A Thermodynamic Study on the Binding of Polyethyleneglycol 1500 Stearic Acid with Lysozyme

Thermodynamics of the interaction between copolymer of Stearic acid + polyethyleneglycol 1500 mixtures, S1500, with lysozyme was investigated at pH 7.0 and 27 °C in phosphate buffer by isothermal titration calorimetry, ITC. The extended solvation model was used to reproduce the enthalpies of S1500+lysozyme interactions. The solvation parameters recovered from the extended solvation model, attributed to the structural change of lysozyme. The binding parameters found for the interaction of S1500 with lysozyme, indicate that there are 2 set of binding sites in this interaction. The observations indicated that the low S1500 content induced protein stabilization, whereas at the high S1500 concentration, much more stabilization occurred in lysozyme structure. DOI: http://dx.doi.org/10.17807/orbital.v11i7.137

Thermodynamic study on micellization of tetradecyltrimethylammonium bromide ‎surfactant in mixes methanol/ethanol/propanol +water and Ponceau 4R and Sunset ‎yellow FCF dyes using of conductometric measurement

In this work, the micellization behavior of tetradecyltrimethylammonium bromide ‎‎(TTAB) surfactant was investigated in aqueous solvent mixtures of methanol, ethanol ‎and propanol on different mass fractions (10-30%) and aqueous solution of Ponceau 4R ‎and Sunset yellow FCF dyes at concentrations (0.001-0.007mM) based on ‎conductometric technique at T=(298-313)K. The critical micelle concentration (CMC) ‎values and dissociation degrees of TTAB surfactant were determined. The obtained ‎results showed that the CMC value increases with rising of methanol and ethanol mas ‎fractions but the CMC value decreases with rising of propanol mas fractions. Also, the ‎obtained results indicated that the CMC value decreases with concentration increasing of ‎Ponceau 4R and Sunset yellow FCF dyes. In addition, thermodynamic properties such as ‎the Gibbs energy, enthalpy and entropy of micellization were calculated as a function of ‎temperature, dye concentration and alcohol mass fractions.

Activity Coefficient Measurements and Thermodynamic Modeling of (CaCl₂ + l‑Alanine + Water) System Based on Potentiometric Determination at <i>T</i> = (298.2, 303.2, and 308.2) K

In this work, the thermodynamic properties of the ternary (CaCl₂ + l-alanine + water) system, using the potentiometric method, were reported. The potentiometric measurements were performed on the galvanic cell of the type: Ag–AgCl|CaCl₂·2H₂O (<i>m</i>), l-alanine (<i>m</i>_A), H₂O|Ca–ISE, in various mixed solvent systems containing 0.0 mol·kg^–1, 0.1 mol·kg^–1, 0.2 mol·kg^–1, 0.3 mol·kg^–1, and 0.4 mol·kg^–1 of l-alanine, over total ionic strengths from 0.0100 mol·kg^–1 to 3.0000 mol·kg^–1 at <i>T</i> = (298.2, 303.2, and 308.2) K and <i>P</i> = 0.1 MPa. The Ca–ISE was prepared in our laboratory using the ionophore treated by carbon nanotubes. The Debye–Hückel extended equation, Pitzer ion interaction and PSC models were used to correlate the experimental data. The unknown parameters were evaluated and utilized to calculate the thermodynamic properties such as the mean activity coefficients, the osmotic coefficients, the solvent activity, and the excess Gibbs free energy for underinvestigated electrolyte solutions

Thermodynamic Properties Determination and Modeling of the (CaCl₂ + Ca(NO₃)₂ + l‑Glutamine + H₂O) System Using Potentiometric Measurements at <i>T</i> = (293.2, 303.2, and 313.2) K

The thermodynamic properties of the quaternary (CaCl₂ + Ca­(NO₃)₂ + l-glutamine + H₂O) system, determined using the potentiometric method, were reported. The potentiometric measurements were performed in aqueous solution containing 2.5% mass fraction of l-glutamine, over total ionic strengths from 0.0100 mol·kg^–1 to 4.0000 mol·kg^–1 at <i>T</i> = (293.2, 303.2 and 313.2) K and <i>P</i> = 0.1 MPa. Different series of the salt molal ratios <i>r</i> (<i>r</i> = <i>m</i>_CaCl₂/<i>m</i>_Ca(NO₃)₂= 1, 2.5, 5.0, 7.5, 10.0) and single salt CaCl₂ and Ca­(NO₃)₂ solution in aqueous solution containing 2.5% mass fraction of l-glutamine were used for the potentiometric measurements. The Ca-ISE was prepared in our laboratory using the ionophore treated by carbon nanotubes. The Pitzer ion interaction model was used to correlate the experimental data. The mixed ionic interaction parameters (θ_ClNO₃ and ψ_CaClNO₃) were evaluated according to Pitzer graphical method. The mixing parameters obtained were used to calculate the values of the mean activity coefficients of Ca­(NO₃)₂, the osmotic coefficients, the solvent activity, the excess Gibbs free energies, the excess enthalpy, excess heat capacity, and the excess entropy for the whole series of the studied mixed electrolyte system. There is a good consistency between the experimental results and Pitzer model

A Thermodynamic Study on the Binding of Polyethyleneglycol 1500 Stearic Acid with Lysozyme

Thermodynamics of the interaction between copolymer of Stearic acid + polyethyleneglycol 1500 mixtures, S1500, with lysozyme was investigated at pH 7.0 and 27 °C in phosphate buffer by isothermal titration calorimetry, ITC. The extended solvation model was used to reproduce the enthalpies of S1500+lysozyme interactions. The solvation parameters recovered from the extended solvation model, attributed to the structural change of lysozyme. The binding parameters found for the interaction of S1500 with lysozyme, indicate that there are 2 set of binding sites in this interaction. The observations indicated that the low S1500 content induced protein stabilization, whereas at the high S1500 concentration, much more stabilization occurred in lysozyme structure. DOI: http://dx.doi.org/10.17807/orbital.v11i7.1373 </p