Negative Enthalpy Change Research Articles

Entropically driven binding of Camptothecin in the minor groove of salmon testes DNA

The present study focuses on binding association of Camptothecin (CMT) towards natural deoxy-ribonucleic acid (salmon testes, ST) under physiological conditions of pH 7.4. Extensive spectroscopic and computational techniques have been employed to elucidate thermodynamics of the said interaction. UV and fluorescence analyses portrays significant intensity changes (hyper-chromic and hypsochromic) in the spectra, which confirms effective CMT binding to ST DNA. The McGhee-von Hipple method and Scatchard plot analyses estimated the binding affinities in 105 M−1 range. Associated thermodynamic data revealed spontaneous and exothermic nature of binding. Temperature-dependent fluorescence showed negative change in enthalpy and positive change in entropy, leading to the formation of a 1:1 adduct. Non-polyelectrolytic forces appeared to be the driving force of the ligand-DNA interaction, according to salt-dependent fluorescence. Dye displacement assay, viscosity study, DNA melting, iodide quenching, urea denaturation assay examined the minor groove nature of CMT. In silico docking study examined precise molecular representations of the minor groove binding mechanism that formed between the complex, and the study's findings were consistent with the experimental results. Simulation studies also validated the experimental analysis and docking data. These findings could expedite the process of creating new and improved CMT molecular derivatives and help in the creation of DNA-targeted medicines, which may be beneficial from a pharmaceutical point of view.

Core-shell V2O5- Gum ghatti grafted poly (acrylamide-co-methacrylic acid) adsorbent for the removal of methylene blue dye in water: Kinetic, equilibrium and thermodynamic studies

Herein, vanadium pentoxide (V2O5) encapsulated Gum ghatti grafted poly(acrylamide-co- methacrylic acid) adsorbent was synthesized to remove methylene blue dye from water. The materials were characterized by FTIR, TEM, SEM, Raman and XRD analysis. Batch adsorption studies were performed on the materials. Several variables' effects on methylene blue removal, including pH, contact time, initial dye concentration, and adsorbent dosage, were examined. Kinetics and thermodynamic analysis were also carried out for the adsorbent-adsorbate interaction to determine the maximum adsorption and mechanism for adsorption. By using UV-Vis spectrophotometric analysis, the dye concentration was evaluated both before and after adsorption. Langmuir, Freundlich, and Dubini-Radushkevic's isotherm models were used to analyze the adsorption data. Results showed a maximum adsorption efficiency of 92 % at a pH of 9 and 0.2 g as the maximum adsorbent dosage. The study followed the Langmuir isotherm model with a correlation coefficient (R2) of 0.9995. The results from the kinetic studies show a pseudo-second-order mechanism. The negative values of the Gibbs free energy change ΔG° ranging from −10.57 KJmol−1 to −9.64 Kmol−1 within the temperatures of 298 K to 313 K is an indication of a spontaneous process. A negative enthalpy change (ΔH° = −29.05 KJmol−1) shows an exothermic process and a negative entropy change (ΔS° = −0.06 KJmol−1) represents a highly ordered system. ANOVA in Microsoft Excel and other statistical analyses were used to evaluate the effects of time, pH, concentration, dose, temperature, and other factors on the effectiveness of dye adsorption. Importantly, every parameter that was investigated showed statistically significant impacts on the removal of dye (p < 0.05), revealing their important impact on the adsorption process.

Molecular interaction of a protease inhibitor, leupeptin, with human serum albumin: Insights from calorimetry, spectroscopy, microscopy, and computational approaches

Leupeptin (LPN) possesses anti-inflammatory and inhibitory effects on periodontitis and gingivitis, and it also inhibits human coronavirus and SARS-CoV-2 in cells. The characterisation of its interaction with human serum albumin (HSA), the key transport protein in the blood circulation of the human body, contributes essential information to the drug's pharmacokinetic properties. Various techniques, such as isothermal titration calorimetry (ITC), circular dichroism (CD) spectroscopy, atomic force microscopy (AFM), molecular docking, and molecular dynamics simulation (MDS), were employed to characterise the LPN-HSA interaction. The ITC result revealed a moderate binding affinity in the LPN-HSA interaction with a binding constant (Ka) value of 4.27 ± 0.27 × 106 M−1. The thermodynamic analysis indicated that LPN binding to HSA was spontaneous, resulting from a negative Gibbs free energy change (∆G° = − 37.91 ± 0.04 kJ mol−1) and involving an exothermic reaction due to a combination of a negative enthalpy change (∆H° = − 11.4 ± 0.9 kJ mol−1) and a positive entropy change (∆S° = 88.82 ± 3.4 J mol−1K−1). The HSA secondary structure remained unaltered upon the addition of LPN, as evident from the far-UV CD results. AFM results showed HSA morphological changes induced by LPN binding due to the occurrence of aggregates in the LPN-HSA complex. Molecular docking results predicted that LPN preferably binds to site III of HSA, involving hydrogen bonds, electrostatic, van der Waals forces, and hydrophobic forces. The MDS demonstrated a slight deviation and fluctuation, which supported the overall stability of the LPN-HSA system. Thus, these findings provide additional information on the pharmacokinetics of this drug and contribute to designing new drugs for clinical use, particularly those related to inflammatory diseases.

A sustainable and economical solution for CO2 capture with biobased carbon materials derived from palm kernel shells.

This study investigates the synthesize of activated carbon for carbon dioxide adsorption using palm kernel shell (PKS), a by-product of oil palm industry. The adsorbent synthesis involved a simple two-step carbonization method. Firstly, PKS was activated with potassium oxide (KOH), followed by functionalization with magnesium oxide (MgO). Surface analysis revealed that KOH activated PKS has resulted in a high specific surface area of 1086 m2/g compared to untreated PKS (435 m2/g). However, impregnation of MgO resulted in the reduction of surface area due to blockage of pores by MgO. Thermogravimetric analysis (TGA) demonstrated that PKS-based adsorbents exhibited minimal weight loss of less than 30% up to 500 °C, indicating their suitability for high-temperature applications. CO2 adsorption experiments revealed that PKS-AC-MgO has achieved a higher adsorption capacity of 155.35 mg/g compared to PKS-AC (149.63 mg/g) at 25 °C and 5 bars. The adsorption behaviour of PKS-AC-MgO was well fitted by both the Sips and Langmuir isotherms, suggesting a combination of both heterogeneous and homogeneous adsorption and indicating a chemical reaction between MgO and CO2. Thermodynamic analysis indicated a spontaneous and thermodynamically favourable process for CO2 capture by PKS-AC-MgO, with negative change in enthalpy (- 0.21 kJ/mol), positive change in entropy (2.44 kJ/mol), and negative change in Gibbs free energy (- 729.61 J/mol, - 790.79 J/mol, and - 851.98 J/mol) across tested temperature. Economic assessment revealed that the cost of PKS-AC-MgO is 21% lower than the current market price of commercial activated carbon, indicating its potential for industrial application. Environmental assessment shows a significant reduction in greenhouse gas emissions (381.9 tCO2) through the utilization of PKS-AC-MgO, underscoring its environmental benefits. In summary, the use of activated carbon produced from PKS and functionalised with MgO shows great potential for absorbing CO2. This aligns with the ideas of a circular economy and sustainable development.

Exploring the molecular binding mechanism of 6-fluoro, 4-hydroxy, 2- methyl quinoline with TiO2 nanoparticles: A spectroscopic, thermodynamic, and insights into the solvatochromic effect.

This study investigates the interaction between titanium oxide nanoparticles (TiO2 NPs) and the heterocyclic fluorophore 6-fluoro,4-hydroxy,2-methylquinoline (6-FHMQ), aiming to understand fluorescence quenching mechanisms and thermodynamic characteristics. Spectroscopic techniques including spectrofluorometry (FL) and spectrophotometry (UV-Vis) were used, with a lifetime decay (τ) of 0.18ns for 6-FHMQ measured using time correlated single photon counting (TCSPC). The interaction between 6-FHMQ and TiO2 NPs revealed a mix of static and dynamic fluorescence quenching mechanisms, with increasing quenching constants (Ksv) and a higher bimolecular quenching rate constant (Kq). The dynamic nature was highlighted by a temperature-dependent increase in binding sites from 1 to ~ 2. Spontaneous complexation was affirmed by negative change in free energy (ΔG), with negative change in enthalpy (ΔH) and a positive change in entropy (ΔS) values indicating favorable electrostatic and ionic interactions. The impact of varying TiO2 NP concentrations on 6-FHMQ absorption was analyzed using the Benesi-Hildbrand equation, with a quantum yield of 0.61 determined. By forster resonance energy transfer (FRET) theory, the proximity between 6-FHMQ and TiO2 NPs was found to be less than 70Å. Ground and excited state dipole moments of 6-FHMQ in different solvents were calculated to demonstrate solvent sensing ability and charge transfer properties. Ultimately, this study serves as a testament to the power of scientific innovation in the realms of drug delivery and tissue engineering.

Evaluating the biomolecular interaction between delamanid/formulations and human serum albumin by fluorescence, CD spectroscopy and SPR: Effects on protein conformation, kinetic and thermodynamic parameters

Delamanid is an anti-tuberculosis drug used for the treatment of drug-resistant tuberculosis. Since delamanid has a high protein bound potential, even patients with low albumin levels should experience high and rapid delamanid clearance. However, the interaction between delamanid and albumin should be better controlled to optimize drug efficacy. This study was designed to evaluate the binding characteristics of delamanid to human serum albumin (HSA) using various methods: fluorescence spectroscopy, circular dichroism (CD), surface plasmon resonance (SPR), and molecular docking simulation. The fluorescence emission band without any shift indicated the interaction was not affected by the polarity of the fluorophore microenvironment. The reduction of fluorescence intensity at 344 nm was proportional to the increment of delamanid concentration as a fluorescence quencher. UV-absorbance measurement at the maximum wavelength (λmax, 280 nm) was evaluated using inner filter effect correction. The HSA conformation change was explained by the intermolecular energy transfer between delamanid and HSA during complex formation. The study, which was conducted at temperatures of 298 K, 303 K, and 310 K, revealed a static quenching mechanism that correlated with a decreased of bimolecular quenching rate constant (kq) and binding constant (Ka) at increased temperatures. The Ka was 1.75–3.16 × 104 M−1 with a specific binding site with stoichiometry 1:1. The negative enthalpy change, negative entropy change, and negative Gibbs free energy change demonstrated an exothermic-spontaneous reaction while van der Waals forces and hydrogen bonds played a vital role in the binding. The molecular displacement approach and molecular docking confirmed that the binding occurred mainly in subdomain IIA, which is a hydrophobic pocket of HSA, with a theoretical binding free energy of −9.33 kcal/mol. SPR exhibited a real time negative sensorgram that resulted from deviation of the reflex angle due to ligand delamanid-HSA complex forming. The binding occurred spontaneously after delamanid was presented to the HSA surface. The SPR mathematical fitting model revealed that the association rate constant (kon) was 2.62 × 108 s−1M−1 and the dissociation rate constant (koff) was 5.65 × 10−3 s−1. The complexes were performed with an association constant (KA) of 4.64 × 1010 M−1 and the dissociation constant (KD) of 2.15 × 10−11 M. The binding constant indicated high binding affinity and high stability of the complex in an equilibrium. Modified CD spectra revealed that conformation of the HSA structure was altered by the presence of delamanid during preparation of the proliposomes that led to the reduction of secondary structure stabilization. This was indicated by the percentage decrease of α-helix. These findings are beneficial to understanding delamanid-HSA binding characteristics as well as the drug administration regimen.

Function of Si on the microstructure, mechanical property and high temperature corrosion resistance of TiAlMoNbWSix HEA film

TiAlMoNbWSix (x = 0, 0.3, 0.5, 0.7) HEA films were deposited by magnetron co-sputtering technology to enhance the wear and high-temperature corrosion resistance of the copper. The structure of films was regulated by changing the content of Si to improve the comprehensive properties. The lattice distortion and negative mixing enthalpy change caused by the introduction of Si transformed the film from BCC structure to amorphous. With the increase of Si content, the wear resistance and the oxidation resistance were effectively improved. The characteristic delayed diffusion effect of HEA film allowed all the TiAlMoNbWSix films to successfully block the diffusion between Zn and Cu.

Photophysical Properties of Sinapic Acid and Ferulic Acid and Their Binding Mechanism with Caffeine.

Sinapic acid (SA) and ferulic acid (FA) are bioactive compounds used in the food, pharmaceutical, and cosmetic industries due to their antioxidant properties. In this work, we studied the photophysical properties of SA and FA in different solvents and concentrations and their interactions with caffeine (CF), using ultraviolet-visible (UV-Vis), fluorescence spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The findings show that the quantum yield, fluorescence lifetime, radiative decay rates, and non-radiative decay rates of SA and FA are influenced by the concentrations and solvent polarity. The interaction between SA and FA with CF was also studied using UV-Vis and fluorescence spectroscopy. The results indicate that the CF quenched the fluorescence intensity of SA and FA by static quenching due to the formation of a non-fluorescent complex. The van't Hoff equation suggests that the van der Waals forces and hydrogen bonds force were responsible for the interaction between SA and CF, as indicated by a negative change in enthalpy ( < 0) and a negative change in entropy ( < 0). On the other hand, the interaction between FA and CF was primarily controlled by electrostatic force, as indicated by a negative change in enthalpy ( < 0) and a positive change in entropy ( > 0). The negative change in Gibbs free energy ( ) indicates that both compounds underwent a spontaneous binding process.

COMPLEXATION OF SILVER (I) C 2-ETHYLIMIDAZOLE

The acid-base properties of 2-ethylimidazole were studied by pH-metric titration (EM). Using the literature data and our own results, a number of changes in the acid-base properties (pКa) of imidazoles have been established: ethylimidazole (7,93)&gt; imidazole (7.05)&gt;2-phenylimidazole (6,48)&gt;2-aminobenzimidazole (6,11)&gt; benzimidazole (5,53)&gt;2-phenylbenzimidazole (5,23)&gt;2-mercaptoimidazole (2,97)&gt;1-methyl-2-mercaptoimidazole (2,11). Method The process of complexation of silver(I) with 2-ethylimidazole in the temperature range of 273-318K was investigated using potentiometric titration using a silver electrode. It has been established that the increase in temperature does not affect the stoichiometric composition of complex particles formed in the Ag-EM-H2O system. The results obtained show that as the temperature increases, the stability constants decrease. On the basis of diagrams, the distribution of complex particles depending on the ligand concentration is shown that in System Ag-EM-H2O is mainly dominated by the bis-substituted complex, the yield of which at EM concentrations above 1·10-2 mol/l is 100%. The thermodynamic functions of the formation of 2-ethylimidazole silver complexes have been calculated. It has been established that complexation reactions are exothermic. Spontaneous occurrence of complexation reactions in the system Ag-EM-H2O contributes to a negative change in enthalpy.

Elimination of Pharmaceutical Compounds from Aqueous Solution through Novel Functionalized Pitch-Based Porous Adsorbents: Kinetic, Isotherm, Thermodynamic Studies and Mechanism Analysis.

The long-term presence of PPCPs in the aqueous environment poses a potentially significant threat to human life and physical health and the safety of the water environment. In our previous work, we investigated low-cost pitch-based HCP adsorbents with an excellent adsorption capacity and magnetic responsiveness through a simple one-step Friedel-Crafts reaction. In this work, we further investigated the adsorption behavior of the prepared pitch-based adsorbents onto three PPCP molecules (DFS, AMP, and antipyrine) in detail. The maximum adsorption capacity of P-MPHCP for DFS was 444.93 mg g-1. The adsorption equilibrium and kinetic processes were well described through the Langmuir model and the proposed secondary kinetic model. The negative changes in Gibbs free energy and enthalpy reflected that the adsorption of HCPs onto PPCPs was a spontaneous exothermic process. The recoverability results showed that the adsorption of MPHCP and P-MPHCP onto DFS remained above 95% after 10 adsorption-desorption cycles. The present work further demonstrates that these pitch-based adsorbents can be used for multiple applications, which have a very extensive practical application prospect.

Molecular recognition of synthetic RNAs by phenothiazinium dyes methylene blue and new methylene blue: Thermodynamic approach

Many biological process and function centers around recognition of double stranded RNA as it impacts numerous pathways associated with maturation of cellular RNA. This work assembles an intricate thermodynamic profiling of the phenothaizinium dyes methylene blue and new methylene blue with three double stranded ribonucleic acids, poly(A).poly(U), poly(C).poly(G) and poly(I).poly(C) with aid of thermal helix melting, isothermal titration calorimetry and differential scanning calorimetry experiments. Isothermal titration calorimetry had put forward that highest binding affinity was observed for poly(A).poly(U)-dye binding while the order varied as poly(A).poly(U) > poly(C).poly(G) > poly(I).poly(C). Strong stability of the polynucleotides against heat strand separation characterises the binding. Non-electrostatic component had larger share in parsing of the standard molar Gibbs energy of the binding. The processes' negative change in heat capacity is evidence of how essential hydrophobic forces are. Release of water molecules which are in random orientation mode occurs from RNA's hydrophobic binding pockets. Negative enthalpy and positive entropic change are the two significant features in this hydrophobic binding scenario. Another vital result of enthalpy-entropy compensation has been identified with the binding processes. The findings bear direct and ubiquitous acknowledgement in revitalizing our interest and broadening our horizon towards successful targeting of small molecules to RNAs.

Methylene blue adsorption on vanadium pentoxide nanorods dispersed in starch-grafted polyacrylonitrile

A brand-new vanadium pentoxide (V2O5) functionalized starch (St) grafted poly(acrylonitrile) (PAN) adsorbent was synthesized via microwave-assisted graft polymerization method to remove methylene blue dye from water. FTIR, TEM, SEM, and XRD analysis were used to characterize the materials. Experiments on batch adsorption were conducted on the V2O5 and V2O5-St-g-PAN composite. The most significant removal efficiency of methylene blue (MB) by V2O5-St-g-PAN in water was 90% at a pH of 9 with an optimum adsorbent dose of 0.2 g in a 50 mL of 50 mg/mL MB concentration. The adsorption mechanism followed the Langmuir isotherm model with a correlation coefficient (R2) of 0.9996. The adsorption of MB onto V2O5-St-g-PAN was thermodynamically favorable at all temperatures (ΔGo = −56.371 KJ/mol to −56.164 KJ/mol). A negative enthalpy change (ΔHo) of −60.482 KJ/mol and a positive entropy change (ΔSo) of +0.0138 KJ/mol indicates an exothermic and highly ordered adsorption process.

A novel Chitosan-Barbituric acid hydrogel supersorbent for sequestration of chromium and cyanide ions: Equilibrium studies and optimization through RSM

The objective of this study is to transform chitosan biopolymer by crosslinking with barbituric acid into an amine-rich product that could be applied as a water treatment agent. Chitosan-barbituric acid (CBA) was synthesized by lyophilization process and characterized using FT-IR, XRD, TGA-DTA, SEM-EDX, BET surface area and BJH pore size distribution analysis. The pHpzc was found to be 7.7 indicating applicability towards both cations and anion adsorption. The CBA was used for seizure of CrVI and CN– from aqueous solutions in batch adsorption as well as fixed bed column experiments. Response surface methodology (RSM) was used as a statistical tool to optimize the functioning parameters resulting in more than 90 % removal of these ions. As shown by isotherm and kinetics data, Langmuir isotherm and pseudo second order kinetics exhibited a good fit for the adsorption process. The maximum adsorption capacities of CBA towards CrVI and CN– evaluated using Langmuir isotherm fitment were 534.75 mg g−1 and 251.66 mg g−1 at pH 4.0 and 6.0 respectively. Thermodynamic studies indicated spontaneous and enthalpy driven course with large negative enthalpy changes of −56.39 and −31.81 kJ mol−1 respectively. Fixed bed column studies showed that the material could be used for larger sample volume treatment even at 200 mg/L CrVI and 100 mg/L CN−1 concentration. Regeneration studies of adsorbent was conducted over five adsorption–desorption cycles with removal efficiency more than 50 %indicating reusability of the adsorbent. Analysis of adsorbent sustainability revealed that the synthesis was eco-friendly as indicated by low value of E-factor of 0.32.

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.

Mechanistic investigation into the binding property of Yohimbe towards natural polymeric DNAs

DNA interactions with multivalent ligand(s) have increasingly become the subject of substantial research. For several small molecules with therapeutic potential, nucleic acids serve as their primary molecular target. Such interaction has been shown to affect transcription or replication, ultimately leading to apoptotic cell death. As a result, researchers are becoming increasingly interested in understanding how small molecules interact with DNA making it possible to develop new, DNA-specific drugs. The bioactive indole alkaloid, Yohimbe (Yohimbine; Yh) has been broadly studied in pharmacological properties while its binding mode to DNA has not been explicated so far. This study adopted molecular modelling and multi-spectroscopic methods to investigate the interaction between Yohimbine and herring testes (HT DNA) in physiological conditions. Minor hypochromic and bathochromic shifts of fluorescence intensity were observed, suggesting the binding of Yh to HT DNA. The Scatchard plot analyses using the McGhee-von Hipple method revealed non-cooperative binding and affinities in the range of 105 M−1. The thermodynamic parameters suggested exothermic binding, which was favoured by negative enthalpy and positive entropy changes from temperature-dependent fluorescence experiments. Salt-dependent fluorescence suggested that the interaction between the ligand and DNA was governed by non-polyelectrolytic forces. The results of iodide quenching, urea denaturation assay, dye displacement, and in silico molecular docking, suggested groove binding of Yh to HT DNA. Thus, the groove binding mechanism of interaction was validated by both biophysical and computational techniques. The structural elucidation and energetic profiling of Yh's interaction with naturally occurring polymeric DNA can be useful to the development of DNA-targeted therapeutics.

DFT study of SCN− adsorption effect on structural and electronic properties of Si12C12 fullerenes

Utilizing density functional theory (DFT) calculations, the adsorption characteristics and electronic structure of thiocyanate anion (SCN−) through nitrogen and sulfur heads upon the Si12C12 surface were investigated by the B3LYP functional and 6–31 + G** standard basis set. The results express that the covalent interaction of SCN− through the nitrogen head (−3.08 eV) is stronger in comparison with the sulfur head of SCN− (−2.32 eV) to the fullerene surface. Additionally, the interaction of two SCN− through nitrogen head has weaker surface adsorption on the silicon-carbon (SiC) atom (−1.27 eV) in comparison with the SiSi atom (−2.78 eV) of Si12C12 fullerene. The influence of SCN− adsorption on the Si12C12 surface was characterized by the infrared (IR) absorption spectrum. A significant orbital hybridization between SCN− and Si12C12 fullerenes occurred during the adsorption process, according to the computed density of states (DOS). According to the analysis of binding energy, energy gap, and dipole moment, Si12C12 fullerene can be applied to SCN− removal applications. Based on the thermodynamic parameters, the negative Gibbs free energy (ΔG) and enthalpy change (ΔH) values confirmed that the SCN− adsorption by the nitrogen heads on the Si12C12 surface was spontaneous and exothermic.

Spectroscopic study and molecular simulation: Bovine serum albumin binding with anticancer Pt complex of amyl dithiocarbamate ligand

Until now, many methods have been proposed to treat cancer, such as radiation therapy and drug therapy, but none of them have caused a complete cure for cancer. Heavy metal complexes such as cisplatin are among the compounds used as drugs in chemotherapy against cancer cells. These compounds cause cell death and have anti-cancer properties, but they have side effects. The biochemical mechanism of cisplatin is related to its interaction with DNA through covalent binding. To reduce the toxicity of metallodrugs, new complexes can be designed containing S, S- bidentate ligands such as diethyldithiocarbamate. Moreover, anti-cancer compounds probably interact with proteins, such as HSA, before passing the cancerous cell membrane and DNA as a target. So, the function of proteins and their stabilities are expected to change. In this research, the mode of binding of [Pt (bpy) (amyl.dtc)]NO3 complex with BSA was evaluated by various thermodynamic methods. Negative binding enthalpy and entropy changes amounts show that the connection between the Platinum compound and BSA occurs via the van Der Waals type of hydrogen bond. The negative Gibbs free energy change was obtained through isothermal titration, which showed interaction proceeds spontaneously. Moreover, the emission titration data showed that protein fluorescence quenching by platinum agent titration is static. Binding, quenching constants, and binding site number were obtained by the Stern-Volmer equation, and only one binding site was determined for this interaction. A Scatchard plot with a positive slope shows the Pt agent-BSA formation is proceeding positively cooperative. The kinetic study displayed that the absorption monitoring followed the second-order model. Finally, molecular docking simulation showed that the position of the Pt agent on protein is placed I under region II.

Comprehensive study of the kinetics of combustion and pyrolysis of petrochemical sludge: Experimentation and application of artificial neural network

Energy can be obtained from the pyrolysis and combustion of purified terephthalic acid (PTA) sludge which is produced during the treatment of PTA wastewater. In this study, the combustion and pyrolysis behaviors and kinetics of the sludge produced from the thermochemical treatment of PTA wastewater were analyzed under non-isothermal heating. It was found that reaction orders were in the range of 1–3 for oxidation/combustion. The reactions were exothermic, as indicated by the negative change in enthalpy. The phenomenon of auto gasification was observed during pyrolysis for three sludges. The analysis of the change of activation energy with the degree of conversion showed that several parallel reactions occurred at the beginning of the sludge decomposition during air combustion. The value of activation energy for CuSO4, FeCl3 and FeCl3 + CPAA sludge was 99.5 kJ/mol, 109 kJ/mol and 118.7 kJ/mol, respectively, for pyrolysis and 116.3 kJ/mol, 68.8 kJ/mol, and 127.9 kJ/mol, respectively, for combustion. These sludges are promising for energy recovery because they have a high net calorific value (NCV) and a high gross calorific value (GCV). The GCV was 22.4 MJ/kg, 19.8 MJ/kg, and 28.4 MJ/kg for CuSO4, FeCl3, and FeCl3 with CPAA, respectively and the NCV was 22.3 MJ/kg, 18.6 MJ/kg, and 27.3 MJ/kg for CuSO4, FeCl3, and FeCl3 with CPAA, respectively. The artificial neural network was used to validate the experimental results. The correlation coefficient between the expected and experimental results were 0.9945, 0.9980 and 0.9980 for CuSO4, FeCl3 and FeCl3 +CPAA sludge for pyrolysis, respectively and 0.9989, 0.9963 and 0.9968 for CuSO4, FeCl3 and FeCl3 +CPAA sludge for combustion, respectively. The developed ANN model successfully predicts the combustion and pyrolytic process for petrochemical sludge under specified conditions.

New insights into self-structure induction in poly (rA) by Quinacrine through non-classical intercalation: Spectroscopic and theoretical perspectives

Self-structure induction in a single stranded polyriboadenylic acid [poly (rA)] is an auspicious physiological phenomenon which switches off protein production in tumor cells. In the present study, the self-structure induction process in poly (rA) moiety was thoroughly investigated using various steady state and time resolved techniques. Optical melting pattern directly evidenced the formation of self-structured assembly in single stranded poly (rA) upon complexation with quinacrine. Further, UV-absorption spectroscopic studies revealed that quinacrine binds to poly (rA) in co-operative fashion and the indication of intercalative mode of binding first came out with the involvement of around two base pairs of poly (rA) in the complexation. Experimental observations established the unconventional or non-classical intercalation of quinacrine molecule inside self-structured duplex poly (rA) moiety. This complexation was accompanied with negative enthalpy change and positive entropy change; suggesting strong van der Waals and the H-bonding interactions as the major governing forces in the complexation. Moreover, ionic strength dependent binding study established that the non-polyelectrolytic forces were the dominating forces. Further, the photo physical behavior of QN was authenticated using time dependent density functional theory (TDDFT) where both the ground and excited states were exploited.

Acid-base treatment of lightweight expanded clay aggregate (LECA) for removal of paraquat from aqueous media

This study focuses on the modification of lightweight expanded clay aggregate (LECA) with sulfuric acid, potassium hydroxide, and sulfuric acid-potassium hydroxide to enhance the removal efficiency of the highly hazardous herbicide (paraquat) from the aqueous solution. The modification results showed that samples activated with sulfuric acid before KOH yielded higher removal efficiency (70.8%) than those activated with acid or base (25.6% and 35.8%, respectively). The paraquat uptake mechanism by LECA was investigated using XRD, XRF, FTIR, FESEM, BET, and zeta potential measurements. Batch adsorption tests were conducted under different conditions using LECA and acid-base-modified LECA. The results indicated the maximum removal efficiency for PQ at 240 min contact time, adsorbent dose of 3.5 g L−1, and pH 9 was achieved with the acid-base treated sample. Experimental data were evaluated with different isothermal, thermodynamic, and kinetic models. The pseudo-second-order model with a correlation coefficient of R2 > 0.99 was congruent with experimental results for LECA and acid-base-activated LECA through kinetic investigations. The highest adsorption capacities for the LECA and acid-base-activated LECA samples, respectively, were 6.12 mg g−1 and 21.23 mg g−1 according to the Langmuir equilibrium isotherm, which offered greater agreement with the experimental results. A negative standard enthalpy change (−21.09 kJ mol−1) and Gibbs free energy change for PQ uptake at 15, 25, and 35 °C indicated an exothermic and spontaneous process. Reusability studies confirmed that the treated adsorbent could successfully remove paraquat even after four regeneration cycles.