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Highlights • Isobaric VLE data for systems including diethanolamine, p-cresol, m-cresol were measured at 20.0 kPa. • The VLE data were well correlated by Wilson, NRTL and UNIQUAC models and chemistry theory's model. • The excess Gibbs free energy data for binary systems were calculated by the NRTL model. • The equilibrium constants for binary systems were obtained and the reaction thermodynamic parameters were predicted. Abstract Isobaric vapour–liquid equilibrium (VLE) data for two binary systems of p-Cresol (PC) + diethanolamine (DEA) and m-Cresol (MC) + DEA were measured at 20.0 kPa. The Herington area method was used to check the binary VLE data, and the results showed good thermodynamic consistency. Meanwhile, the Wilson, NRTL, UNIQUAC models and the chemistry theory proposed by Dolezalek were used to correlate the VLE data. The binary energy interaction parameters for activity models, and reaction equilibrium constants for chemistry theory were obtained. With help of the parameters obtained in this work, the NRTL model was used to predict the VLE data of the two binary systems at the pressure of 8.33 kPa. The predictive results were compared with the literature's data. At same time, the excess Gibbs free energy for the two binary systems, and infinite dilution activity coefficients for MC and PC in DEA were estimated. The calculated results showed that the DEA had slightly stronger interaction with PC than MC. [ABSTRACT FROM AUTHOR]

A series of silica gel supported amino-terminated PAMAM dendrimers (SG-G1.0 - SG-G3.0) were used for the removal of Cd(II) and Fe(III) from dimethylsulfoxide (DMSO). Various parameters that influence adsorption behaviors including temperature, contact time, and initial metal ion concentration were studied. The adsorption mechanism was revealed by combining the results of experiment and density functional theory (DFT) calculation. It indicates that the adsorption capacities for Cd(II) and Fe(III) are largest among the metal ions tested. The adsorption capacity of SG-G1.0 - SG-3.0 for Cd(II) and Fe(III) follows the order of SG-G2.0 > SG-3.0 > SG-G1.0. The adsorption isotherm shows the adsorption capacities for both metal ions increases with raising the temperature and initial metal ion concentration. The adsorption isotherm is consistent with Langmuir model and the adsorption process is dominated by chemical adsorption mechanism. Thermodynamic parameters indicates that the adsorption for both Cd(II) and Fe(III) is spontaneous and endothermic. Kinetic adsorption indicates that the adsorption equilibrium times for Cd(II) and Fe(III) is about 200 and 350 min, respectively, which can be described by a pseudo-second-order model and controlled by film diffusion process. FTIR analysis and theoretical calculation revealed that the carbonyl O atoms, secondary amine N atoms, and primary amine N atoms are the primary factor responsible for PAMAM adsorption by forming tetra- and penta-coordinated chelates with metal ions. [ABSTRACT FROM AUTHOR]

mRNA export from the nucleus depends on the ATPase activity of the DEAD-box protein Dbp5/DDX19. Although Dbp5 has measurable ATPase activity alone, several regulatory factors (e.g., RNA, nucleoporin proteins, and the endogenous small molecule InsP 6 ) modulate catalytic activity in vitro and in vivo to facilitate mRNA export. An analysis of the intrinsic and regulator-activated Dbp5 ATPase cycle is necessary to define how these factors control Dbp5 and mRNA export. Here, we report a kinetic and equilibrium analysis of the Saccharomyces cerevisiae Dbp5 ATPase cycle, including the influence of RNA on Dbp5 activity. These data show that ATP binds Dbp5 weakly in rapid equilibrium with a binding affinity ( K T ~ 4 mM) comparable to the K M for steady-state cycling, while ADP binds an order of magnitude more tightly ( K D ~ 0.4 mM). The overall intrinsic steady-state cycling rate constant ( k cat ) is limited by slow, near-irreversible ATP hydrolysis and even slower subsequent phosphate release. RNA increases k cat and rate-limiting P i release 20-fold, although P i release continues to limit steady-state cycling in the presence of RNA, in conjunction with RNA binding. Together, this work identifies RNA binding and P i release as important biochemical transitions within the Dbp5 ATPase cycle and provides a framework for investigating the means by which Dbp5 and mRNA export is modulated by regulatory factors. [ABSTRACT FROM AUTHOR]

Isothermal titration calorimetry (ITC) has given a mass of data on the binding of small molecules to proteins and other biopolymers, with particular interest in drug binding to proteins chosen as therapeutic indicators. Interpretation of the enthalpy data usually follows an unsound protocol that uses thermodynamic relations in circumstances where they do not apply. Errors of interpretation include incomplete definitions of ligand binding and equilibrium constants and neglect of the non-ideality of the solutions under study, leading to unreliable estimates of standard free energies and entropies of binding. The mass of reported thermodynamic functions for ligand binding to proteins estimated from ITC enthalpies alone is consequently of uncertain thermodynamic significance and utility. ITC and related experiments to test the protocol assumptions are indicated. A thermodynamic procedure avoiding equilibrium constants or other reaction models and not requiring protein activities is given. The discussion draws attention to the fundamental but neglected relation between the thermodynamic activity and bioactivity of drugs and to the generally unknown thermodynamic status of ligand solutions, which for drugs relates directly to effective therapeutic dosimetry. [ABSTRACT FROM AUTHOR]

Gas/particle (G/P) partitioning process is an important factor governing the transport and fate of chemicals in the atmosphere. Based on a large dataset of more than 700 pairs of air samples in gaseous and particulate phases with a wide ambient temperature range of 60 °C from −22 °C to +38 °C obtained from our Chinese POPs Soil and Air Monitoring Program, Phase 2 (China-SAMP-II), we investigated G/P partitioning behavior of polybrominated diphenyl ether (PBDEs) in Chinese air. We derived for the first time empirical equations to predict the values of slopes and intercepts for both subcooled-liquid–vapor-pressure (PL)-based and octanol-air-partition-coefficient (KOA)-based models as functions of temperature, and thus predicted partition quotient (KP) without assuming an equilibrium status and free of artifacts. These equations have been successfully applied to predict the values of KP for PBDEs in air of China and other countries in the north temperate zone (NTZ) and also at an Arctic site in East Greenland, and our results matched the monitoring data well at background, rural, urban, and suburban sites, but not at e-waste sites due to the unpredictable PBDE emissions at these sites. Our equations predicted that the ranges of slopes were 0.02–0.82 for log KP−log KOA plots and −0.82 to −0.02 for log KP−log PL plots at temperatures ranged of 60 °C from −22 °C to +38 °C. Our new KOA-based equation was compared with the Harner–Bidleman equation that was derived at a condition of equilibrium, and the results indicated that our new equation has a better performance than the Harner–Bidleman equation in describing G/P partitioning behavior of PBDEs in air as functions of log KOA. We also found for the first time that the G/P partitioning of PBDE congeners would become saturated in the particulate phase respect to the gas phase if the ambient temperature is low enough. A criterion to classify the equilibrium and nonequilibrium status for PBDEs was also established using log KOA. The study presented in this paper provides a useful tool for environmental scientists in both monitoring and modeling research on G/P partitioning behavior for PBDEs in air. [ABSTRACT FROM AUTHOR]

Highlights: [•] Regulators conclude formaldehyde & methylene glycol are chemically equivalent. [•] Chemical equivalence would also imply toxicological equivalence as well. [•] Experimental results show

To elucidate characteristic oxygen vacancy formation in layered perovskite (Sr, La) n+1Fe n O3n+1 with the perovskite layer number: n=3, oxygen vacancy content δ of the (Sr0.775La0.225)4Fe3O10−δ (SLF4310) was investigated using a titration technique and a thermogravimetric analysis. The equilibrium constant K for the reduction reaction: Oo×+2FeFe ∙ (Fe4+)=1/2O2+Vo ∙∙ +2FeFe ×(Fe3+) was estimated using the vacancy content δ. The Arrhenius plot of the K reveals slope change at approximately 775°C. From the Rietveld analysis, the oxygen vacancies are the most remarkable at the O2 (O4) sites at lower (higher) temperatures than about 800°C, which temperature is approximately comparable with that of slope change in the K. These facts mean that distribution of vacancy sites in the SLF4310 changes at approximately 775°C, accompanying no structural phase transition. The vacancy distribution change affects to the ion conductivity of the SLF4310. [ABSTRACT FROM AUTHOR]

Highlights: [•] Thermodynamic property of nano-ZnO reacted with acetic acid is related to its size. [•] Gibbs free energy, enthalpy, entropy and equilibrium constant depend on size of ZnO. [•] There is a linear relationship between them. [Copyright &y& Elsevier]

Abstract: It is widely recognized that the Graphic Industry handles toxic products and produces, in its various operations, toxic wastes. These wastes can cause serious environmental damages and can lead to severe health problems. In this work we report an efficient, simple and cheap to run method for the removal of some of the most common pollutants involved in the various stages of the Graphic Industry production, using a Solid-Phase Extraction (SPE) methodology. We have determined equilibrium constants, K eq, and adsorption (k up) and desorption (k off) rate constants for the extraction of benzene, xylene, toluene and ethylbenzene (BXTE) from water, using C18 disks. The removal of these compounds was monitored by UV–vis spectroscopy, at room temperature. Average extraction efficiencies were of 60% in a mixture of BXTEs and close to 80% when pollutants were assessed separately. Since the retention mechanism in the C18 disk is essentially governed by hydrophobic interactions between the compounds and the alkyl chains of the disk, we have also shown that these pollutants' lipophilicity plays an important role in the rationalization of their behavior during the extraction process. [Copyright &y& Elsevier]

Abstract: Steady-state reaction studies of acetic acid and ethanol were used to identify co-adsorbed acetic acid/ethanol dimers as surface intermediates within specific elementary steps involved in the esterification of acetic acid with ethanol on zeolites. A reaction mechanism involving two dominating surface species, an inactive ethanol dimeric species adsorbed on Brønsted sites inhibiting ester formation and a co-adsorbed complex of acetic acid and ethanol on the active site reacting to produce ethyl acetate, is shown to describe the reaction rate as a function of temperature (323–383K), acetic acid (0.5–6.0kPa), and ethanol (5.0–13.0kPa) partial pressure on proton-form BEA, FER, MFI, and MOR zeolites. Measured differences in rates as a function of zeolite structure and the rigorous interpretation of these differences in terms of esterification rate and equilibrium constants is presented to show that the intrinsic rate constant for the activation of the co-adsorbed complex increases in the order FER

Abstract: Cooperative binding of a ligand to multiple subsites on a protein is a common theme among enzymes and receptors. The analysis of cooperative binding data (either positive or negative) often relies on the assumption that free ligand concentration, L, can be approximated by the total ligand concentration, L T. When this approximation does not hold, such analyses result in inaccurate estimates of dissociation constants. Presented here are exact analytical expressions for equilibrium concentrations of all enzyme and ligand species (in terms of K d values and total concentrations of protein and ligand) for homotropic dimeric and trimeric protein–ligand systems. These equations circumvent the need to approximate L and are provided in Excel worksheets suitable for simulation and least-squares fitting. The equations and worksheets are expanded to treat cases where binding signals vary with distinct site occupancy. [Copyright &y& Elsevier]

Abstract: Thermodynamic properties and equilibrium constant of reaction in nanosystems were analyzed theoretically. The effects of sizes of nano-CuO on thermodynamic properties and equilibrium constant were studied using the reaction of nano-copper oxide and sodium bisulfate as a system. The experimental results indicate that with the sizes of reactant decreasing, the molar Gibbs free energy (Δr Gm ), the molar enthalpy (Δr Hm ) and the molar entropy (Δr Sm ) decrease, but the equilibrium constant (K) increases and there are linear trends between the reciprocal of sizes for nano-CuO and the values of Δr Gm , Δr Hm , Δr Sm and Ln K, which are in agreement with the theoretical analysis. [Copyright &y& Elsevier]