The thermodynamics of transfer of DNP-lysine from water to ethanol: A model for antibody-hapten association

The apparent partial molar heat capacities of lysine in water and N-ε-(2,4-dinitrophenyl)-L-lysine (DNP-lysine) in water and ethanol have been determined. In addition, the thermodynamic quantities (ΔG _tr, ΔH _tr, ΔS _tr, ΔC _{p, tr}) associated with the transfer of DNP-lysine from water to ethanol have been estimated. A comparison of these latter values with similar quantities for the interaction of the hapten, DNP-lysine, with its antibody suggest that water-hapten interactions play a significant role in defining the overall thermodynamic changes for the reaction. In particular, it appears that the large negative ΔC _p values measured for hapten-antibody reactions are largely the result of a reduction in water-hapten interactions.     

Effect of solvation on the thermodynamics of formation for 18-crown-6 ether complexes with glycine and triglycine in water-ethanol solutions at 298 K

Using data from calorimetric titration, standard thermodynamic parameters logK ^○, Δ_r G ^○, Δ_r H ^○, and TΔ_r S ^○ of the formation of 18-crown-6 ether (18C6) molecular complex with triglycine (3Gly), [3Gly18C6] in H₂O-EtOH solvents with contents of ethanol x ranging between 0.0 and 0.5 mole fractions are calculated. Increasing the concentration of EtOH in the solvent is found to raise the reaction’s exothermicity from ?5.9 to ?21.0 kJ mol^?1 and logK ^○ [3Gly18C6] from 1.10 to 2.53. A comparative analysis of the effect the composition of H₂O-EtOH solvent has on the reactions of [3Gly18C6] and [Gly18C6] formation is performed. As in case of [Gly18C6] formation, the changes in the complex’s enthalpy of solvation Δ_tr H ^○([3Gly18C6]) are close to the Δ_tr H ^○(18C6) parameter and differ considerably from the Δ_tr H ^○(3Gly) value, testifying to the crucial role 18C6 plays in changing the [3Gly18C6] state of solvation. The ratio between solvation contributions from reagents to Δ_tr G ^○ of [3Gly18C6] formation is found to differ from that the one between the corresponding contributions to Δ_tr H _r ^o : in transferring from water to H₂O-EtOH mixtures, the increase in the positive Δ_tr G ^○(18C6) values is slight and therefore negligible when compared to Δ_tr G ^○(3Gly).     

Evaluation of Gibbs free energy for the transfer of a highly hydrophilic ion from an acidic aqueous solution to an organic solution based on ion pair extraction

A method to determine the standard Gibbs free energy for the transfer, ΔG°_tr, of a highly hydrophilic metal ion from an aqueous solution, W, in the presence of high concentration of H⁺ to an organic solution, O, was proposed based on the theoretical consideration of the distribution process of ions between W and O. The usefulness of the proposed method was verified experimentally by comparing ΔG°_tr of Mg²⁺ determined by the method with that obtained by voltammetry for the ion transfer at the W|O interface. The O examined were nitrobenzene (NB) and 1,2-dichloroethane (DCE). By applying the proposed method, ΔG°_tr of NpO₂⁺, UO₂²⁺, NpO₂²⁺ and PuO₂²⁺ from an acidic W to NB were determined.     

The solvation of L-serine in mixtures of water with some aprotic solvents at 298.15 K

The integral enthalpies of solution Δ_sol H ^m of L-serine in mixtures of water with acetonitrile, 1,4-dioxane, dimethylsulfoxide (DMSO), and acetone were measured by solution calorimetry at organic component concentrations up to 0.31 mole fractions. The standard enthalpies of solution (Δ_sol H°), transfer (Δ_tr H°), and solvation (Δ_solv H°) of L-serine from water into mixed solvents were calculated. The dependences of Δ_sol H°, Δ_solv H°, and Δ_tr H° on the composition of aqueous-organic solvents contained extrema. The calculated enthalpy coefficients of pair interactions of the amino acid with cosolvent molecules were positive and increased in the series acetonitrile, 1,4-dioxane, DMSO, acetone. The results obtained were interpreted from the point of view of various types of interactions in solutions and the influence of the nature of organic solvents on the thermochemical characteristics of solutions.     

The enthalpies of solution of DL-α-alanine in water-organic solvent mixtures at 298.15 K

The integral enthalpies of solution (298.15 K) of DL-α-alanine in water-organic solvent mixtures were measured at organic component concentrations x ₂ = 0–0.4 mole fractions. The organic solvents used were acetonitrile (ACN), formamide (FA), N,N-dimethylformamide (DMFA), and N,N-dimethylsulfoxide (DMSO). The standard enthalpies of solution Δ_sol H ^o, solvation Δ_solv H ^o, and transfer (Δ_tr H ^o) of DL-α-alanine from water to mixed solvents were calculated. The influence of the structure and properties of solutes and mixture composition on solute thermochemical characteristics was considered. The solution of DL-α-alanine in the mixtures studied was endothermic over the whole range of organic component concentrations. The Δ_sol H ^o, Δ_tr H ^o, and Δ_solv H ^o values as functions of x ₂ can pass extrema (DMSO and DMFA), be almost independent of mixed solvent composition (FA), or be exothermic and monotonic functions (ACN). The enthalpy coefficients of pair interactions (h _xy ) between DL-α-alanine and organic solvent molecules were calculated. The linear Kamlet-Taft equation was used to correlate the h _xy values with the properties of organic solvents.     

Temperature and sodium chloride effects on the solubility of anthracene in water

The solubility of anthracene was measured in pure water and in sodium chloride aqueous solution (salt concentration, m/mol · kg^?1 = 0.1006, 0.5056, and 0.6082) at temperatures between (278 and 333) K. Solubility of anthracene in pure water agrees fairly well with values reported in earlier similar studies. Solubility of anthracene in sodium chloride aqueous solutions ranged from (6 · 10^?8 to 143 · 10^?8) mol · kg^?1. Sodium chloride had a salting-out effect on the solubility of anthracene. The salting-out coefficients did not vary significantly with temperature over the range studied. The average salting-out coefficient for anthracene was 0.256 kg · mol^?1.The standard molar Gibbs free energies, Δ_trG°, enthalpies, Δ_trH°, and entropies, Δ_trS°, for the transfer of anthracene from pure water to sodium chloride aqueous solutions were also estimated. Most of the estimated Δ_trG° values were positive [(20 to 1230) J · mol^?1]. The analysis of the thermodynamic parameters shows that the transfer of anthracene from pure water to sodium chloride aqueous solution is thermodynamically unfavorable, and that this unfavorable condition is caused by a decrease in entropy.     

Interactions of Peptides and Lysozyme with Aqueous Tetraethylammonium Bromide at 298.15 K

The apparent molar volumes, V _{ø, 2}, of gly-leu, gly-gly-leu and the partial specific volume ν^° of hen-egg-white lysozyme have been determined in aqueous of TEAB solutions by density measurements at 298.15 K. These data have been used to calculate the infinite dilution apparent molar volumes V _2,m ^o for the peptides in aqueous TEAB solutions and the standard partial molar volumes of transfer Δ_tr V _2,m ^o of the peptides from water to aqueous TEAB solutions. The results on Δ_tr V _2,m ^o of peptides from water to aqueous TEAB solutions have been interpreted in terms of ion-ion, ion-polar, hydrophilic-hydrophilic and hydrophobic-hydrophobic group interactions. In order to supplement this information, enthalpies of transfer of aqueous peptides from water to TEAB solution have been determined at 298.15 K using a VP-ITC titration calorimeter. The data on partial molar volumes and enthalpies of transfer have been discussed in light of various interactions operating in the ternary system of peptides, water and TEAB. The partial specific volume of transfer of lysozyme from water to aqueous TEAB solutions also indicates the predominance of hydrophobic interactions.     

Enthalpy characteristics of solution of L-cysteine and L-asparagine in water-alcohol mixtures at 298.15 K

The integral enthalpies of solution Δ_sol H ^m of L-cysteine and L-asparagine in mixtures of water with ethanol, n-propanol, and isopropanol at a mole fraction of alcohol of up to 0.32 were determined by calorimetry of solution. The standard enthalpies of solution (Δ_sol H ⁰) of L-serine and of its transfer (Δ_tr H ⁰) from water to a mixed solvent were calculated. The dependences of Δ_sol H ⁰ and Δ_tr H ⁰ on the composition of water-alcohol mixtures pass through a maximum. The calculated enthalpy coefficients of pair interaction of amino acids with alcohol molecules are positive and increase in the order ethanol, n-propanol, isopropanol. The data obtained were interpreted from the viewpoint of various types of interaction in solution and effect of the amino acid residue on the thermochemical characteristics of solution.     

Enthalpy characteristics of dissolution of L-tryptophan in water + formamides binary solvents at 298.15 K

Enthalpies of dissolution of L-tryptophan in aqueous solutions of formamide (FA), N-methylformamide (MFA), and N,N-dimethylformamide (DMF) are measured according to calorimetry at the concentration of amides x ₂ = 0?0.4 mole fraction. Standard values of enthalpies of dissolution and transfer Δ_tr H ^o of L-tryptophan from water to binary solvent, as well as enthalpy coefficients of pair-wise interactions h _xy of L-tryptophan with formamide molecules are calculated. The effect the composition of a waterorganic mixture has on the enthalpy characteristics of L-tryptophan is considered. The relation of Δ_tr H ^o of L-tryptophan with the structure of amides is shown. A quantitative estimation of the contributions to the energy of L-tryptophan-formamide pair-wise interactions determined by polarity/polarizability, acidity, and basicity of organic solvent is performed using the four-parameter Kamlet-Taft correlation equation.     

Temperature and salt addition effects on the solubility behaviour of some phenolic compounds in water

Solubility-temperature dependence data for six phenolic compounds (PhC), contained in olive mill wastewater (OMWW), in water and in some chloride salts (KCl, NaCl, and LiCl) aqueous solutions have been presented and solution standard molar enthalpies (Δ_solH^∘) were determined using Van’t Hoff plots. The temperature was varied from 293.15 K to 318.15 K. Solubility data were estimated using a thermostated reactor and HPLC analysis. It has been observed that solubility, in pure water and in aqueous chloride solutions, increases with increasing temperature. The salting-out LiCl > NaCl > KCl order obtained at 298.15 K is confirmed. Results were interpreted in terms of the salt hydration shells and the ability of the solute to form hydrogen-bond with water. The standard molar Gibbs free energies of transfer of PhC (Δ_trG^∘) from pure water to aqueous solutions of the chloride salts have been calculated from the solubility data. In order to estimate the contribution of enthalpic and entropic terms, standard molar enthalpies (Δ_trH^∘) and entropies (Δ_trS^∘) of transfer have also been calculated. The decrease in solubility is correlated to the positive Δ_trG^∘ value which is mainly of enthalpic origin.     

Solvation of ions. XXVII. Comparison of methods to calculate single ion free energies of transfer in mixed solvents

Free energies of transfer of ions from water to mixtures of water with acetonitrile (AN), with dimethylformamide (DMF), with dimethylsulfoxide (DMSO), and with ethylene glycol have been determined using both the tetraphenylarsonium tetraphenylboride [TATB] and the negligible liquid junction potential [E _j ] assumptions. By making use of ΔG _tr (Ag⁺)[TATB]=12 kJ-mol^?1 for transfer from DMSO to AN and by assuming negligible liquid junction potential in the cell $${\text{Ag|AgNO}}_{\text{3}} {\text{(0}}{\text{.01}}M{\text{),S}}\parallel {\text{Et}}_{\text{4}} {\text{NPic(0}}{\text{.1}}M{\text{),AN}}\parallel {\text{AgNO}}_{\text{3}} {\text{(0}}{\text{.01}}M{\text{),AN|Ag}}$$ single ion free energies of transfer of silver ion ΔG _tr (Ag⁺)[E _j ] from DMSO to 35 pure and mixed solvents show a standard deviation of only 2 kJ-mol^?1 when compared with ΔG _tr (Ag⁺) calculated from the TATB assumption that ΔG _tr (Ph ₄ As⁺)=ΔG _tr (Ph ₄ B^?). The ferrocene assumption [Fc] also gives acceptable agreement with ΔG _tr (Ag⁺)[TATB] provided that the solvents are not highly aqueous. Other cells with other junctions give less acceptable agreement between the E _j and TATB assumptions. It is essential that the salt bridge is always tetraethylammonium picrate in AN, if the E _j assumption is assumed. Because of the ease of making potentiometric measurements compared with the difficulty of measurements required for the TATB assumption, the negligible liquid junction potential method in the cell shown is recommended for estimating transfer free energies of single ions. The ferrocene assumption is acceptable only for non-structured aprotic solvents.     

Volumetric, viscometric and refractive index behavior of some α-amino acids in aqueous tetrapropylammonium bromide at different temperatures

Densities, ρ, viscosities, η, and refractive indices, n _D, of glycine (Gly), DL-alanine (Ala), DL-valine (Val) (0.05, 0.10, 0.15, 0.20, 0.25 mol kg^?1), and L-leucine (Leu) (0.02, 0.05, 0.10 mol kg^?1) in water and in 0.20 mol kg^?1 aqueous tetrapropylammonium bromide (TPAB) have been measured at 298.15, 303.15, 308.15, and 313.15 K. The density data have been utilized to calculate apparent molar volumes, ?_v, partial molar volumes at infinite dilution, ?_v°, and partial molar volumes of transfer, ? _v°(tr) of amino acids. The viscosity data have been analyzed by means of Jones-Dole equation to obtain Falkenhagen coefficient, A, and Jones-Dole coefficient, B, free energy of activation of viscous flow per mole of solvent, Δµ₁°*, and solute, Δµ₂°*, and enthalpy, ΔH*, and entropy of activation, ΔS*, of viscous flow. The refractive index data have been used to calculate molar refractivity, R _D, of amino acids in aqueous tetrapropylammonium bromide solutions. It has been observed that ?_v°, B-coefficient and Δµ₂°* vary linearly with increasing number of carbon atoms in the alkyl chain of amino acids, and they were split to get contributions from the zwitterionic end groups (NH₃ ⁺, COO^-) and methylene group (CH₂) of the amino acids. The behavior of these parameters has been used to investigate the solute-solute and solute-solvent interactions as well as the effect of tetrapropylammonium cation (C₃H₇)₄N⁺ on these interactions.     

Solubility of some phenolic compounds in aqueous alkali metal nitrate solutions from (293.15 to 318.15) K

This paper is continuation of the study concerning the solubility-temperature dependence data for some phenolic compounds (PhC), contained in olive mill wastewater (OMWW), in two nitrate salts (KNO₃ and NaNO₃) aqueous solutions. The solubilities of PhC were determined in the temperature ranging from (293.15 to 318.15) K. It has been observed that the solubility, in aqueous nitrate solutions, increases with increasing temperature. Results showed that alkali metal nitrate has a salting-out effect on the solubility of PhC. The effect of the anion of the electrolyte on the solubility of PhC is observed by comparing these results with values reported in the previous papers for the effect of LiCl, NaCl and KCl. For each cation, the solubilites of the phenolic compounds are higher with nitrate anion than with chloride anion. Results were interpreted in terms of the salt hydration shells and the ability of the solute to form hydrogen-bond with water. The solubility data were accurately correlated by a semi empirical equation. The standard molar Gibbs free energies of transfer of PhC (Δ_trG^°) from pure water to aqueous solutions of the nitrate salts have been calculated from the solubility data. The decrease in solubility is correlated to the positive Δ_trG^° value which is mainly of enthalpic origin.     

Thermochemistry of the Dissolution of Dipeptides Containing DL-α-Alanine in Aqueous Solutions of Sodium Dodecyl Sulfate at 298.15 K

Enthalpies of the dissolution of DL-α-alanylglycine (AlaGly), DL-α-alanyl-DL-α-alanine (AlaAla), DL-α-alanyl-DL-α-valine (AlaVal), and DL-α-alanyl-DL-norleucine (AlaNln) in an aqueous solution of sodium dodecyl sulfate (SDS) at SDS concentration of m = 0–0.07 mol kg^?1 and temperature Т = 298.15 K are measured via calorimetry. The standard values of the enthalpy of dissolution (Δ_solH ^m ) and the transfer of dipeptides (Δ_trH ^m ) from water to aqueous SDS solutions are calculated using the experimental data. The dependences of Δ_solH ^m and Δ_trH ^m the SDS concentration at a constant concentration of dipeptide are established. Thermochemical characteristics of the transfer of AlaGly, AlaAla, AlaVal, and AlaNln in the investigated range of SDS concentrations are compared. The results are interpreted by considering ion–ion, ion–polar, and hydrophobic–hydrophobic interactions between SDS and dipeptide molecules.     

The thermochemical characteristics of solution of DL-α-alanylglycine and DL-α-alanylalanine in water-alcohol mixtures at 298.15 K

The integral enthalpies of solution of DL-α-alanylglycine and DL-α-alanylalanine in water-ethanol, water-n-propanol, and water-isopropanol mixtures were measured calorimetrically at alcohol concentrations x ₂ = 0?0.4 mole fractions. The standard enthalpies of solution (Δ_sol H°) of the peptides and their transfer (Δ_tr H°) from water into the mixed solvents were calculated. The influence of the structure and properties of the solutes and mixture composition on the enthalpy characteristics were considered. The Δ_sol H° = f(x ₂) and Δ_tr H° = f(x ₂) dependences were found to have extrema. The enthalpy coefficients of pair interactions (h _xy ) between the peptide and alcohol molecules were calculated. The coefficients were positive and increased in the series ethanol, n-propanol, isopropanol.     

The thermochemistry of solution of L-α-alanyl-L-α-alanine in water-alcohol mixtures at 298.15 K

The integral enthalpies of solution of L-α-alanyl-L-α-alanine in water-ethanol, water-n-propanol, and water-isopropanol mixtures were measured calorimetrically at alcohol concentrations x ₂ ranging from 0 to 0.4 mole fractions. The standard enthalpy of peptide solution Δ_sol H ^o and transfer Δ_tr H ^o from water into a mixed solvent were calculated. The effect of the structure and properties of peptides and mixture composition on the enthalpy characteristics is discussed. The enthalpy coefficients of pair interactions h _xy between L-α-alanyl-L-α-alanine and alcohol molecules were calculated; these coefficients were positive and increased in the series ethanol, n-propanol, isopropanol. The analysis performed allowed the differences in the thermodynamic characteristics of solution of L-α-alanyl-L-α-alanine and DL-α-alanyl-DL-α-alanine in water-alcohol mixtures to be determined.     

Possible tests for the mechanisms of ligand exchange in solids: The deaquation-anation of [Cr(NH3)5(H2O)]X3 salts

The possibility of using correlations of ΔH⁺ and ΔH, and of ΔH⁺ and ΔS⁺ to gain insight into the mechanisms of ligand-exchange reactions in solids are discussed. These correlations are tested using literature values for the deaquation-anation reactions of [Cr(NH₃)₅(H₂O)]X₃, where X^? = Cl^?, Br^?, I^? or NO^?₃. The poor agreement in the activation parameters reported in the literature precluded a meaningful test of the ΔH?ΔH^* correlation. This poor agreement suggests that these activation parameters are strongly influenced by experimental factors that have not been controlled in studies to date. nevertheless, there is a linear correlation of ΔH² and ΔS² which gives an isokinetic temperature of 367 ± 11 K. This isokinetic behavior suggests that the same mechanism is operative throughout the series.     

The investigation of the (p,ρ,T) and (ps,ρs,Ts) properties of {(1−x)CH3OH + xLiBr} for the application in absorption refrigeration machines and heat pumps

The (p,ρ,T) and (p_s,ρ_s,T_s) properties of {(1−x)CH₃OH + xLiBr} over a wide range of state parameters are reported for the first time. The experiments were carried out in a constant volume piezometer over a temperature range from 298.15 K to 398.15 K, at 0.08421, 0.13617, 0.19692, 0.23133 and 0.26891 mole fractions and from atmospheric pressure up to 60 MPa. The experimental uncertainties are ΔT=±3 mK for temperature, Δp=±5·10⁻² MPa for high pressure and Δp=±5·10⁻⁴ MPa for atmospheric pressure, Δρ=±3·10⁻² kg · m⁻³ for density. An equation of state was derived for correlation of the experimental data of the solutions.     

Effects of concentration and temperature on molar volumes of L-serine, L-isoleucine, and L-glutamine in aqueous NaCl and NaNO3 solutions

Densities of L-serine, L-isoleucine, L-glutamine in 1.5 mol kg^?1 aqueous NaCl, and NaNO₃ solutions have been measured for several molal concentrations of amino acids at temperatures from 298.15 to 323.15 K. The partial molar volumes (? _v ⁰ ) of L-serine, L-isoleucine, and L-glutamine in 1.5 mol kg^?1 aqueous NaCl/NaNO₃ solutions have been computed using density data. The transfer partial molar volumes (Δ_tr? _v ⁰ ) of L-serine, L-isoleucine, and L-glutamine from water to 1.5 mol kg^?1 aqueous NaCl/1.5 mol kg^?1 aqueous NaNO₃ solutions have been determined at 298.15 K. The trends of variation of ? _v ⁰ and Δ_tr? _v ⁰ with change in temperature have been discussed in terms of ion-ion, ion-hydrophilic, and ion-hydrophobic interactions operative in solutions.     

Measuring the enthalpies of interaction between glycine,L-cysteine,glycylglycine, and sodium dodecyl sulfate in aqueous solutions

Calorimetric measurements of enthalpies of solution Δ_sol H ^m for glycine, L-cysteine, and glycylglycine in aqueous solutions of sodium dodecyl sulfate (SDS) with concentrations of up to 0.05 mol kg^–1 are made. Standard enthalpy of solution Δ_sol H ⁰ and enthalpy of transfer Δ_tr H ⁰ of the dipeptide from water into mixed solvent are calculated. The calculated enthalpy coefficients of paired interactions of amino acids and dipeptide with SDS prove to be positive. Hydrophobic interactions between the biomolecules and SDS are found to have a major impact on the enthalpies of interaction in the three-component systems under study, within the indicated range of concentrations.