Catalytic and Thermodynamic Characterization of Endoglucanase (CMCase) from <Emphasis Type="Italic">Aspergillus oryzae</Emphasis> cmc-1

Monomeric extracellular endoglucanase (25 kDa) of transgenic koji (Aspergillus oryzae cmc-1) produced under submerged growth condition (7.5 U mg⁻¹ protein) was purified to homogeneity level by ammonium sulfate precipitation and various column chromatography on fast protein liquid chromatography system. Activation energy for carboxymethylcellulose (CMC) hydrolysis was 3.32 kJ mol⁻¹ at optimum temperature (55 °C), and its temperature quotient (Q ₁₀) was 1.0. The enzyme was stable over a pH range of 4.1–5.3 and gave maximum activity at pH 4.4. V _max for CMC hydrolysis was 854 U mg⁻¹ protein and K _m was 20 mg CMC ml⁻¹. The turnover (k _cat) was 356 s⁻¹. The pK _a1 and pK _a2 of ionisable groups of active site controlling V _max were 3.9 and 6.25, respectively. Thermodynamic parameters for CMC hydrolysis were as follows: ΔH* = 0.59 kJ mol⁻¹, ΔG* = 64.57 kJ mol⁻¹ and ΔS* = −195.05 J mol⁻¹ K⁻¹, respectively. Activation energy for irreversible inactivation ‘E _a(d)’ of the endoglucanase was 378 kJ mol⁻¹, whereas enthalpy (ΔH*), Gibbs free energy (ΔG*) and entropy (ΔS*) of activation at 44 °C were 375.36 kJ mol⁻¹, 111.36 kJ mol⁻¹ and 833.06 J mol⁻¹ K⁻¹, respectively.     

Study of catalase immobilized on a silicate matrix for non-aqueous biocatalysis

Catalytic activity of catalase (CAT) immobilized on a modified silicate matrix to mediate decomposition of meta-chloroperoxibenzoic acid (3-CPBA) in acetonitrile has been investigated by means of quantitative UV-spectrophotometry. Under the selected experimental conditions, the kinetic parameters: the apparent Michaelis constat (K _M ), the apparent maximum rate of enzymatic reaction (V _max ^app ), the first order specific rate constants (k _sp ), the energy of activation (E _a ) and the pre-exponential factor of the Arrhenius equation (Z₀) were calculated. Conclusions regarding the rate-limiting step of the overall catalytic process were drawn from the calculated values of the Gibbs energy of activation ΔG^*, the enthalpy of activation ΔH^*, and the entropy of activation ΔS^*.     

Excess molar volumes,viscosity, refractive index,and Gibbs energy of activation of binary biodiesel + benzene,and biodiesel + toluene mixtures at 298.15 and 303.15 K

Excess molar volumes (V ^E), viscosities, refractive index, and Gibbs energies were evaluated for binary biodiesel + benzene and toluene mixtures at 298.15 and 303.15 K. The excess molar volumes V ^E were determined from density, while the excess Gibbs free energy of activation G*^E was calculated from viscosity deviation Δη. The excess molar volume (V ^E), viscosity deviation (Δη), and excess Gibbs energy of activation (G*^E) were fitted to the Redlich-Kister polynomial equation to derive binary coefficients and estimate the standard deviations between the experimental data and calculation results. All mixtures showed positive V ^E values obviously caused by increased physical interactions between biodiesel and the organic solvents.     

Equilibrium and kinetics study of Gd(III) and U(VI) adsorption from aqueous solutions by modified Sorrel’s cement

Modified Sorrel’s cement was prepared by the addition of ferric chloride. The modified cement (MF5) was analyzed and characterized by different methods. Adsorption of Gd(III) and U(VI) ions in carbonate solution has been studied separately as a function of pH, contact time, adsorbent weight, carbonate concentration, concentration of Gd(III) and U(VI) and temperature. From equilibrium data obtained, the values of Δ H, Δ S and Δ G were found to equal −30.9 kJ ⋅ mol⁻¹, −85.4 J ⋅ mol⁻¹ ⋅,K⁻¹, and −5.4 KJ ⋅ mol⁻¹, respectively, for Gd(III) and 18.9 kJ ⋅ mol⁻¹, 67.8 J ⋅ mol⁻¹ K⁻¹ and −1.3 KJ ⋅ mol⁻¹, respectively, for U(VI). The equilibrium data obtained have been found to fit both Langmuir and Freundlich adsorption isotherms. The batch kinetic of Gd(III) and U(VI) on modified Sorrel’s cement (MF5) with the thermodynamic parameters from carbonate solution were studied to explain the mechanistic aspects of the adsorption process. Several kinetic models were used to test the experimental rate data and to examine the controlling mechanism of the adsorption process. Various parameters such as effective diffusion coefficient and activation energy of activation were evaluated. The adsorption of Gd(III) and U(VI) on the MF5 adsorbent follows first-order reversible kinetics. The forward and backward constants for adsorption, k ₁and k ₂ have been calculated at different temperatures between 10 and 60^∘C. Form kinetic study, the values of Δ H ^* and Δ S ^* were calculated for Gd(III) and U(VI) at 25^∘C. It is found that Δ H ^* equals −14.8 kJmol⁻¹ and 7.2 kJmol⁻¹ for Gd(III) and U(VI), respectively, while Δ S ^* were found equal −95.7 Jmol⁻¹K⁻¹ and −70.5 Jmol⁻¹K⁻¹ for Gd(III) and U(VI), respectively. The study showed that the pore diffusion is the rate limiting for Gd(III) and (VI).     

Purification and Characterization of Chitinase from <Emphasis Type="BoldItalic">Paenibacillus</Emphasis> sp. D1

A 56.56-kDa extracellular chitinase from Paenibacillus sp. D1 was purified to 52.3-fold by ion exchange chromatography using SP Sepharose. Maximum enzyme activity was recorded at pH 5.0 and 50 °C. MALDI-LC-MS/MS analysis identified the purified enzyme as chitinase with 60% similarity to chitinase Chi55 of Paenibacillus ehimensis. The activation energy (E _a) for chitin hydrolysis and temperature quotient (Q ₁₀) at optimum temperature was found to be 19.14 kJ/mol and 1.25, respectively. Determination of kinetic constants k _m, V _max, k _cat, and k _cat/k _m and thermodynamic parameters ΔH*, ΔS*, ΔG*, ΔG*_E–S, and ΔG*_E–T revealed high affinity of the enzyme for chitin. The enzyme exhibited higher stability in presence of commonly used protectant fungicides Captan, Carbendazim, and Mancozeb compared to control as reflected from the t _1/2 values suggesting its applicability in integrated pest management for control of soil-borne fungal phytopathogens. The order of stability of chitinase in presence of fungicides at 80 °C as revealed from t _1/2 values and thermodynamic parameters E _a(d) (activation energy for irreversible deactivation), ΔH*, ΔG*, and ΔS* was: Captan > Carbendazim > Mancozeb > control. The present study is the first report on thermodynamic and kinetic characterization of chitinase from Paenibacillus sp. D1.     

Volumetric and Transport Properties of Ternary Mixtures Containing 1-Butanol or 1-Pentanol,Triethylamine and Cyclohexane at 303.15 K: Experimental Data,Correlation and Prediction by the ERAS Model

The excess molar volumes, V _m^E, viscosity deviations, Δη, and excess Gibbs energies of activation, ΔG ^*E, of viscous flow have been investigated from density and viscosity measurements for two ternary mixtures, 1-butanol + triethylamine + cyclohexane and 1-pentanol + triethylamine + cyclohexane, and corresponding binaries at 303.15 K and atmospheric pressure over the entire range of composition. The empirical equations due to Redlich-Kister, Kohler, Rastogi et al., Jacob-Fitzner, Tsao-Smith, Lark et al., Heric-Brewer, and Singh et al. have been employed to correlate V _m^E, Δη and ΔG ^*E of the ternary mixtures with their corresponding binary parameters. The results are discussed in terms of the molecular interactions between the components of the mixture. Further, the Extended Real Associated Solution, ERAS, model has been applied to V _m^E for the present binary and ternary mixtures, and the results are compared with experimental data.     

A model developed for acid dissolution thermodynamics of a Turkish bentonite

A model was proposed to calculate some thermodynamic parameters for the acid dissolution process of a bentonite containing a calcium-rich smectite as clay mineral along with quartz, opal and feldspar as impurities. The bentonite sample was treated with H₂SO₄ by applying dry method in the temperature range 50–150°C for 24 h. The acid content in the dry bentonite-sulphuric acid mixture was 45 mass%. The total content (x) of Al₂O₃, Fe₂O₃ and MgO remained in the undissolved sample after treatment was taken as an equilibrium parameter. An apparent equilibrium constant, K _a, was calculated for each temperature by assuming K _a=(x _m−x)/x where x _m is the total oxide content of the natural bentonite. Also, an apparent change in Gibbs free energy, ΔG _a^o, was calculated for each temperature by using the K _a value. The graphs of lnK _a vs. 1/T and ΔG _a^o vs. T were drawn and then the real change in both the enthalpy, ΔH ^o and the entropy, ΔS ^o, values were calculated from the slopes of the straight lines, respectively. Inversely, real ΔG ^o and K values were calculated from the real ΔH ^o and ΔS ^o values through ΔG ^o = −RT ln K = ΔH ^o − TΔS ^o equation. The best ΔH ^o and ΔS ^o fittings to this relation were found to be 65687 J mol⁻¹ and 164 J mol⁻¹K⁻¹, respectively.     

Adsorption of uranium(VI) onto <Emphasis Type="Italic">Ulva sp.</Emphasis>-sepiolite composite

Ulva sp. and sepiolite were used to prepare composite adsorbent. The adsorption of uranium(VI) from aqueous solutions onto Ulva sp.-sepiolite has been studied by using a batch adsorber. The parameters that affect the uranium(VI) adsorption, such as solution pH, initial uranium(VI) concentration, and temperature, have been investigated and the optimum conditions determined. The adsorption patterns of uranium on the composite adsorbent followed the Freundlich and Dubinin-Radushkevich (D-R) isotherms. The Freundlich, Langmuir, and Dubinin-Radushkevich (D-R) models have been applied and the data correlate well with Freundlich model. The sorption is physical in nature (sorption energy, E = 4.01 kJ/mol). The thermodynamic parameters such as variation of enthalpy ΔH, variation of entropy ΔS and variation of Gibbs free energy ΔG were calculated from the slope and intercept of lnK _d vs. 1/T plots. Thermodynamic parameters (ΔH _ads = −22.17 kJ/mol, ΔS _ads = −17.47 J/mol·K, ΔG ^o _ads (298.15 K) = −16.96 kJ/mol) show the exothermic heat of adsorption and the feasibility of the process. The results suggested that the Ulva sp-sepiolite composite adsorbent is suitable as a sorbent material for recovery and biosorption/adsorption of uranium ions from aqueous solutions.     

Molecular modeling of hydration properties of hydrophobic ions Li<Superscript>+</Superscript>@C<Subscript>60</Subscript> and K<Superscript>+</Superscript>@C<Subscript>60</Subscript>

The Gibbs free energies of solvation (ΔG _s) and the electronic structures of endohedral metallofullerenes M⁺@C₆₀ (M⁺= Li⁺, K⁺) were calculated within the framework of the density functional theory and the polarizable continuum model. In water environment, the equilibrium position of K⁺ is at the center of the fullerene cavity whereas that of Li⁺ is shifted by 0.14 nm toward the fullerene cage. The Li⁺ cation is stabilized by interactions with both the fullerene and solvent. The equilibrium structures of both endohedral metallofullerenes are characterized by very close ΔG _s values. In particular, the calculated ΔG _s values for K⁺@C₆₀ are in the range from −124 to −149 kJ mol⁻¹ depending on the basis set and on the type of the density functional. Molecular dynamics simulations (TIP3P H₂O, OPLS force field, water sphere of radius 1.9 nm) showed that the radial distribution functions of water density around C₆₀ and M⁺@C₆₀ are very similar, whereas orientations of water dipoles around the endohedral metallofullerenes resemble the hydration pattern of isolated metal ions.     

Effect of Buffer Species on the Complexation of Basic Drug Terfenadine with β-Cyclodextrin

The complexation of terfenadine (Terf) with β-cyclodextrin (β-CD) in solution and solid state has been investigated by phase solubility diagram (PSD), differential scanning calorimetry (DSC), powder X-ray diffractometry (PXD) and proton nuclear magnetic resonance (¹H-NMR). The PSD results indicated that the salt saturation with the buffer counter ion (citrate⁻², H₂PO₄⁻¹ and Cl⁻¹ ions) of Terf (pK _a = 9.5) and the hydrophobic effect play in tandem to increase the value of the complex formation constant (K₁₁) measured at different conditions of pH, ionic strength, buffer type and buffer concentration. The correlation of the free energy of complex formation (ΔG₁₁) with the free energy of inherent solubility of Terf (ΔG_So) obtained by changing the pH, ionic strength and buffer concentration was used to measure the contribution of the hydrophobic effect (desolvation) to complex formation. The hydrophobic effect was found to constitute 57.8% of the driving force for complex stability, while other factors including specific interactions contribute −13.4 kJ/mol. ¹H-NMR spectra of Terf–citrate and Terf–HCl salts gave identical chemical shift displacements (ΔΔ) upon complexation, thus indicating that the counter anions are positioned somewhere outside of the β-CD cavity. DSC, XRPD and ¹H-NMR proved the formation of solid Terf/acid/β-CD ternary complexes.     

Evaluation of kinetic parameters of uranyl acetate complexes in ethanolic solution by cyclic voltammetry

The complexation of uranyl ion with acetate ions was investigated in 20% ethanolic solution by using cyclic voltammetry. The uranium formed 1:1 and 1:2 complexes with acetate ions. The values of log β₁ and log β₂ for uranyl acetate complexes were 2.05 ± 0.08 and 5.25 ± 0.06 respectively. The diffusion coefficient and heterogeneous rate constants for the reduction of uranyl ion at hanging mercury drop electrode in 20% ethanolic solution of acetate ions were 0.43 × 10⁻⁵ cm² s⁻¹ and 2.26 × 10⁻³ cm s⁻¹, respectively. Thermodynamic parameters were also evaluated by finding the effect of temperature on the heterogeneous rate constants. The values of ΔH ^*, ΔS ^* and \Updelta G₂₉₈^* \Updelta G_{298}^{*} were 2.52 kJ mol⁻¹, −43.8 J mol⁻¹ K⁻¹ and 15.57 kJ mol⁻¹. The positive values of ΔH ^* and \Updelta G₂₉₈^* \Updelta G_{298}^{*} indicated that electrochemical reduction of uranyl ions in ethanolic solution of acetate ions is an endothermic and non-spontaneous process.     

An indirect thermodynamic model developed for initial stage sintering of an alumina compacts by using porosity measurements

The specific micro- and mesopore volumes (V) of alumina compacts fired between 900 and 1250 °C for 2 h were determined from nitrogen adsorption/desorption data. The V value was taken as a sintering equilibrium parameter. An arbitrary sintering equilibrium constant (K _a) was estimated for each firing temperature by assuming K _a = (V _i − V)/V, where V _i is the largest value at 900 °C before sintering. Also, an arbitrary Gibbs energy (ΔG _a °) of sintering was calculated for each temperature using the K _a value. The graph of ln K _a versus 1/T and ΔG _a ° versus T were plotted, and the real enthalpy (ΔH°) and the real entropy (ΔS°) of sintering were calculated from the slopes of the obtained straight lines, respectively. On the contrary, real ΔG° and K values were calculated using the real ΔH° and ΔS° values in the ΔG° = −RT lnK = 165814 − 124.7T relation in SI units.     

Charge-transfer interactions between nucleophilic compounds and chromatographic packings containing chemically bonded Cu(II) complexes

Summary Results are presented of studies of packings containing copper (II) acetylacetonate (acac), hexafluoroacetylacetonate (hfac), and chloride, chemically bonded via β-dik-etonate groups. The retention parameters retention factor (k) specific retention volume (V _g), and molecular retention index (M _e) were measured and used to calculate the thermodynamic parameters free energy of adsorption (ΔG _a) heat of adsorption (−ΔH _a), and entropy of adsorption (ΔS _a). These parameters enable, characterization of specific interactions between aromatic and cyclic hydrocarbons, ethers and thioethers and metal complexes chemically bonded, to a silica surface.     

Thermal behavior of 3,4,5-triamino-1,2,4-triazole dinitramide

The thermal decomposition behavior of 3,4,5-triamino-1,2,4-triazole dinitramide was measured using a C-500 type Calvet microcalorimeter at four different temperatures under atmospheric pressure. The apparent activation energy and pre-exponential factor of the exothermic decomposition reaction are 165.57 kJ mol⁻¹ and 10^18.04 s⁻¹, respectively. The critical temperature of thermal explosion is 431.71 K. The entropy of activation (ΔS ^≠), enthalpy of activation (ΔH ^≠), and free energy of activation (ΔG ^≠) are 97.19 J mol⁻¹ K⁻¹, 161.90 kJ mol⁻¹, and 118.98 kJ mol⁻¹, respectively. The self-accelerating decomposition temperature (T _SADT) is 422.28 K. The specific heat capacity of 3,4,5-triamino-1,2,4-triazole dinitramide was determined with a micro-DSC method and a theoretical calculation method. Specific heat capacity (J g⁻¹ K⁻¹) equation is C _p = 0.252 + 3.131 × 10⁻³  T (283.1 K < T < 353.2 K). The molar heat capacity of 3,4,5-triamino-1,2,4-triazole dinitramide is 264.52 J mol⁻¹ K⁻¹ at 298.15 K. The adiabatic time-to-explosion of 3,4,5-triamino-1,2,4-triazole dinitramide is calculated to be a certain value between 123.36 and 128.56 s.     

A theoretical study of explosive sensitizers

Quantum chemical calculations at the HF/6-31G^* and B3LYP/6-31G^* levels have been performed on five explosive sensitizers, ethyl nitrate (EN), n-propyl nitrate (NPN), isopropyl nitrate (IPN), 2-ethylhexyl nitrate (EHN) and tetraethylene glycol dinitrate (TEGDN). Theoretical study has made a detailed molecular-level investigation of the title compounds. Based on the Mulliken populations and bond lengths, the fission of the O₂–N₃ can be acceptable reasonably. Charge distribution analysis indicates that the five nitrates produce NO₂ gas during the dissociation of the O₂–N₃ weak bond. We also order the relative thermal stability of five nitrates on the basis of frontier orbital energy (E _HOMO, E _LUMO) and energy gap (ΔE = E _HOMO − E _LUMO).     

Production of low sulfur diesel fuel via adsorption: an equilibrium and kinetic study on the adsorption of dibenzothiophene onto NaY zeolite

The adsorption of dibenzothiophene (DBT) in hexadecane onto NaY zeolite has been studied by performing equilibrium and kinetic adsorption experiments. The influence of several variables such as contact time, initial concentration of DBT and temperature on the adsorption has been investigated. The results show that the isothermal equilibrium can be represented by the Langmuir equation. The maximum adsorption capacity at different temperatures and the corresponding Langmuir constant (K _L ) have been deduced. The thermodynamic parameters (ΔG ⁰,ΔH ⁰,ΔS ⁰) for the adsorption of DBT have also been calculated from the temperature dependence of K _L using the van’t Hoff equation. The value of ΔH ⁰,ΔS ⁰ are found to be −30.3 kJ mol⁻¹ and −33.2 J mol⁻¹ K⁻¹ respectively. The adsorption is spontaneous and exothermic. The kinetics for the adsorption process can be described by either the Langmuir model or a pseudo-second-order model. It is found that the adsorption capacity and the initial rate of adsorption are dependent on contact time, temperature and the initial DBT concentration. The low apparent activation energy (12.4 kJ mol⁻¹) indicates that adsorption has a low potential barrier suggesting a mass transfer controlled process. In addition, the competitive adsorption between DBT, naphthalene and quinoline on NaY was also investigated.     

Adsorption syntax of Au(III) on unloaded polyurethane foam

The nature of adsorption behavior of Au(III) on polyurethane (PUR) foam was studied in 0.2M HCl aqueous solution. The effect of shaking time and amount of adsorbent were optimized for 3.16·10⁻⁵M solution of Au(III) in 0.2M HCl. The classical Freundlich and Langmuir adsorption isotherms have been employed successfully. The Freundlich parameters 1/n and adsorption capacityK are 0.488±0.016 and (1.40±0.22)·10⁻² mol·g⁻¹, respectively. The Langmuir constants of saturation capacityM and binding energyb are (1.66±0.08)·10⁻⁴mol·g⁻¹ and 40294±2947 l·g⁻¹, respectively, indicating the monolayer chemical sorption. The mean free energy (E) of adsorption of Au(III) on PUR foam has been evaluated using D-R isotherm and found to be 11.5±0.16 kJ·mol⁻¹ reflecting the ion exchange type of chemical adsorption. The effect of temperature on the adsorption has also been studied. the isosteric heat of adsorption was found to be 44.03±1.66 kJ·mol⁻¹. The thermodynamic parameters of ΔG, ΔH, ΔS and equilibrium constantK _c have been calculated. The negative values of ΔG, ΔH and ΔS support that the adsorption of Au(III) on PUR foam is spontaneous, exothermic and of ion exchange chemisorption. The nature of the Au(III) species sorbed on PUR foam have been discussed.     

Ion-pair formation in the outer-sphere electron transfer reactions between tris-(1, 10) phenanthroline iron(II) and the halopentacyanocobaltate(III) complexes in aqueous acidic solutions

The kinetics of the reactions between Fe(phen) ₃ ²⁺ [phen = tris–(1,10) phenanthroline] and Co(CN)₅X³⁻ (X = Cl, Br or I) have been investigated in aqueous acidic solutions at I = 0.1 mol dm⁻³ (NaCl/HCl). The reactions were carried out at a fixed acid concentration ([H⁺] = 0.01 mol dm⁻³) and the second-order rate constants for the reactions at 25 °C were within the range of (0.151–1.117) dm³ mol⁻¹ s⁻¹. Ion-pair constants K _ip for these reactions, taking into consideration the protonation of the cobalt complexes, were 5.19 × 10⁴, 3.00 × 10² and 4.02 × 10⁴ mol⁻¹ dm⁻³ for X = Cl, Br and I, respectively. Activation parameters measured for these systems were as follows: ΔH* (kJ K⁻¹ mol⁻¹) = 94.3 ± 0.6, 97.3 ± 1.0 and 109.1 ± 0.4; ΔS* (J K⁻¹) = 69.1 ± 1.9, 74.9 ± 3.2 and 112.3 ± 1.3; ΔG* (kJ) = 73.7 ± 0.6, 75.0 ± 1.0 and 75.7 ± 0.4; E _a (kJ) = 96.9 ± 0.3, 99.8 ± 0.4, and 122.9 ± 0.3; A (dm³ mol⁻¹ s⁻¹) = (7.079 ± 0.035) × 10¹⁶, (1.413 ± 0.011) × 10¹⁷, and (9.772 ± 0.027) × 10²⁰ for X = Cl, Br, and I respectively. An outer – sphere mechanism is proposed for all the reactions.     

Kinetics and thermal stability of two peroxidase isozymes from Eupatorium odoratum

The Eupatorium odoratum leaf peroxidase exists as at least seven distinct isozymes (three cationic, three anionic, and one neutral). These isozymes were identified and separated by preparative iso-electric focusing. Thermal stability, including the activation enthalpy (ΔH ^*), free energy of inactivation (ΔG ^*) and activation entropy (ΔS ^*), and kinetic studies of two isozymes, one having a pI of 5.0 (E5) and another one having a pI of 7.0 (E7) with mol mass of 43 and 50 kD, respectively, were studied in detail. Of the molecular weight of E5 and E7, 25 and 32% correspond to the carbohydrate content of the isozymes. Optimal pH was in the acidic range of 3.6–3.8 for E5 and 3.8 for E7 with the oxidation of ABTS. E7 and E5 showed activation energy for inactivation, 194.8 and 145.4 kJ/mol, respectively. Both the isozymes showed distinct substrate specificity. The catalytic specificity constant for E5 and E7 were 112×10⁵ and 124×10⁵/s·M, respectively, when 2,2′-azino-bis-(3-ethylbenz-thiazoline-6 sulfonic acid) was used as the substrate. Maximum affinity (i.e., lowest K _m value) to H₂O₂ was shown by E5 and E7 along with Pyrogallol and was 0.02 and 0.05/s·M, respectively.     

Thermodynamics of mixed-ligand complexation of mercury(II) ethylenediaminetetraacetate with histidine and lysine in aqueous solution

The formation of mixed-ligand complexes HgEdtaIm²⁻, HgEdtaL³⁻, HgEdtaHL²⁻, and (HgEdta)₂L⁵⁻ (L is histidine, lysine; Im is imidazole) was studied by calorimetry, pH-metry, and NMR spectroscopy. The thermodynamic parameters (logK, ΔrG ⁰, ΔrH, Δr _S) for the reactions of complex formation at 298.15 K and ion strength of 0.5 (KNO₃) were determined. The most likely coordination mode for the complexone and amino acid in the mixed complexes was identified.