Positive Enthalpy Change Research Articles

Evaluation of calf thymus DNA binding of newly synthesize five 9 [sbnd]O[sbnd] Imidazolyl alkyl berberine derivative: A comparative multi-spectroscopic and calorimetric study

DNA binding with small molecule plays an important role in the designing of various anticancer drugs with greater efficacy. The five 9-O-imidazolyl alkyl berberine derivatives (BI) of different chain length has been synthesized and fully characterized. The binding study of calf thymus DNA with these newly synthesized berberine derivative was performed using various biophysical techniques. The binding affinity of BI to calf thymus DNA increased with increasing the chain length. The binding constant value obtained from UV–Vis spectral analysis was 1.84x105for BI1, 2.01x105for BI2, 1.51 × 106 for BI3, 3.66 × 106 for BI4, 6.68 × 106. Partial intercalative binding with strong stabilization of the DNA helix was revealed from circular dichroism spectral study and viscosity measurement. From the ITC experiment it was revealed that the bindings of BI1, BI2, BI3, BI4 and BI5 to calf thymus DNA were favoured by a large positive favourable entropy and negative enthalpy change and the highest spontaneity found for BI5. With the increase in chain length the binding was driven by a stronger entropy term with a higher binding constant indicates involvement of hydrophobic force for all these interaction. High binding affinities of calf thymus DNA with berberine-imidazole derivatives might be helpful for new drug design.

Thermally Activated Natural Clay for the Removal of Pharmaceutical Drug Levofloxacin

The adsorption behaviour of natural clay (NC) and thermal activated clay (TAC) mineral of the Panchanganga river flood zone sedimentfor levofloxacin (a class of fluoroquinolone antibacterial drug) has been studied. The isotherm and kinetic studies were performed using the batch technique. The results showed that TAC has 72.6% removal efficiency comparatively higher than NC, which is 62.8% at 120 min, pH = 7, dosage 0.40 g/L and Initial concentration of 18.69 mg/L. The kinetic and isotherm results indicate the adsorption of levofloxacin on NC and TAC follows Freundlich isotherm suggesting multilayer sorption and chemisorption as a rate-limiting step during the process. A plausible mechanism is proposed for the interaction of NC and TAC with levofloxacin from the results of the adsorption study. The negative free energy change and positive enthalpy change indicated that the adsorption process is spontaneous and endothermic.

Titania coated manganese ferrite nanocomposite for removal of copper and lead ions from wastewater: preparation, characterization and adsorption studies

ABSTRACT Herein, sol gel method was used to prepare titania coated manganese ferrite nanocomposite (TMFN) for wastewater treatment. The prepared TMFN nanocomposite was characterised using FTIR, SEM XRD, VSM, EDX, and BET techniques. The characterisation studies confirmed the formation of the nanocomposite and gave good information about its morphology. Batch adsorption method was applied to determine the optimal adsorption conditions towards Cu(II) and Pb(II) ions. The studied parameters were pH of the solution, contact time, adsorbent amount, initial concentration of ions and temperature. After finding out and applying the optimal adsorption conditions, maximum adsorption capacities of 550 and 460 mg/g were achieved for Cu(II) and Pb(II) ions, respectively. Isotherm and kinetic studies revealed that the current adsorption process is fitted well by Langmuir isotherm and pseudo-second order model. Thermodynamic investigations showed that the adsorption process is energetically favourable and takes place spontaneous with positive enthalpy change. Furthermore, the ability to regenerate and reuse the adsorbent confirmed its sustainability. The prepared nanocomposite could be reused many times with no significant loss in adsorption capacity.

Mass transfer process in the removal of Congo Red (CR) onto Natural Clay (NC): Kinetic, isotherm modeling, and thermodynamic study

Abstract Industrial growth and technological advancement have led to the worldwide introduction of pollutants of diverse nature into water bodies including pollutants such as dyes and organic contaminants. Their presence in industrial effluents or drinking water is a public health problem. The aim of this study was to evaluate the adsorption of Congo Red (CR) onto Natural Clay (NC) realized in a batch system. The effects of contact time, initial pH, stirring speed, temperature, adsorbent dose, and initial CR concentration on the adsorption capacity were investigated. The NC was characterized by the FTIR, DRX, BET, and point of zero charge. The experimental isotherm data follow well the Langmuir equation, providing a better fit of the equilibrium adsorption data. Under optimized conditions, up to 212.766 mg/g at 25 °C is removed from the solution. The adsorptions kinetics were found to follow rather a pseudo second-order kinetic model with a determination coefficient (R2) of 0.999. The adsorption isotherms at different temperatures have been used for the determination of thermodynamic parameters, i.e., the negative free energy ΔG0 (10.081 to 1.087 kJ/mol), positive enthalpy change ΔH0 Q5 (64 = 175 kJ/mol) values indicate that the overall CR adsorption is spontaneous and endothermic in nature.

Novel arylplatinum complexes with 2,2′‐dimethyl‐4,4′‐bithiazole: Synthesis, characterization, single crystal structure determination, and investigation of CT‐DNA interaction

Arylplatinum complexes containing 2,2′‐dimethyl‐4,4′‐bithiazole (a ligand with two different sulfur and nitrogen donor atoms, dm4bt) were synthesized by the reaction of [PtPh2(S (CH3)2)2] and [Pt(p‐CH3C6H4)2(S (CH3)2)2] with dm4bt in a 1:1 stoichiometry. In these heteroleptic platinum complexes, dm4bt was coordinated to the Pt centers as a chelating ligand using N2 donor atoms. The synthesized platinum(II) complexes were characterized by elemental analysis, conductometry, proton nuclear magnetic resonance (1H NMR), Fourier‐transform infrared spectroscopy (FTIR), and ultraviolet–visible (UV–Vis). The single crystal structure of the para‐tolyl platinum(II) complex, including dm4bt, was obtained by X‐ray crystallography. To investigate the interaction of DNA with the organoplatinum(II) complexes, different methods like fluorescence, absorption spectroscopy, and viscometry were employed. Furthermore, thermodynamic parameters such as entropy and enthalpy of the interaction between DNA and the complexes were calculated. According to the resulting positive entropy and enthalpy changes, it was demonstrated that the interaction originated from the hydrophobic forces.

Bio-coloration and ultraviolet protection finishing of tussah silk using chestnut leaf extract and its thermodynamic study

This study investigates the dyeing effects of chestnut leaf extract on tussah silk and aspires to create bio-colored and ultraviolet-resistant textiles. The results proved that post-mordanting with aluminum potassium sulfate and ferrous sulfate yielded better results than direct dyeing, the color strength value with ferrous sulfate mordant reached 10.9, and the color fastness of tussah silk with post-mordanting was rated above 4. Furthermore, the ultraviolet protection factor values reached 17, 39, 45, and 53 with control, direct dyeing, and post-mordanting with aluminum potassium sulfate and ferrous sulfate, respectively, revealing that the chestnut leaf extract could be a potential ultraviolet protection agent to increase the ultraviolet protection performance on tussah silk. In addition, the adsorption process and thermodynamic characteristics of chestnut leaf extract on tussah silk were examined. The results suggested that the Langmuir isotherm model adequately described the thermodynamic behavior of chestnut leaf extract on tussah silk. The positive enthalpy change indicated that the adsorption process was an endothermic process.

Palm Oil Shell Pyrolysis: Temperature Effect, Kinetics, and Thermodynamics Study

Palm oil shell (POS) is a solid waste from the oil palm industry and can cause environmental problems. This waste could convert into high-quality products such as biochar, bio-oil, and biogas that follow reaction mechanisms and kinetics parameters. This study aims to characterize palm oil shells and biochar, determine the optimum temperature of oil palm shell pyrolysis to produce biochar as briquettes and obtain kinetics and thermodynamic parameters. Palm oil shells were cleaned, sifted to a size of 0.4-2 mm, and dried at 105 ºC for 24 h. The pyrolysis was operated by 200 g of POS in a pyrolysis reactor and kept at 350 ºC, 375 ºC, and 400 ºC for 1 h. The bio-oil mass was recorded every 5 min, starting from the first drop after the temperature of pyrolysis reached. The optimum temperature for charcoal briquettes was 375 oC. The liquid and solid products were increased by increasing temperature, and gas products were decreased. The kinetics parameters of activation energy (E) and pre-exponential factor (A) were 20.7808 kJ mol-1 and 0.0821 min-1, respectively. Palm oil shell pyrolysis requires a lot of heat which is indicated by a positive enthalpy change (∆H) of 15.3934 kJ mole-1. The non-spontaneous reaction on pyrolysis was proved by a positive Gibbs free energy change (∆G) of 179.2998 kJ mole-1. Those parameters allow the process to be operated in optimal conditions, increasing the efficiency in future studies.

FAD-deficient P187S mutation of NAD(P)H:quinone oxidoreductase 1 (NQO1*2) binds and accelerates β-amyloid aggregation.

Alzheimer's disease (AD) is one of the most prominent neurodegenerative diseases. Results from animal and cellular models suggest that FAD-deficient forms of NAD(P)H quinone oxidoreductase 1 (NQO1) may accelerate the aggregation of Alzheimer's amyloid-β peptide (Aβ1-42). Here, we examined in vitro whether NQO1 and its FAD-deficient P187S mutation (NQO1*2) directly interact with Aβ1-42 and modify its rate of aggregation. When monitored using the fluorescence of either noncovalent thioflavin T (ThT) or HiLyte Fluor 647 (HF647) dye covalently attached to the Aβ1-42 peptide, the aggregation kinetics of Aβ1-42 were markedly more rapid in the presence of NQO1*2 than the wild-type (WT) NQO1. Experiments using apo-NQO1 indicate that this increase is linked to the inability of NQO1*2 to bind to FAD. Furthermore, dicoumarol, an NQO1 inhibitor that binds near the FAD-binding site and stabilizes NQO1*2, markedly decreased the aggregation kinetics of Aβ1-42. Imaging flow cytometry confirmed in-vitro coaggregation of NQO1 isoforms and Aβ1-42. Aβ1-42 alone forms rod-shaped fibril structures while in the presence of NQO1 isoforms, Aβ1-42 is incorporated in the middle of larger globular protein aggregates surrounded by NQO1 molecules. Isothermal titration calorimetry (ITC) analysis indicates that Aβ1-42 interacts with NQO1 isoforms with a specific stoichiometry through a hydrophobic interaction with positive enthalpy and entropy changes. These data define the kinetics, mechanism, and shape of coaggregates of Aβ1-42 and NQO1 isoforms and the potential relevance of FAD-deficient forms of NQO1 for amyloid aggregation diseases.

Adsorption performance and mechanism of cationic and anionic dyes by KOH activated biochar derived from medical waste pyrolysis

The massive generation of medical waste (MW) results in a series of environmental, social, and ecological problems. Pyrolysis is one such approach that has attracted more attention because of the production of value-added products with lesser environmental risk. In this study, the activated biochar (ABC600) was obtained from MW pyrolysis and activated with KOH. The adsorption mechanism of activated biochar on cationic (methylene blue) and anionic (reactive yellow) dyes were studied. The physicochemical characterization of biochar showed that increasing pyrolysis temperature and KOH activation resulted in increased surface area, a rough surface with a clear porous structure, and sufficient functional groups. MB and RYD-145 adsorption on ABC600 was more consistent with Langmuir isotherm (R2 ≥ 0.996) and pseudo-second-order kinetics (R2 ≥ 0.998), indicating chemisorption with monolayer characteristics. The Langmuir model fitting demonstrated that MB and RYD-145 had maximum uptake capacities of 922.2 and 343.4 mg⋅g−1. The thermodynamics study of both dyes showed a positive change in enthalpy (ΔH°) and entropy (ΔS°), revealing the endothermic adsorption behavior and randomness in dye molecule arrangement on activated-biochar/solution surface. The activated biochar has excellent adsorption potential for cationic and anionic dyes; hence, it can be considered an economical and efficient adsorbent.

Recovery of zinc from wastewater for zinc oxide synthesis via adsorption-desorption-chemical precipitation pathway

During the covid-19 pandemic large demand in gloves resulted in high consumption of zinc-oxide (ZnO) as an activator during the vulcanization process for glove production leading to the generation of zinc-containing wastewater requiring wastewater treatment to reduce zinc concentration below 2 mg/L. Zinc can be removed through adsorption, and this opens up an opportunity to recycle the removed zinc ions for ZnO synthesis. Therefore, the objective of this study is to evaluate the feasibility for ZnO synthesis via the adsorption-desorption-chemical precipitation pathway. Adsorption was conducted using palm shell activated carbon (PSAC), a low-cost adsorbent, and it exhibited a large surface area from BET analysis of 717 m2/g and showed excellent zinc adsorption possessing a Langmuir monolayer adsorption capacity of 3.6 mg/g. A Langmuir equilibrium (RL) of, 0 < RL < 1, was calculated for zinc adsorption showing favorable adsorption. PSAC exhibited endothermic adsorption attributed to the positive change in enthalpy of +ΔH = 63.356 kJ/mol. An initial adsorption characteristic of, Ri = 0.87 implies PSAC possesses fast initial adsorption properties, where most of the zinc removal happens within the first 30 min. HCl is an excellent desorption agent for zinc desorption achieving high average zinc desorption efficiency of 91.5 %. Chemical precipitation showed an average zinc conversion rate of 98 %. The resulting ZnO was characterized and it exhibited a high surface area of 97.4 m2/g after calcination (400 °C, 3 h), high purity and high crystallinity. The results confirmed the feasibility of zinc ion recovery for recycling to produce good quality ZnO.

Interaction of bisdemethoxycurcumin with cationic (cetyltrimethylammonium) + nonionic (Tween 20/Tween 60) mixed surfactants: Thermodynamic study and functional improvement

Bisdemethoxycurcumin (BDMC), one of the main curcuminoids, has numerous biological activities. However, the low solubility and stability of BDMC limit its application. In this work, in order to improve the solubility and stability of BDMC, we encapsulated BDMC using cetyltrimethylammonium bromide (CTAB) + Tween 20/Tween 60 mixed surfactants. The molar ratio of CTAB to Tween 20/Tween 60 was optimized by response surface analysis. The thermodynamic parameters (binding constant, enthalpy change, entropy change and Gibbs free energy change) for the interaction of BDMC with CTAB + Tween 20/Tween 60 mixed micelles were obtained by fluorescence spectroscopy and UV–visible absorption spectroscopy. Positive enthalpy change and entropy change indicated that hydrophobic interaction was the main driving force. Moreover, due to the longer alkyl chains of Tween 60, the encapsulation of BDMC by CTAB + Tween 60 mixed micelles was stronger. The encapsulation of BDMC in the hydrophobic alkyl chains by the mixed micelles was determined by fluorescence polarization technology, time-resolved fluorescence assay, and 1H nuclear magnetic resonance spectroscopy. Solubilization and stability experiments showed that the solubility of BDMC was improved and the alkaline hydrolysis of BDMC was inhibited due to the encapsulation of the mixed micelles. The improvement of the solubility and stability of BDMC was more obvious in CTAB + Tween 60 mixed micelles because of the stronger interaction between them. The above results indicated that CTAB + Tween 20/Tween 60 mixed micelles could be used to encapsulate BDMC to improve its solubility and stability.

Studying Kinetic and Thermodynamic Parameters of the Interaction of Ceftriaxone with Albumin Extracted from Healthy and Covid-19 Plasma

Because it has been well defined, bovine serum albumin (BSA) is highly suited to pharmacological effects, biotransformation, and bio-distribution of medicines initial research. Drug–protein interactions in the blood stream are known to have a significant impact on drug distribution, free concentration, and metabolism. Coronavirus disease 2019 (COVID-19) has spread globally as a severe pandemic. It is a serious threat to healthcare systems, economies, and is devastating to some populations, such as the elderly and those with comorbidities. Unfortunately, there is still no effective cure for COVID-19, especially the critically ill patients. The link between the mortality risk of patients hospitalized for COVID-19 and the function of blood albumin levels has been investigated. Because of albumin biological significance, the study goal conducted to apply spectroscopic methods to explore and comparing the kinetic and thermodynamic aspects of ceftriaxone's interaction with BSA, albumin isolated from healthy and covid-19 plasma. A pooled plasma from healthy and hospitalized covid-19 individuals (Karbala Province / Iraq) was used to purify albumin using HPLC technique. UV-vis spectrophotometric measurements of albumin‒ceftriaxone complex formation recorded at different pH ( 7, 7.2, 7.4, 7.6 &amp; 7.8) in phosphate buffer solution, and at six different temperatures (298, 301, 304, 307, 310 &amp; 313) K. The equilibrium constant and the thermodynamic parameter such as ΔG, ΔH and ΔS were calculated. The drug-albumin (BSA, healthy and Covid-19 albumin) complexes are stable in 60 to 300 minutes, as evidenced by the steady absorbance studies. The reaction is from the first false order for drug-albumin (BSA, healthy and covid-19 plasma) complexes. Our finding suggesting the reaction is from the first false order. In the case of plasma albumin from individuals infected with - Covid-19, the values of (R2) are closer together. This is because the medication dominates the formation of a more stable complex with albumin. The stoichiometric ratio (coordination number) of complex between ceftriaxone and albumin at 298 k and pH=7.4 is 1:1. The Gibbs free energy for albumin‒ ceftriaxone is negative, indicating that the reaction is spontaneous. The positive enthalpy of contact indicates that the process is endothermic, requiring energy input. Positive enthalpy and entropy change also refer to the hydrophobic association and electrostatic contact that occurs between albumin molecules and ceftriaxone. It is worth noting that the complex formed between bovine albumin and the medication has less absorbency at pH = 7.4. That is, the complex is more stable, and it prefers natural helical shapes. Additionally, as the pH value shifts away from physiological (&gt; 7.4 &lt;), the intensity of complex absorption increases. Keywords: Ceftriaxone, Bovine serum albumin, Covid-19 albumin, purification of albumin

Novel in-situ fabrication of L-methionine functionalized bionanocomposite for adsorption of Amido Black 10B dye

Due to abrupt increase in secondary pollution because of the non-biodegradable nature of adsorbents, it has become imperative to develop new green and sustainable adsorbents which further do not contribute any pollution. In order to fill this void here we have developed a novel green L-methionine functionalized kaolinite@cellulose (Meth-Kal@Cellulose) bionanocomposite for sequestration the dye Amido Black 10B from the aqueous solution. The maximum adsorption capacity (38.78 mgg−1) was observed at pH 2, dose 0.01 g and equilibrium was attained in 180 min. The adsorption capacity increased from 38.78 to 160.80 mgg−1 as the concentration increased from 20 to 100 mgL−1. The maximum monolayer adsorption capacity (172.14 mgg−1) was recorded at 30 °C. The experimental data was further validated with various kinetic models and pseudo second order (PSO) determine the best fit kinetic model with highest coefficient of (R2, 0.99). The positive change in enthalpy confirmed the endothermic nature of the adsorption process. The (Meth-Kal@Cellulose) bionanocomposite can be successfully recycled up to 4th cycle with a capacity of 56% in last cycle. To study the surface morphology and possible mechanism between the adsorbent and adsorbate, the (Meth-Kal@Cellulose) bionanocomposite was characterized by different analytical techniques like SEM, FTIR, TEM and XRD.

Oxidative desulfurization of a model fuel using MoO3 nanoparticles supported on carbon nanotubes catalyst: Examine most significance variables, optimization, kinetics and thermodynamics study

Molybdenum oxide nanoparticles MONP were dispersed on multiwall nanotubes MWNTs as an attempt to synthesize MONP/MWNTs catalyst, the synthesis method done by wet impregnation. The prepared catalyst was characterized by FTIR (Fourier –Transform Infrared Spectroscopy) and, XRD (X-ray diffraction), whilst the catalyst activity is done with catalytic oxidative desulfurization ODS reaction for oxidation dibenzothiophene DBT dissolved in heptane (model fuel) with hydrogen peroxide H2O2, in which catalyst activity investigation achieved via studying impact six from most affected variables on ODS reaction. The chosen variables are reaction temperature, contact time, sulfur initial sulfur concentration, stirring speed, oxidant/sulfur ratio and catalyst dosage, and then the studied variables were screened by application of Plackett-Burman design PBD to identify the more significant on response (DBT pollutant removal). DBT pollutant removal is referred to as sulfur removal efficiency. Analysis of variance ANOVA shows that the reaction temperature, oxidant/sulfur ratio, stirring speed, and sulfur initial concentration are the most significant from the chosen variables due to their F-values 37.60, 25.45, 11.62 and 6.71 respectively. Box –Behnken experimental design was used to complete the study the effect of the most significant more deeply on ODS reaction (sulfur removal efficiency),in which this part exhibited that sulfur removal efficiency at range between 51 and 93%, whilst the optimum sulfur removal efficiency was 96% at 70 °C,4.36, 957 rpm and 50 ppm for reaction temperature, oxidant/sulfur ration, stirring speed and initial sulfur concentration respectively. The study involves estimation of kinetics and thermodynamics parameters for ODS reaction; kinetics studying exhibited that ODS reaction followed pseudo-first-order reaction with activation energy (12.996 kJ/mol), while the thermodynamics study shows the low negative entropy change (-0.221 kJ /mol.K), positive enthalpy and free energy changes which confirm a high hydrate transition complex was formed.

Deciphering binding affinity, energetics, and base specificity of plant alkaloid Harmane with AT and GC hairpin duplex DNA.

Insights into binding efficacy and thermodynamic aspects of small molecules are important for rational drug designing and development. Here, the interaction of Harmane (Har), a very important bioactive indole alkaloid, with AT and GC hairpin duplex-DNAs has been reported using various biophysical tools. Detailed molecular mechanism with special emphasis on binding nature, base specificity, and thermodynamics have been elucidated via probing nucleic acids with varying base compositions. Har bound to both the DNA strands exhibited hypochromic effect in absorbance whereas bathochromic and hypochromic effects in fluorescence spectra. The binding constants estimated were in the order of 105 M-1 (higher for GC sequence compared with AT) with 1:1 stoichiometry. Noncooperative binding mode has been observed via intercalation in both the cases. The thermodynamic profile was obtained from temperature-dependent fluorescence experiments. Both Har-AT and Har-GC complexations were exothermic in nature associated with positive entropy and negative enthalpy changes. Salt-dependent studies revealed that the binding interaction was governed by nonpolyelectrolytic and hydrophobic interaction forces. The ligand-induced structural perturbation of the DNA structures was evident from the circular dichroism data. Molecular modelling data indicated towards the involvement of hydrophobic forces and hydrogen bonding.

DFT, MD simulations and experimental analysis of adsorptive complexation and isotope separation of gadolinium ion with macrocyclic crown ether embedded polymeric resin

Di-benzo-18-crown-6 ether (DB18C6) functionalized polymethyl acrylic acid (PMA) resin was synthesized after screening by employing density functional theory (DFT) and molecular dynamics (MD) simulations for the enrichment of gadolinium isotopes, Gd-155 and Gd-157. Batch adsorption and column chromatography studies were performed at various pH, gadolinium ion concentration and temperatures to check its efficacy and validation of theoretical approach. The adsorption capacity of gadolinium ion with the PMADB18C6 resin was found to be quite modest with a value of 1.128 mg/g. Both MD simulations and adsorption experiments confirm the Temkin type of adsorption isotherm. The positive entropy change along with the positive enthalpy change indicates that sorption of the Gd3+ ion with PMADB18C6 is entropy driven process. From the chromatography experiments, the lighter isotope (Gd-155) is seen to be depleted in the breakthrough volume samples which specify that the resin phase is depleted with heavier isotope (e.g Gd-160) contrast to natural Gd composition. The separation coefficient (ε) for Gd155/158, Gd156/158, Gd157/158, Gd155/160 and Gd157/160 isotopic pairs were found to be 1.67 × 10−3, 2.65 × 10−3, 5.40 × 10−4, 3.18 × 10−3 and 1.87 × 10−3 respectively. The experimental isotopic separation factor corroborates the DFT findings. Further, both DFT and MD simulations confirm the experimentally observed endothermic complexation of Gd3+ ion with PMADB18C6 resin. The present findings employing combined DFT, MD simulations and experimental approaches are expected to benefit in the fundamental understanding of molecular complexation based isotope separation and design and development of future gadolinium isotopic enrichment technologies using chemical exchange methods.

Microwave and ultrasound assisted extraction of phytocompounds from black jamun pulp: Kinetic and thermodynamics characteristics

The present study focuses on the extraction of phenolic compounds, anthocyanin and antioxidants from black jamun pulp by microwave and ultrasound assisted extraction process. The microwave-assisted extraction was carried out for 240 s at microwave power level of 100–400 W. The yield of total anthocyanin and total phenolic content in the microwave assisted extraction process at 400 W power level after an extraction period of 240 s was 8.197 mg of C3G g−1 and 37.671 40.632 mg GAE g−1, respectively. The ultrasound assisted extraction was performed at temperatures of 40, 50, 60, and 70 °C for 150 min. In the ultrasound assisted extraction at a sonication temperature of 70 °C, the yield of anthocyanin was 8.525 mg of C3G g−1, while the yield of the phenolic compound was 47.331 mg GAE g−1. The pseudo-second order model was found to be the most suitable model to represent the extraction kinetics of anthocyanin, phenolic compounds, and antioxidant activity of black jamun pulp. The effective diffusion coefficient for ultrasound assisted extraction of phenolic components, anthocyanin, and antioxidant activity in the temperature range of 40-70 °C was 5.704× 10−12–10.515 10−12, 2.485× 10−12 -8.507× 10−12, and 2.061× 10−12–11.977 × 10−12 m2.s−1 respectively. The negative Gibbs free energy change values for extraction of phenolic compounds and anthocyanin specified that the reaction was feasible and spontaneous. Thermodynamic parameters such as positive enthalpy change and positive entropy change indicated that the ultrasound assisted extraction process was endothermic and irreversible in nature.

Removal and recovery of phosphate using a novel calcium silicate hydrate composite starch cryogel

Phosphate is a major pollutant that deteriorates water quality and causes eutrophication, a novel calcium silicate hydrate composite cryogel (Cry-CSH) was thus successfully prepared for phosphate removal and recovery in this work. Calcium silicate hydrate (C–S–H) was mixed with the gel precursor (7.5% w/w) prepared from native starch and limewater (saturated calcium hydroxide solution as the cross-linker). The mixture was frozen and thawed for 3 cycles giving an interconnected macroporous composite. This had C–S–H nanoparticles (75 mg) immobilized on a monolithic floatable cryogel network (2.5 cm diameter × 1.0 cm height) enabling an easier recovery and without the losses that occur when using C–S–H nanoparticles. The phosphate adsorption reaches equilibrium at 120 min with adsorption capacity of 2.50 mgPO43−/gCry-CSH (65.42 mgPO43−/gC–S–H) under optimum conditions. Adsorption equilibrium data were well fit by the Freundlich isotherm model, while kinetic results were well fit by the pseudo second-order model. The calculated activation energy (Ea) of 43.9 kJ/mol indicates chemical adsorption, while a positive change in enthalpy (ΔH0, 19.3 kJ/mol) indicates the endothermic nature of phosphate adsorption. Cry-CSH can remove phosphate from wastewater and effluent samples with excellent removal efficiency (>98%). It can float on water surface for at least 105 days without damage, while its phosphate adsorbed form can be biodegraded within 10 days under soil buried conditions. Thus, this work demonstrated the significant potential of Cry-CSH for practical and environmentally friendly phosphate removal and recovery.

Effect of Saffron Flower Petal Extract as an Eco-Friendly Corrosion Bioinhibitor for Carbon Steel in 1 mol. L−1 HCl Solution

In this report, saffron flower petal extract (SFPE) as an inexpensive, natural, and green corrosion inhibitor for carbon steel in 1 mol. L−1 HCl solution is introduced. Gas chromatography coupled with a mass spectrometry detector (GC–MS) was used to identify the main compounds of saffron flower petal extract. Potentiodynamic polarization and electrochemical impedance spectroscopy as electrochemical techniques were investigated for the determination of corrosion resistance. Morphology and so elemental analysis of surface were analyzed by scanning electron microscopy equipped with energy-dispersive spectroscopy (SEM–EDS). The results showed that by increasing the concentration, the obtained inhibition efficiency is almost 81% and the alloy surface is less corroded. The effect of different temperatures of the solution (298–338 K) on the inhibitor efficiency was investigated that revealed increasing of temperature led to reduces inhibition efficiency, however, it is a suitable value at the highest temperature (74%). The values of positive enthalpy changes show that the corrosion process occurs as endothermic. Results of the Arrhenius plot showed that adsorption of SFPE on the alloy surface is defined as a physicochemical mechanism and so adsorption isotherm is best fitted with the Langmuir model.

Biomolecular interaction mechanism of an anticancer drug, pazopanib with human serum albumin: a multi-spectroscopic and computational approach

Pazopanib (PZP) is a multi-targeting tyrosine kinase inhibitor and is currently approved by FDA for the treatment of soft tissue sarcoma and renal cancer. Molecular interaction mechanism of PZP with human serum albumin (HSA) was explored under simulated physiological conditions (pH = 7.4), using fluorescence and UV absorption spectroscopy along with computational methods. Based on the inverse correlation between the Stern-Volmer constant (Ksv ) and temperature, it was concluded that PZP quenched the protein fluorescence through static quenching mechanism. This was also confirmed from the UV-vis absorption spectral results. Moderate binding affinity between PZP and HSA was evident from the Ka values (5.51 − 1.05 × 105 M−1) while PZP-HSA complex formation was driven by hydrophobic and van der Waals interactions as well as hydrogen bonds, as revealed by positive entropy change (ΔS = +98.37 J mol−1 K−1) and negative enthalpy change (ΔH = −60.31 kJ mol−1). Three-dimensional fluorescence spectral results disclosed microenvironmental perturbations around Trp and Tyr residues of the protein upon PZP binding. Interestingly, the addition of PZP to HSA significantly protected the protein against thermal stress. Competitive drug displacement results obtained with warfarin, phenylbutazone and diazepam elucidated Sudlow's Site I, positioned in subdomain IIA of HSA, as the preferred binding site of PZP which was well supported by molecular docking analysis, while molecular dynamics simulation results suggested the stability of the PZP-HSA complex. Communicated by Vsevolod Makeev