependence of the metalation rate constants, the effective charge of a particular cationic porphyrin was usually larger when copper(II) rather than zinc(II) was the reactant. The kinetics of ZnOH + incorporation and the acid catalyzed removal of zinc from the porphyrins in 1.0 M HCl were also studied. In general, the more basic 4- (para-) and 3- (meta-) isomers were the most reactive, followed by the less basic 2- (ortho-) methyl to n -butyl derivatives, with the lipophilic ortho n -hexyl and n -octyl porphyrins the least reactive.

Determination of the complexation properties of a crosslinked poly(acrylic acid) gel with copper(II), nickel(II), and lead(II) in dilute aqueous solution

2001 ◽  
Vol 79 (4) ◽  
pp. 370-376 ◽  
Author(s):  
Catherine Morlay ◽  
Yolande Mouginot ◽  
Monique Cromer ◽  
Olivier Vittori
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Acrylic Acid ◽  
Metal Ion ◽  
Conditional Stability ◽  
Binding Properties ◽  
Complex Species ◽  
Complexing Capacity ◽  
Dilute Aqueous Solution ◽  
Poly Acrylic Acid

The possible removal of copper(II), nickel(II), or lead(II) by an insoluble crosslinked poly(acrylic acid) was investigated in dilute aqueous solution. The binding properties of the polymer were examined at pH = 6.0 or 4.0 with an ionic strength of the medium µ = 0.1 or 1.0 M (NaNO3) using differential pulse polarography as an investigation means. The highest complexing capacity of the polyacid was obtained with lead(II) at pH = 6.0 with µ = 0.1 M, 4.8 mmol Pb(II)/g polymer. The conditional stability constants of the complex species formed were determined using the method proposed by Ruzic assuming that only the 1:1 complex species was formed; for lead(II) at pH = 6.0 and µ = 0.1 M, log K' = 5.3 ± 0.2. It appeared that the binding properties of the polymer increased, depending on the metal ion, in the following order: Ni(II) < Cu(II) < Pb(II). The complexing capacity and log K' values decreased with the pH or with an increase of the ionic strength. These results were in agreement with the conclusions of our previous studies of the hydrosoluble linear analogues. Finally, with the insoluble polymer, the log K' values were comparable to those previously obtained with the linear analogue whereas the complexing capacity values expressed in mmol g-1 were slightly lower.Key words: insoluble crosslinked poly(acrylic acid), copper(II), nickel(II), and lead(II) complexation.

Inerte Amminkomplexe als mehrwertige Kationsäuren in wäßriger Lösung / Inert Ammine Complexes as Multivalent Cationic Acids in Aqueous Solution

1980 ◽  
Vol 35 (9) ◽  
pp. 1096-1103 ◽  
Author(s):  
Matthias Kretschmer ◽  
Lutwin Labouvie ◽  
Karl-W. Quirin ◽  
Helmut Wiehn ◽  
Ludwig Heck
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Spectrophotometric Method ◽  
Complex Cation ◽  
Aqua Ligand ◽  
Second Step ◽  
Acidity Constants ◽  
Ammine Complexes ◽  
Temperature Variations ◽  
Enthalpy Changes

Acidity constants of ammine complexes of tetravalent platinum in aqueous solutions have been determined by a spectrophotometric method at very low ionic strengths and extrapolated to zero ionic strength. Temperature variations of pK-values (25 °C and 50 °C) yield thermodynamic parameters for two successive deprotonation steps of hexaammineplatinum(IV), pentaamminechloroplatinum(IV), and tris(ethylenediamine)pla- tinum(IV) complexes and for the deprotonation of pentaammineaquacobalt(III) ion.The enthalpy changes for the first and second steps are similar and range from 50 to 75 kJ/mole while for the aqua ligand of Co(III) 33 kJ/mole are found. The very large dif­ference in the entropy changes (about 70 to 80 J/K mole for the first step and -10 to + 20 J/K mole for the second step) is interpreted by a model of solvation change. The primary hydration sphere of strongly oriented and immobilized water dipoles around the highly charged complex cation is transformed to a hydrogen-bonded solvation sheath when the electric field of the complex is weakened upon release of the first proton.

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