Hoff Equation Research Articles

Determination of dissociation constants of protein ligands by thermal shift assay

The thermal shift assay (TSA) is a powerful tool used to detect molecular interactions between proteins and ligands. Using temperature as a physical denaturant and an extrinsic fluorescent dye, the TSA tracks protein unfolding. This method precisely determines the midpoint of the unfolding transition (Tm), which can shift upon the addition of a ligand. Though experimental protocols have been well developed, the thermal shift assay data traditionally yielded qualitative results. Quantitative methods for Kd determination relied either on empirical and inaccurate usage of Tm or on isothermal approaches, which do not take full advantage of the melting point precision provided by the TSA. We present a new analysis method based on a model that relies on the equilibrium system between the native and molten globule state of the protein using the van't Hoff equation. We propose the Kd can be determined by plotting Tm values versus the logarithm of ligand concentrations and fitting the data to an equation we derived. After testing this procedure with the monomeric maltose-binding protein and an allosterically regulated homotetrameric enzyme (ADP-glucose pyrophosphorylase), we observed that binding results correlated very well with previously established parameters. We demonstrate how this method could potentially offer a broad applicability to a wide range of protein classes and the ability to detect both active and allosteric site binding compounds.

Solubility of Sulfamethazine in the Binary Mixture of Acetonitrile + Methanol from 278.15 to 318.15 K: Measurement, Dissolution Thermodynamics, Preferential Solvation, and Correlation

Solubility of sulfamethazine (SMT) in acetonitrile (MeCN) + methanol (MeOH) cosolvents was determined at nine temperatures between 278.15 and 318.15 K. From the solubility data expressed in molar fraction, the thermodynamic functions of solution, transfer and mixing were calculated using the Gibbs and van ’t Hoff equations; on the other hand, the solubility data were modeled according to the Wilson models and NRTL. The solubility of SMT is thermo-dependent and is influenced by the solubility parameter of the cosolvent mixtures. In this case, the maximum solubility was achieved in the cosolvent mixture at 318.15 K and the minimum in pure MeOH at 278.15 K. According to the thermodynamic functions, the SMT solution process is endothermic in addition to being favored by the entropic factor, and as for the preferential solvation parameter, SMT tends to be preferentially solvated by MeOH in all cosolvent systems; however, , so the results are not conclusive. Finally, according to mean relative deviations (MRD%), the two models could be very useful tools for calculating the solubility of SMT in cosolvent mixtures and temperatures different from those reported in this research.

Influence of ionization and position of substituents on the solubility, solvation and transfer processes: A thermodynamic study of hydroxybenzamide and acetamidobenzoic acid isomers

Solubility of i-hydroxybenzamides and i-acetamidobenzoic acids (i = 2, 3, 4) in buffer solutions (pH 2.0 and 7.4), 1-octanol and n-hexane were measured by the isothermal saturation method in the temperature range (293.15–315.15 K). The following order of the solubility was revealed (in mole fraction): 1-octanol > buffer pH 7.4 > buffer pH 2.0 > n-hexane. The solubility was correlated by the van’t Hoff and Apelblat equations. The best result was achieved with the van’t Hoff model. HYBOT descriptors for biologically active compounds have been calculated and the impact of the donor–acceptor capacity of the molecules on drug solubility has been studied. The thermodynamic parameters of solubility, solvation and transfer processes were calculated and discussed in view of solute–solvent interactions. A diagram approach was used to analyze the enthalpy and entropy contributions to the Gibbs energy of transfer processes from n-hexane to solvents and from buffer solutions to 1-octanol for the substances studied.

Highly-efficient nitrogen self-doped biochar for versatile dyes’ removal prepared from soybean cake via a simple dual-templating approach and associated thermodynamics

Biochar has very low adsorption capacity to anionic dyes due to negative charge on the surface. Herein, a dual-templating strategy by mild activators (K2C2O4·H2O and CaCO3) was applied for synthesis of soybean cake nitrogen self-doped biochar (NSB) to enhance the adsorption capacity for dyes. The results of element analysis showed NSB had N contents of 3.51%. Its specific surface area was 2413.00 m2 g−1 and maximum adsorption amount of Rhodamine B and Congo Red reached up to 839.97 mg g−1 and 882.64 mg g−1, respectively. The NSB retained high adsorption capacity after 5 cycles. By linear fitting of full Van't Hoff equation, lower enthalpy value shown in Congo Red adsorption in comparison with Rhodamine B adsorption, indicated the efficient anionic dye removal by NSB. Negative heat capacity change value indicated water molecules adsorbed on the NSB surface were replaced by dyes molecules. This paper provides a framework to prepare excellent NSB for the efficient removal of dyes from wastewater and shed lights on the mechanism of how NSB work for respective cationic and anionic dye from thermodynamics.

Solid-liquid phase equilibrium, Hansen solubility parameters and thermodynamic behavior of Arbidol hydrochloride monohydrate in eleven mono-solvents

The experimental mole-fraction solubility of Arbidol hydrochloride monohydrate (AHM) in eleven mono-solvents (water, methanol, ethanol, n-propanol, isopropanol, n-butanol, N,N-Dimethylformamide (DMF), n-Methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), acetone and ethyl acetate) at varied temperatures (from 293.15 K to 333.15 K at 5 K intervals) was determined under an atmosphere pressure of 0.101 MPa, which indicated that the solubility of AHM increases with the temperature arising. Furthermore, the solubility sequence of AHM at 298.15 K is: methanol (0.04422) > NMP (0.03516) > DMF (0.02437) > ethanol (0.01161) > n-propanol (0.006280) > n-butanol (0.004411) > isopropanol (0.001611) > THF (0.0004917) > acetone (0.0002516) > ethyl acetate (0.0001007) > water (0.00007344). The solubility behavior and the solute–solventinteraction of AHM in each selected mono-solvent had been explored by the Hansen solubility parameters (HSPs) and solvents polarity. Based on linear solvation energy relationships concept, the KAT-LSER model was applied to investigate the solvent effects. Experimental solubility of AHM was modelled by using four well-known SLE models, namely two empirical models (modified Apelblat model and λh model) and two activity coefficient models (NRTL model and UNIQUAC model), which indicated that four chosen SLE models can all give a satisfactory correlation solubility of AHM with the measured solubility data, while the modified Apelblat model shows the best correlation with experimental data in all investigated mono-solvents. In addition, the solution thermodynamic properties (ΔdisGo, ΔdisHo and ΔdisSo) of AHM in the selected mono-solvents were calculated by van’t Hoff equation. The ascending order of ΔdisGo is exactly in the reverse order of the molar solubility of AHM, implying less the value of ΔdisGo, more soluble in that solvent. The minimum ΔdisHo and ΔdisSo were found to be 16.04 kJ∙mol−1 in NMP and 25.83 J∙K−1∙mol−1 in NMP, respectively, while the minimum value of ζH is 60%, indicating that the dissolution process of AHM in the measured mono-solvents was endothermic and entropy-driven.

Thermodynamic analysis of solubility, distribution and solvation of antifungal miconazole in relevant pharmaceutical media

In this work, solubility of antifungal drug miconazole in pharmaceutically relevant solvents were measured by the shake-flask method in the temperature range between 293.15 and 313.15 K. The solubility of compound in selected solvents increases in the following order: buffer pH 7.4, buffer pH 2.0, hexane, 1-octanol. The influence of protolytic properties of the drug on the solubility in aqueous media of different acidity was studied. It is shown that the modified Apelblat equation give better correlation results with the experimental data than Hoff equation and Two-Suffix Margules model. The Hansen solubility parameters were employed to investigation the miscibility of compound with all of tested solvents. The calculation of the thermodynamic functions of drug solubility and solvation in the selected solvents was performed. The relative contributions of sublimation and solvation to Gibbs energy of solubility for the compound in used solvents was evaluated. The excess Gibbs energy and the activity coefficients of miconazole were also calculated. The temperature dependence of the partition coefficients of the compound studied in the 1-octanol/buffer pH 7.4 system was determined and thermodynamic quantities for the transfer of this drug from water phase to organic one were obtained.

Solubility study of naproxen in the binary mixture of ethanol and ethylene glycol at different temperatures

Solubility and thermodynamic properties of naproxen in the binary mixtures of ethanol and ethylene glycol were determined by shake-flask method followed by a spectrophotometric method in the temperature range of 293.2–33.2.2 K. The acquired solubility values of naproxen are correlated by using some linear and non-linear solubility models such as the van’t Hoff, the MRS, the Jouyban-Acree, the Jouyban-Acree-van’t Hoff, the modified Wilson and the λh models. The accuracy of each used model is tested by the mean relative deviation of the back-calculated data. In addition, density values of saturated mixtures are also determined and represented by the Jouyban-Acree model at defined temperatures. Moreover, the apparent thermodynamic properties of naproxen are calculated based on van't Hoff and Gibbs equations.

Measurement, correlation of solubility and thermodynamic properties analysis of 5,5′-bis(2,4,6-trinitrophenyl)-2,2′-bis(1,3,4-oxadiazole) in different mono solvents

In this paper, the solubility of 5,5′-bis(2,4,6-trinitrophenyl)-2,2′-bis(1,3,4-oxadiazole) (TKX-55) in methanol, ethanol, 1-propanol, 2-propanol, formic acid, acetic acid, propionic acid, acetonitrile, ethyl acetate, tetrahydrofuran, nitromethane, 1,2-dichloroethane, benzene and 1,4-dioxane was determined at T = (293.15–333.15) K under atmospheric pressure (P = 0.1 MPa) by a gravimetric method. The results showed that the solubility increases with rise of temperature in all selected solvents. Additionally, the solvent effect on TKX-55 solubility was investigated with Kamlet-Taft parameters. Moreover, Hansen solubility parameter was used for explaining the solubility order of TKX-55 in selected solvents, the consequences showed that solubility order of TKX-55 resulted from the comprehensive function of several solubility parameters. The solubility parameter of Δδt between TKX-55 and solvents reached from 0.17 MPa0.5 to 8.68 MPa0.5. The interaction energy (Einter) between TKX-55 and selected solvents was calculated by molecular simulation to explain the solubility behavior. Activity coefficient was to access the solute-solvent molecular interactions. Besides, the solubility values were correlated by the modified Apelblat equation, λh equation, the polynomial empirical equation, and ideal equation, and the results showed that all models can give a satisfactory correlation. The average root-mean-square deviation (106RMSD) values were 14.57, 33.08, 8.523 and 30.29, respectively. On the basis of the van’t Hoff and Gibbs equations, the thermodynamic properties exhibited by TKX-55 (i.e., standard dissolution enthalpy (ΔdisHo), standard dissolution entropy (ΔdisSo) and standard dissolution Gibbs free energy (ΔdisGo)) in the selected solvents were characterized and then discussed from the experiment data. As revealed from the result, TKX-55 in solvents selected showed a non-spontaneous process. The excess enthalpy of solution was estimated on the basis of λh equation. And solid-liquid surface tension (γ) and surface entropy factor (f) of TKX-55 were estimated by using the experimental solubility data. Furthermore, the experimental solubility values, model parameters, and thermodynamic properties of TKX-55 in different pure solvents will provide the necessary support for its preparation, crystallization process, and further theoretical studies.

Olive oil-based quercetin nanoemulsion (QuNE)’s interactions with human serum proteins (HSA and HTF) and its anticancer activity

The current study produced Quercetin nanoemulsions (QuNEs) for the purpose of improving Quercetin solubility in an aqueous polar condition and to analyze QuNE-protein formation (QuNE-human serum albumin (HSA) and QuNE-holo-transferrin (HTF)). QuNE was produced by utilizing an ultrasound-based emulsification method and was characterized by DLS, TEM, and SEM. Its interaction with HSA and HTF proteins was studied by analyzing the results of FRET and RLS spectroscopy, Stern-Volmer plotting, the Van't Hoff equation, CD spectroscopy, and molecular docking methods. Finally, QuNE's cytotoxic impact, cell death type induction, and antioxidant properties were evaluated by applying an MTT assay on a human hepatocyte cancer cell (HepG2), measuring Cas-3 gene expression, and conducting a DPPH antioxidant test, respectively. Compared to the non-entrapped Quercetin, Quercetin-entrapped nano-emulsions formed stable complexes with HSA and HTF by improving hydrophilic-hydrophobic interactions. The binding constant (BC), ΔH0, and ΔS0 indices for both the QuNE-HSA and QuNE-HTF complexes were measured at (4.92 × 105 and 11.99 × 104 M−1), (170.96 and −131.19 KJ.mol−1), and (−464.86 and 342.83J.mol−1K−1), respectively. QuNE lowered the HepG2 viability by up-regulating Cas-3 gene expression and thus inducing apoptosis. Moreover, a notable antioxidant impact on the QuNE was detected. Due to its ability in delivering Quercetin to HSA and HTF proteins and stabilizing their protein complexes, QuNE can be used as a suitable primary transporting agent whose formation of stable bio-accessible QuNE-HSA and –HTF protein complexes creates a safe and natural secondary delivery system, which has potential to be used as an efficient anticancer compound. Communicated by Ramaswamy H. Sarma

Thermodynamic study and preferential solvation of sulfamerazine in acetonitrile + methanol cosolvent mixtures at different temperatures

This paper discusses sulfamerazine (SMR) solubility in Acetonitrile (MeCN) + Methanol (MeOH) cosolvents at nine temperatures (278.15–318.15 K). Herein, the maximum SMR solubility was reached in a cosolvent mixture at the highest studied temperature, and the minimum SMR solubility was reached in neat methanol at the lowest studied temperature. Using experimental data, thermodynamic functions were calculated for both the solution and mixture using the Gibbs and van’t Hoff equations, thus determining that the solution process is endothermic with entropic favoring. In addition, the preferential solvation parameters (δx3,1), calculated using the inverse Kirkwood-Buff integrals (IKBI) method, are reported; SMR is preferentially solvated by MeOH in MeOH-rich mixtures, and in intermediate and MeCN-rich mixtures, the δx3,1 values indicate that SMR is not preferentially solvated by any of the two solvents in the mixture (MeCN + MeOH). Finally, eight models were assessed (Apelblat, van’t Hoff, Yaws, λh, Weibull, NRTL, Wilson, and Wilson modified), with all presenting mean relative deviation percentages (MRD%) under 6%, which indicates a good correlation with the experimental data.

Acetaminophen solubility in aqueous solutions of betaine-propylene glycol natural deep eutectic solvent at different temperatures

This work reports the aqueous solubility of acetaminophen (ACP), a most traditionally used analgesics and antipyretic drug, in betaine/propylene glycol deep eutectic solvent (Bet/PG DES) as a green solvent at temperatures ranging from 293.15 K to 313.15 K and atmospheric pressure (≈ 85 kPa). The ACP solubility in this solvent not only increases with increasing temperature, but also increases by increasing the DES portion reaching maximum values in the mixture of wDES = 0.90 at 313.15 K. The obtained experimental solubilities are accurately correlated with van’t Hoff, Jouyban-Acree, Jouyban-Acree-van’t Hoff, the modified Jouyban-Acree-van’t Hoff, the mixture response surface, the combined nearly ideal binary solvent/Redlich-Kister, the Buchowski-Ksiazczak and modified Wilson models. The accuracy of each model is evaluated by computing the average relative deviations (ARD%) and the results confirm that the the mixture response surface model (ARD% = 1.78) has a better correlation performance in comparison with the other models. Besides, thermodynamic behavior of ACP in the aqueous solution of Bet/PG DES is described with calculation of thermodynamic functions including Gibbs energy, enthalpy, and entropy of dissolution achieved from the van't Hoff and Gibbs equations. The results revealed that the ACP dissolution is an endothermic and entropy-driven process.

Complexation of Np(V) with the Dicarboxylates, Malonate, and Succinate: Complex Stoichiometry, Thermodynamic Data, and Structural Information

The complexation of Np(V) with malonate and succinate is studied by different spectroscopic techniques, namely, attenuated total reflection Fourier transform infrared (ATR FT-IR) and extended X-ray absorption fine-structure (EXAFS) spectroscopy, as well as by quantum chemistry to determine the speciation, thermodynamic data, and structural information of the formed complexes. For complex stoichiometries and the thermodynamic functions (log βn°(Θ), ΔrHn°, ΔrSn°), near infrared absorption spectroscopy (vis/NIR) is applied. The complexation reactions are investigated as a function of the total concentration of malonate ([Mal2-]total) and succinate ([Succ2-]total), ionic strength [Im = 0.5-4.0 mol kg-1 Na+(Cl-/ClO4-)], and temperature (Θ = 20-85 °C). Besides the solvated NpO2+ ion, the formation of two Np(V) species with the stoichiometry NpO2(L)n1-2n (n = 1, 2, L = Mal2-, Succ2-) is observed. With increasing temperature, the molar fractions of both complex species increase and the temperature-dependent conditional stability constants log βn'(Θ) at given ionic strengths are determined by the law of mass action. The log βn'(Θ) are extrapolated to IUPAC reference-state conditions (Im = 0) according to the specific ion interaction theory (SIT), revealing thermodynamic log βn°(Θ) values. For all formed complexes, [NpO2(Mal)-: log β1°(25 °C) = 3.36 ± 0.11, NpO2(Mal)23-: log β2°(25 °C) = 3.95 ± 0.19, NpO2(Succ)-: log β1°(25 °C) = 2.05 ± 0.45, NpO2(Succ)23-: log β2°(25 °C) = 0.75 ± 1.22], an increase of the stability constants with increasing temperature was observed. This confirmed an endothermic complexation reaction. The temperature dependence of the log βn°(T) values is described by the integrated Van't Hoff equation, and the standard reaction enthalpies and entropies for the complexation reactions are determined. Furthermore, the sum of the specific binary ion-ion interaction coefficients Δεn°(Θ) for the complexation reactions are obtained as a function of the t from the respective SIT modeling as a function of the temperature. In addition to the thermodynamic data, the structures of the complexes and the coordination modes of malonate and succinate are investigated using EXAFS spectroscopy, ATR-FT-IR spectroscopy, and quantum chemical calculations. The results show that in the case of malonate, six-membered chelate complexes are formed, whereas for succinate, seven-membered rings form. The latter ones are energetically unfavorable due to the limited space in the equatorial plane of the Np(V) ion (as NpO2+ cation).

Synthesis of a IAP antagonist analogue and its binding investigation with BSA/HSA

The development of new drugs especially novel anti-cancer drugs has become a hot-spot issue that catches scholars’ attention in every field. Here a IAP antagonist analogue (IAPA) was synthesized and characterized by NMR and HRMS spectra. Its interaction with proteins, including bovine serum albumin (BSA) and human serum albumin (HSA), were investigated by spectral methods and molecular simulation. Fluorescence quenching, together with UV absorption spectrum and time-resolved fluorescence spectrums indicated a static process in BSA/HSA-IAPA system. Thermodynamic parameters including ΔH and ΔS calculated by Vant't Hoff equation were all positive, showing that hydrophobic force was the major force in the interaction of compound IAPA and BSA/HSA. Site marker competitive displacement experiments proved that IAPA bound to site I at BSA/HSA. Synchronous fluorescence spectrum and three-dimensional fluorescence spectrum were also used to investigate the conformational changes of BSA/HSA after binding with compound IAPA. The above results were further verified by molecular docking.

Solubility determination and dissolution thermodynamic properties of dodecanedioic acid in binary-mixed solvents from T = (288.15–328.15) K

In this paper, the solubility and dissolution thermodynamic properties of dodecanedioic acid (DDDA) in four binary-mixed solvents (ethyl acetate + ethanol, ethyl acetate + acetic acid, and ethyl acetate + acetone) were investigated. The gravimetric method was employed to determine the mole fraction solubility of DDDA in different solvent ratios from 288.15 K to 328.15 K under the atmosphere. In the binary solvents of ethyl acetate + ethanol and ethyl acetate + acetic acid, when the composition was varied the solubility change was not monotonous, and the phenomenon of co-solvency occured. Furthermore, four models were employed to fit the solubility data, among which the modified Apelblat equation and CNIBS/R-K model had better fitting results. Finally, the dissolution thermodynamic properties of DDDA were analyzed based on the modified Van’t Hoff equation.

Combustion behavior and mechanism of Ti-25V-15Cr compared to Ti-6Al-4V alloy

A distinctive combustion phenomenon is revealed by promoted ignition combustion tests of Ti-25V-15Cr and Ti-6Al-4V alloys. The relationship between ignition temperatures and oxygen pressures obeys the Van't Hoff equation. The ignition temperatures of Ti-25V-15Cr are higher than that of Ti-6Al-4V due to the decomposition and volatilization of V2O5. However, the burning velocity of Ti-25V-15Cr is faster than that of Ti-6Al-4V, attributed to the different migration way of solid-liquid interface. The phase structure of the matrix is considered as the key factor that controls the spreading rate of the solid-liquid interface and the burning velocities of Ti-25V-15Cr and Ti-6Al-4V alloys.

Revealing the dissolution behavior of trans-p-methoxycinnamic acid in 12 organic solvents by parametric model and molecular simulation

trans-p-Methoxycinnamic acid (t-PMCA) is a cinnamic acid derivative with various pharmacological effects such as anti-colon cancer, antifungal, hepatoprotective, hypoglycemic, etc. In this paper, the solubilities of t-PMCA in 12 organic solvents were determined in the range of 283.15 K-323.15 K using gravimetric method. The solubility of t-PMCA increased with the increasing of temperature. Meanwhile, the experimental solubility data were verified and correlated using four thermodynamic models (Apelblat equation, λ h equation, Van’t Hoff equation and NRTL equation), and the relative standard deviations (ARD%) were all less than 7%. The simulated data agree well with those experimental data. In addition, the Hansen solubility parameter model and solvent properties were used to explain the dissolution behavior of t-PMCA in 12 organic solvents. The results showed that the dissolution behavior of t-PMCA was not determined by a single factor, but was the result of the comprehensive effect of various solubility parameters. In order to reveal the dissolution behavior of t-PMCA, the single-crystal structure of t-PMCA was analyzed, and molecular simulations (including Hirshfeld surface analysis, surface electrostatic potential, and radial distribution function) were performed, which showed that H⋯H and O⋯H contacts play a dominant role in the crystal arrangement and that there are hydrogen bonding interactions between t-PMCA and solvent molecules. Finally, the thermodynamic properties (ΔmixG, ΔmixH, and ΔmixS) of t-PMCA during the mixing process were calculated using the NRTL equation, and the results indicated that it is an entropy-driven spontaneous process.

Design, synthesis and protein-binding character of an acylhydrazone anticancer candidate

Acylhydrazone derivatives have potential antitumor activities due to their metabolic modulation effect in cancer cells. Herein, an acylhydrazone compound, p-nitrobenzaldehyde-p-methylbenzoylhydrazone (MNB), was designed, prepared and characterized. The interaction of MNB with carrier protein is systematically deciphered using spectroscopic, electrochemical and modeling techniques. Ultraviolet (UV) and electrochemical impedance spectroscopy (EIS) indicate that MNB can couple with albumin through hydrophobic interaction. Molecular probe experiments reveal MNB is located at Sudlow's site I in albumin. Stern-Volmer equation, Langmuir adsorption isotherm, van’t Hoff equation and Arrhenius equation are applied to analyze the thermodynamic and kinetic characteristics of the interaction. The results demonstrate that the interaction is a typical spontaneous process dominated by entropy, whose activationenergy is ca. 26.78 kJ·mol−1. Circular dichroism (CD) spectra show that MNB has a small impact on the conformation of albumin. Molecular docking investigation simulates the structural details of the new complex, which is consistent with experimental conclusions. This study provides comprehensive information on the interaction of MNB with carrier protein, which lays the basis for its application as a new anticancer candidate.

Heavy metals containment by vertical cutoff walls backfilled with novel reactive magnesium-activated slag-bentonite-sand: Membrane and diffusion behavior

This study aims to investigate the membrane and diffusion behavior of a novel vertical cutoff wall backfill comprised of reactive magnesium-activated slag, bentonite and sand (referred as MSBS backfill) for the containment of heavy metals in groundwater. The MSBS backfill specimens were subjected to a series of multi-stage chemico-osmotic tests using Pb(NO3)2 and Zn(NO3)2 solutions at different concentrations. Chemico-osmotic efficiency coefficient, effective diffusion coefficient, and retardation factor of the backfills were computed. For computing chemico-osmotic efficiency coefficient, the theoretical chemico-osmotic pressure differences were computed using both van't Hoff equation and water activity method. The results showed that the MSBS backfill exhibited semipermeable membrane behavior in tested solutions. The chemico-osmotic efficiency coefficients of the backfills decreased, whereas effective diffusion coefficients of heavy metal cations remained nearly constant, and retardation factors of heavy metal cations increased slightly with the increase of metal concentration. For the range of concentrations of Zn(NO3)2 in this study, the maximum percent error of theoretical chemico-osmotic pressure difference calculated using van't Hoff equation relative to that calculated using water activity method was 14.4%. A comparative assessment of reported chemico-osmotic efficiency coefficient, effective diffusion coefficient, and retardation factor values for various soil-bentonite backfills and geosynthetic clay liners with those for MSBS backfill was performed. Overall, the results are useful to assess containment performance of MSBS vertical cutoff walls at metal-contaminated groundwater sites.

Detection of interaction between ornidazole and albumin by using thermodynamic parameters

The binding of 1-chloro-3-(2-methyl-5-nitro-1H-imidazole-1-yl) propan-2-ol (Ornidazole) to human serum albumin (HSA) was studied by fluorescence and UV-visible spectroscopy. Interaction of ornidazole (OR) with HSA was identified by Stern-Volmer and Van’t Hoff equations. The binding constant, Kb and the thermodynamic parameters, ∆H, ∆S, and ∆G at different temperatures were calculated by several equations. Data shows that the fluorescence quenching mechanism of HSA with ornidazole may occur via static quenching. The thermodynamic parameters showed that van der Waals interactions and hydrogen bonds are the major forces for the interaction of ornidazole with HSA. The spectral changes of synchronous fluorescence suggested that both the microenvironment of OR and the conformation of HSA concerning their concentrations have changed during binding.  Â

Thermodynamic parameters of liquid–phase adsorption process calculated from different equilibrium constants related to adsorption isotherms: A comparison study

Adsorption thermodynamics is an integral part of the study of adsorption and plays a vital role in estimating adsorption mechanism (i.e., physisorption and chemisorption). For the liquid-phase adsorption, the equilibrium constant of some adsorption isotherm models (Langmuir, modified Langmuir, Langmuir–Freundlich, modified Langmuir–Freundlich, Liu, Khan, Sips, Hill, Toth, Redlich–Peterson, Koble–Corrigan, and Radke–Prausnitz models) and the constant of Henry and Freundlich models have been directly or indirectly applied for calculating the corresponding thermodynamic parameters (∆G°, ∆H°, and ∆S°). This study explored the effects of the selection of (1) the unit of adsorption isotherm (qevs. Ce), (2) the equilibrium constant of adsorption isotherm model, and (3) the linear and nonlinear forms of the van’t Hoff equation on the value (sign and magnitude) of the thermodynamic parameters. A commercial activated carbon was selected as a typical adsorbent to adsorb methylene green dye (target adsorbate) in solution. Results indicated that the constants of the Henry and Freundlich models could not be applied for calculating the thermodynamic parameters. The equilibrium constants of the modified Langmuir and modified Langmuir–Freundlich models were not suitable for calculating the thermodynamic parameters in this study compared to the other equilibrium constants of the Langmuir, Langmuir–Freundlich, Khan, Liu, Sips, Redlich–Peterson, Toth, Hill, Radke–Prausnitz, and Koble–Corrigan models. The thermodynamic parameters were calculated from thermodynamic equilibrium constant derived from the equilibrium constant of the Redlich–Peterson model or the Radke–Prausnitz model (the van’t Hoff equation: adj-R2 = 0.9999).