The activity of the intrinsically water-soluble enzyme ADAMTS13 correlates with the membrane state when bound to a phospholipid bilayer

Membrane-associated enzymes have been found to behave differently qualitatively and quantitatively in terms of activity. These findings were highly debated in the 1970s and many general correlations and reaction specific models have been proposed, reviewed, and discarded. However, new biological applications brought up the need for clarification and elucidation. To address literature shortcomings, we chose the intrinsically water-soluble enzyme a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) and large unilamellar vesicles with a relative broad phase transition. We here present activity measurements of ADAMTS13 in the freely dissolved state and the membrane associated state for phosphocholine lipids with different acyl-chain lengths (13:0, 14:0 and 15:0) and thus main phase transition temperatures. While the freely dissolved enzyme shows a simple Arrhenius behavior, the activity of membrane associated ADAMTS13 in addition shows a peak. This peak temperature correlates with the main phase transition temperature of the used lipids. These findings support an alternative theory of catalysis. This theory predicts a correlation of the membrane associated activity and the heat capacity, as both are susceptibilities of the same surface Gibb’s free energy, since the enzyme is attached to the membrane.

Investigation of The Influence of Halogens, Cycloalkanes, Carbonyls and the Hydroxyl Groups on The Reactivity of 1, 3-Butadienes With Imine Dienophile: Insight From DFT, MEDT, and QTAIM

The presence of nitrogen atom either on the diene or the dienophile structure gives rise to aza or imino-Diels-Alder reactions (DARs). Among hetero-DARs, imino-dienophiles yields numerous functionalized compounds with numerous biological activities including but not limited to antifungal, antibacterial and enzymatic properties. Density functional theory (DFT) using the B3LYP functional at the 6-31+G (d, p) basis set along with topological studies (QTAIM) were used for the investigation of 10 different (SD1-SD10) DARs which differ in the nature of substituents groups attached to the diene molecule. The study indicates higher electron density and stronger interaction for substituted dienes with the cycloalkanes, furan, carbonyl, and -OH groups. It was observed in the HOMO-LUMO energy differences that the bulky groups; SD3, SD4, and SD6 had destabilization energy of -7.86 and 0.09, -7.88 and 0.10 and -7.50 and -0.014 eV respectively in their HOMO and LUMO levels while the halogen substituted dienes SD1, SD2, and SD5 had -8.20 and -0.32, -8.31 and -0.34 and -8.19 and -0.20 eV respectively. The study showed that synthesis of hetero-nuclear aza-cyclohexene is achieved faster with furan substituent of energy gap 7.534 eV and molecular hardness of 3.677 compared to 7.799 (SD7) -8.100 eV (SD8) and 3.899 (SD7) - 4.050 (SD8) respectively scored by other substituents noting that smaller energy gap leads to higher reactivity. HCOCH3 (SD8) retarded the rate of the reaction by about 58% (unspontaneous) following the calculated Gibb’s free energy of activation while SD6 in the ELF analysis showed complete covalent character against other cycloalkanes that showed dual characteristics of a double and single bond between N-C at their transition states.

Thermodynamic and kinetic models for the removal of copper and cadmium using industrial effluents by mixed adsorbent

The potential of Activated Charcoal and bone Charcoal as a low cost material for the removal of copper and cadmium from synthetic metal solution was studied. A number of experiments were performed in order to determine the potential capacity of the adsorbent in terms of thermo Dynamic equilibrium from the batch data. The Positive values of change in Enthalpy show that the process is endothermic in nature for Cd (II) and the negative values of Change in Enthalpy shows that the process is exothermic in nature for Cu (II). The standard Gibb’s free energy values are positive which means that the process is not spontaneous in nature. The negative values of ΔS show that there is decrease in randomness at the solid/solution interface during the adsorption of copper. The study revealed that mixed adsorbent prepared by blending the activated charcoal and bone charcoal in 1: 1 ratio has more potential to act as an adsorbent for the removal of Cu and Cd from aqueous solution. The optimum temperature was found to be 40°C for both the metals. The higher correlation coefficient R2(0.9824) value shown that cadmium ions were well fitted the thermodynamic model comparing copper ions. The batch adsorption studies have been carried out for 2 hrs considering all the 6 parameters by optimizing each of them. The data obtained for optimized parameters were studied through fitting of kinetic models such as Pseudo-first order and Pseudo second order models for both Copper and Cadmium along with Correlation or regression coefficient (R2) values.

Kinetics And Thermodynamic Properties of Trametes Polyzona WRF03 Laccase

The effect of thermal treatment on the activity of laccase from Trametes polyzona WRF03 was studied at pH and temperature ranges of 3.0 to 6.5 and of 40 to 70 oC respectively. Kinetic data revealed that the heat inactivation of Trametes polyzona WRF03 laccase (TpL) was pH dependent and followed first-order kinetics. There was a positive correlation between activation energy (Ea) for thermal inactivation of TpL and the reaction pH. Highest activation energy, Ea, value of 175.49 kJ/mol was obtained at pH 6.0. On the contrary, the z-value decreased with a lowest value of 12.37 oC at pH 6.0. The high Ea value and low z-value were indicative of the thermo-stable nature of TpL which suggests that pH 6.0 had a compensatory stabilizing effect on TpL against its thermal denaturation. There was a gradual decrease in the enthalpy of denaturation (∆Ho) and Gibb’s free-energy with every 10 % rise in temperature within the investigated pH range, suggesting that TpL was more stable at 40 oC. Positive values of entropy of inactivation (ΔSº) at each temperature indicated that there was no aggregation during the inactivation processes. Thus, these results provided useful information about the behaviour of TpL under certain pH and temperature combination with respect to biotechnological application. Thus, the kinetic and thermodynamic data could be used to design a model to predict the thermal inactivation of TpL during industrial application.

Central Composite Design Based Adsorption Study of Malachite Green Dye Using Reduced Graphene Oxide Nano-Adsorbent

The adsorption of Malachite Green (MG) dye was well studied and elucidated from the liquid phase using reduced Graphene Oxide (rGO) nano-adsorbent. The desired levels of the factors were determined to be the amount of adsorbent of 0.2 g/L, pH of 8.5, the concentration of the dye as 100 mg/L and the sonication time of 50 min by Central Composite Design (CCD). The removal of the dye was found to be 95% at the optimum levels of the variables. Furthermore, the removal of the dye was higher at the higher values of the amount of adsorbent and pH. Langmuir and Temkin models were observed significant for rGO-MG dye system. The values of Gibb's free energy, the entropy and the enthalpy were found to be -10.502 KJ/mol, 34.314 KJ/mol and 0.147 KJ/mol.K, respectively. The kinetic data were also found well fitted to pseudo second order kinetics model for the said system. Afterwards, the cost of the process was found to be US$0.654/dm3. Therefore, the adsorption process effectively removed the dye from the simulated aqueous phase using rGO nano-adsorbent.

Thermo Acoustic Parameters of Tetrabutylammonium Borate and Perchlorate in Non-Aqueous Solvents

Interactions of electrolytes in a binary mixture can be determined by various techniques. Ultrasonic velocity measurements prove to be one of the important tools for measuring various acoustic properties at variable temperature. Thermo acoustic parameters like Isentropic compressibility (κs),Acoustic impedance (Z), Free volume (Vf), Absorption coefficient (Abscoeff), Intermolecular free length (Lf), Gibb’s free energy (ΔG), Relaxation time (τ), Rao’s constant (Rm), Internal pressure (πi), Wada’s constant (w), and Entropy (H) for Tetrabutylammonium tetraphenylborate (Bu4NBPh4) and Tetrabuty lammonium perchlorate (Bu4NClO4) was calculated using experimental ultrasonic velocities, viscosities and densities at three different temperatures (298K, 308 K and 318K) and 1 atmospheric pressure in non-aqueous solvents like Dimethylsulfoxide (DMSO), Pyridine (Py) and their binary mixtures at 0, 20, 40, 60, 80 and 100 mol% of Py at variable temperatures ranging from 298K to 318K. Both Bu4NBPh4, Bu4NClO4, showed an increase in the ultrasonic velocity values at all the temperatures. This shows that molecular interactions are taking place in both the electrolytes. These increases in the molecular interactions with increase in the concentration of electrolytes in the solvent mixture were discussed in terms of solvent structural effects. And results showed the greater molecular interaction in DMSO rich regions.

Thermodynamic and Adsorption Study of the Corrosion Inhibition of Mild Steel by Aframomum chrysanthum Extract in 0.1 M Hydrochloric Acid Solution

The study reports the corrosion inhibition activity of methanol extract of Aframomum chrysanthum on mild steel in 0.1 M HCl, using gravimetry analysis. The weight loss of the mild steels was observed to increase with increasing immersion time. The inhibition efficiency (%IE) was also observed to have increased with increasing concentrations of the inhibitor but decreases with increasing immersion time. The effect of temperature change on the inhibition efficiency was also studied and it was observed that for every increase in temperature there was a corresponding increase in weight loss and decreased in the %IE. The highest values of %IE; 46.66, 56.66, 60.0, 80.0 & 93.33 was observed at temperature 303 K for 0.2, 0.4, 0.6, 0.8 & 1.0 g/L respectively. Activation energy (Ea) values and the enthalpy values reviews that the adsorption process followed a physisorption’s mechanism. Change in enthalpy (ΔH) and entropy change (ΔS) of the reaction was positive indicating the endothermic nature and the spontaneity of the reaction. Three adsorption isotherms were tried on the inhibition process and only the Temkin isotherm gave the best fit with R2 value of 0.903, describing the best adsorption mechanism. The adsorption equilibrium constants K­ads were positive, indicating the feasibility of the adsorption of the inhibitor to the metal surface. Gibb’s Free Energy change of adsorption, ΔGads are negative indicating that the adsorption of the extract of Aframomum chrysanthum on mild steel surface is spontaneous. The values of ΔGads shows physisorption mechanism. All confirming that Aframomumm chrysanthum extract is a good corrosion inhibitor on mild steel in 0.1 M HCl.

Direct Yellow 8 Azo Removal by Bentonite Clay Solution: Experimental and Theoretical Studies

In the theoretical part, removal of direct yellow 8 (DY8) from water solution was accomplished using Bentonite Clay as an adsorbent. Under batch adsorption, the adsorption was observed as a function of contact time, adsorbent dosage, pH, and temperature. The equilibrium data were fitted with the Langmuir and Freundlich adsorption models, and the linear regression coefficient R2 was used to determine the best fitting isotherm model. thermodynamic parameters of the ongoing adsorption mechanism, such as Gibb's free energy, enthalpy, and entropy, have also been measured. The batch method was also used for the kinetic calculations, and the day's adsorption assumes first-order rate kinetics. The kinetic studies also show that the intraparticle diffusion process was active. Density Functional Theory (DFT) was used to study the dye structure with Gaussian 09 and predict the active site in a molecule using total electron density (TED) and electrostatic surface potential (ESP).

Van der Waals black hole as a heat engine

In this work, we attempt to study the thermodynamic behavior of static Van der Waals (VdW) black hole with an anti-de Sitter (AdS) background in the extended phase space. Treating the negative cosmological constant as thermodynamic pressure, we obtain the expressions for enthalpy, Gibb’s free energy and Helmholtz free energy. We study the stability and Joule–Thomson expansion for the black hole. Next, we construct a heat engine by considering the VdW black hole as the working substance. We investigate the maximum efficiency of the black hole heat engine for the Carnot cycle. We also discuss the work done and the efficiency of a new heat engine. Finally, we study the efficiency of the black hole heat engine for the Rankine cycle.

Spectroscopic detection of Hg2+ in water samples using fluorescent carbon quantum dots as sensing probe

Mercury (Hg2+) is remarked as toxic and hazardous element to global environment. Here, carbon quantum dots (CQDs) were synthesized by simple microwave assisted technique for Hg2+ detection in water samples via. fluorescence quenching and FT-IR spectroscopic approach. The morphology and chemical structure of synthesized CQDs was investigated by TEM, FT-IR, 13C-NMR, fluorescence and UV-vis spectroscopic technique. The resultant CQDs bears spherical morphology with an average size of 2–4 nm. The binding parameters, as Stern-Volmer quenching constant (Ksv) and binding constant for CQDs-Hg system was investigated by fluorescence method, whereas UV-vis techniques was employed for determination of thermodynamic parameters, as Gibb’s free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) at three different temperature (295, 298 and 305 K). Moreover, selectivity assay for Hg2+ detection has been studied in presence of other metal ions by FT-IR as well as fluorescence spectroscopy. Analytical assay was also successfully applied for Hg2+ in spiked water samples collected from different areas of Chhattisgarh, with 98–99 recovery %. The detection of Hg2+ has been demonstrated in the range of 0 to 5.0μM with 3.25 nM detection limit. The present method is found to be simple, highly sensitive and selective for sensing of Hg2+ in aquatic environmental samples using CQDs as sensing probe.