Values Of ΔH Research Articles

Flax fiber based semicarbazide biosorbent for removal of Cr(VI) and Alizarin Red S dye from wastewater

In the present study, flax fiber based semicarbazide biosorbent was prepared in two successive steps. In the first step, flax fibers were oxidized using potassium periodate (KIO4) to yield diadehyde cellulose (DAC). Dialdehyde cellulose was, then, refluxed with semicarbazide.HCl to produce the semicarbazide functionalized dialdehyde cellulose (DAC@SC). The prepared DAC@SC biosorbent was characterized using Brunauer, Emmett and Teller (BET) and N2 adsorption isotherm, point of zero charge (pHPZC), elemental analysis (C:H:N), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. The DAC@SC biosorbent was applied for the removal of the hexavalent chromium (Cr(VI)) ions and the alizarin red S (ARS) anionic dye (individually and in mixture). Experimental variables such as temperature, pH, and concentrations were optimized in detail. The monolayer adsorption capacities from the Langmuir isotherm model were 97.4 mg/g and 18.84 for Cr(VI) and ARS, respectively. The adsorption kinetics of DAC@SC indicated that the adsorption process fit PSO kinetic model. The obtained negative values of ΔG and ΔH indicated that the adsorption of Cr(VI) and ARS onto DAC@SC is a spontaneous and exothermic process. The DAC@SC biocomposite was successfully applied for the removal of Cr(VI) and ARS from synthetic effluents and real wastewater samples with a recovery (R, %) more than 90%. The prepared DAC@SC was regenerated using 0.1 M K2CO3 eluent. The plausible adsorption mechanism of Cr(VI) and ARS onto the surface of DAC@SC biocomposite was elucidated.

Impact of host-guest complexation between norfloxacin and -cyclodextrin on fluorescence quenching: Steady-state and time resolved fluorescence study

The behaviour of host-guest interaction of the drug i.e. Norfloxacin (NFX) with β-Cyclodextrin (β-CD) has been investigated by the fluorescence quenching method in acidic and neutral pH using copper as a quencher at various temperatures. The stoichiometry of the host-guest complication has been estimated using the Benesi−Hildebrand relationship. The incorporation of NFX inside the cavity of β-CD is revealed by fluorescence anisotropy and fluorescence lifetime measurements. The effect of temperature on the Stern-Volmer quenching constant (KSV) and binding constant (K) has been analyzed, and the type of quenching was confirmed from the fluorescence lifetime measurement. Using van’t-Hoff equation and Gibbs-Helmholtz equation, thermodynamic parameters like change of enthalpy (ΔH), entropy (ΔS) and free energy (ΔG) have been determined. The negative value of ΔH and the positive value of ΔS validate the hydrophobic interaction between drug and quencher, and the negative value of ΔG suggests that the complex is spontaneous in nature.

The Key Features of Catechols and α,β Unsaturated Carbonyl Moieties: Interaction With α‐syn Hydrophobic peptide and Activation of Catecholamines Pathway in Cells

AbstractParkinson's disease (PD) is the second most prevalent neurodegenerative disorder worldwide, and the treatment focuses on delivering L‐DOPA. In this work, we isolated and tested several compounds against α‐synuclein and the hydrophobic peptide 71VTGVTAVAQKTV82 including flavonols (kaempferol, quercetin, and isorhamnetin), isoflavone (genistein) and flavone (luteolin), and compounds with α, β unsaturated carbonyl moieties such as chlorogenic acid and the depsidone fumarprotocetraric acid. Most compounds inhibit both α‐synuclein and hydrophobic peptide fibrillization. Moreover, ITC experiments showed a Kd varying from 9 to 20 μM, and ΔH values vary from −1.94 to −10.5 among the compounds. Docking experiments showed the intermolecular interactions within the sites 2, 9, and 3/13 of α‐synuclein, and with the hydrophobic peptide. In cultured cells, the presence of the compounds showed that most of them can promote cell proliferation and differentiation. Considering that treatments for neurodegenerative disorders, including PD, is only palliative the evaluation of these compounds that can prevent the fibrillization of α‐synuclein and stimulate the catecholamines pathway is promising.

Changes of gelation behavior, water distribution and digestibility of protein-starch mixtures in the oat dough/batter model affected by water

The interactions between protein and starch in the oat dough/batter system during heating are particularly important for oat-based products but are rarely understood. In this study, the gelation behaviors and digestibility of oat protein-oat starch mixtures after heat treatment and their gelling properties in the oat dough/batter model corresponding to water content ranging from 50% to 80% were determined. Under the same water content, the oat protein-starch samples exhibited higher G′ and G″ values during the gelatinization process and lower gelatinization enthalpy (ΔH) than the oat starch samples. At low water content (oat dough system), competitive hydration between oat protein and starch played a dominant role, and protein inhibited the retrogradation behavior of starch. When the water content increased to 80% (oat batter system), the protein significantly promoted starch retrogradation behavior with ΔH values increasing from 0.54 to 1.71 J/g. The addition of protein weakened the tight binding between starch and water molecules and enhanced the mobility of water in the system. The interaction between oat protein and starch inhibited the enzymatic hydrolysis and slowed starch digestion, which was mainly related to the formation of resistant starch in the oat protein-starch gels system.

Co-Pyrolysis for Pine Sawdust with Potassium Chloride: Insight into Interactions and Assisting Biochar Graphitization.

This effort aimed to explore the activation and catalytic graphitization mechanisms of non-toxic salts in converting biomass to biochar from the perspective of pyrolysis kinetics using renewable biomass as feedstock. Consequently, thermogravimetric analysis (TGA) was used to monitor the thermal behaviors of the pine sawdust (PS) and PS/KCl blends. The model-free integration methods and master plots were used to obtain the activation energy (E) values and reaction models, respectively. Further, the pre-exponential factor (A), enthalpy (ΔH), Gibbs free energy (ΔG), entropy (ΔS), and graphitization were evaluated. When the KCl content was above 50%, the presence of KCl decreased the resistance to biochar deposition. In addition, the differences in the dominant reaction mechanisms of the samples were not significant at low (α ≤ 0.5) and high (α ≥ 0.5) conversion rates. Interestingly, the lnA value showed a linearly positive correlation with the E values. The PS and PS/KCl blends possessed positive ΔG and ΔH values, and KCl was able to assist biochar graphitization. Encouragingly, the co-pyrolysis of the PS/KCl blends allows us to target-tune the yield of the three-phase product during biomass pyrolysis.

Metal ions recognition and DNA binding properties of four rosin derivatives

Four rosin derivatives containing amide, pyridine and dehydroabietyl sub-units were synthesized. Their selective and sensitive recognition of Cu2+ and Fe3+ ions were confirmed by UV–vis and fluorescence spectra. Their detection limits for Cu2+ and Fe3+ were lower than the maximum allowable levels of Cu2+ and Fe3+ in drinking water. They could displace ethidium bromide (EB) molecules inserted into CT DNA base pairs and induce fluorescence quenching of CT DNA-EB system in a static mode. The negative ΔG values proved that the binding processes of the compounds to CT DNA were spontaneous. The negative values of both ΔH and ΔS solidified that the hydrogen bonds or Van der Waals was the driving force for the interactions between the four compounds and CT DNA. Metal ion recognition and DNA interaction indicate that the number of pyridine rings and the flexibility of the compounds had influence on the strength of the above activities.

Preparation of Neohesperidin-Taro Starch Complex as a Novel Approach to Modulate the Physicochemical Properties, Structure and In Vitro Digestibility.

Neohesperidin (NH), a natural flavonoid, exerts multiple actions, such as antioxidant, antiviral, antiallergic, vasoprotective, anticarcinogenic and anti-inflammatory effects, as well as inhibition of tumor progression. In this study, the NH-taro starch complex is prepared, and the effects of NH complexation on the physicochemical properties, structure and in vitro digestibility of taro starch (TS) are investigated. Results showed that NH complexation significantly affected starch gelatinization temperatures and reduced its enthalpy value (ΔH). The addition of NH increased the viscosity and thickening of taro starch, facilitating shearing and thinning. NH binds to TS via hydrogen bonds and promotes the formation of certain crystalline regions in taro starch. SEM images revealed that the surface of NH-TS complexes became looser with the increasing addition of NH. The digestibility results demonstrated that the increase in NH (from 0.1% to 1.1%, weight based on starch) could raise RS (resistant starch) from 21.66% to 27.75% and reduce RDS (rapidly digestible starch) from 33.51% to 26.76% in taro starch. Our work provided a theoretical reference for the NH-taro starch complex's modification of physicochemical properties and in vitro digestibility with potential in food and non-food applications.

Physico-chemical and biological studies of some Copper(I) complexes in binary mixtures of polar solvents at variable temperature

Physico-chemical parameters like, conductance, viscosity, volumetric, thermo acoustic, thermodynamics of viscous flow, were thoroughly evaluated from the experimentally obtained data of specific conductance, viscosity, density, and ultrasonic velocity. These parameters were evaluated for Copper(I) nitrate complexes in binary mixtures of polar solvents, Dimethylsulfoxide (DMSO), Pyridine (Py), and Nitromethane (NM) at variable temperatures (298 K-318 K) and at 1 atmospheric pressure. Ionic B values were evaluated using Jones-Dole equation to determine the extent of molecular interactions. From the measured viscosity, using Erying's transition state theory, the thermodynamic parameters of viscous flow such as Gibb's energy of activation (ΔG)*, enthalpy of activation (ΔH)*, and entropy of activation (ΔS)* were also evaluated. The thermodynamic function showed the values of ΔH* as positive for all electrolytes and ΔS* as negative. From the conductance data, the Energy of Activation (Ea) and ionic walden product (λoη) were evaluated and tabulated. Further, in order to discover more about the solute–solvent interactions, limiting apparent molar volume (ɸ˚v), Masson’s coefficient (Sv), partial molar expansibilities (ɸ˚E) and Hepler’s constant were also calculated from density and velocity data at variable temperatures. Limiting apparent molar volume ɸ˚v values for both binary mixtures were positive, indicating strong solute–solvent interactions. Thermo acoustical parameters like internal pressure (πi), Rao’s constant (Rm) and Wada’s constant (W) were also evaluated. The results from all the studies showed the possible solvation in DMSO + Py solvent mixture as compared to DMSO + NM system. Further, the copper(I) nitrate complexes with bioactive ligands were tested against Gram positive strains (S mutans MTCC 497 and S aureus MTCC 7443), Gram negative strains (S enteric MTCC 164 and P aeruginosa MTCC 4673) and fungus (A parasiticus NCIM 696, Candida albicans MTCC 183 and A niger NCIM 501). The zone of inhibition was also measured for the complexes. All the complexes with potential bioactive ligand containing Nitrogen and Sulphur atom bonded to central copper atom showed antibacterial and antifungal activity.

Kinetic and thermodynamic evaluations of oil extraction from immobilized Chlorella vulgaris using different solvents

Investigating the effect of different solvents used for microalgae oil extraction on the determinations of kinetic values and thermodynamic parameters is a compelling novel approach for the current study. The primary concern of microalgae oil extraction is selecting a solvent system because it has a massive influence on the extraction yield, composition, and oil quality. Three different solvent systems were inspected to determine the suitable solvent for the oil extraction from immobilized Chlorella vulgaris: heptane, heptane:methanol, and heptane:ethanol. The research methodology begins with the immobilization of microalgae cells. The matured immobilized beads were then harvested, and dried biomass was recovered. The oil was extracted by solvent extraction method using the solvents mentioned. Finally, the extracted oil was trans-esterified and analyzed for fatty acid methyl ester profile. Based on the results calculated, heptane is determined to extract the most oil with 27.42 %, followed by H:M and H:E at the highest temperature and longest running time. When the polar solvent is mixed with a non-polar solvent, the mixture has the least kinetic value and immense activation energy. However, the activation energy for heptane is only 89.06 kJ/mol. Another essential objective of this research is to determine the effects of solvents on the thermodynamics parameters. The extraction process of microalgae oil using heptane alone is determined to have a ΔH value of 0.111 kJ/mol, followed by 0.201 and 0.102 kJ/mol for solvent system H:M and H:E respectively. All the values obtained are positive, thus making the extraction processes using various solvents to be endothermic. The positive values of ΔS and the negative values of ΔG indicated that the oil extraction using heptane is thermodynamically spontaneous and irreversible, thus making it economically feasible. The fatty acids methyl esters such as palmitic, stearic, oleic, linoleic, and linolenic were the prime constituents quantified in the oil extracted using heptane compared to other solvent systems. Therefore, with the larger and increasing kinetic values and lowest activation energy, it can be concluded that heptane is the most suitable solvent for the oil extraction of immobilized Chlorella vulgaris compared to other solvent systems employed in the current research work.

Kinetic and thermodynamic aspects on the interaction of serum albumin with sodium hydrosulfite: Spectroscopic and molecular docking methods

Sodium hydrosulfite is a sulfur-containing food additive that is used as a decolorizing agent in the sugar industry to purify syrup and remove natural color compounds obtained from sugar beet, sugar cane, and color compounds created during production. Recent studies show gastrointestinal, aspiration, skin and eye complications from excessive use of sulfur-containing compounds. According to recent studies and the importance of investigating the interaction of food additives with biological molecules, we also investigated the binding properties of sodium hydrosulfite to blood serum albumin through UV–Vis spectroscopy, fluorescence spectroscopy, competitive binding experiments, Fourier transform infrared spectrometry (FT-IR), surface plasmon resonance (SPR), and molecular simulation analysis. According to the results, Sodium hydrosulfite decreased the fluorescence intensity of BSA through both static and dynamic quenching mechanisms after forming a complex with BSA. The results of synchronous fluorescence and FT-IR demonstrated that the microenvironment and the secondary structure of BSA were changed in the presence of sodium hydrosulfite. The negative values of ΔH° and ΔS° indicated that van der Waals force or hydrogen bonding is the main factor of binding between sodium hydrosulfite and BSA. The result of UV–Vis spectroscopy confirmed the binding of sodium hydrosulfite to BSA. Binding constant decreases from 13.06 to 0.24 (103 M−1) with increasing temperature, which indicates a decrease in complex formation owing to the interaction of sodium hydrosulfite with BSA. Molecular docking experiments confirm the binding tendency of sodium hydrosulfite to a cavity between domains II and III (Site I and Site II) through residues Cys460, Cys476, Asn457, Arg483, Lys204, and Ala200 with a binding energy of −12.86 kJ mol−1.

Green synthesis of Fe3O4@SiO2@Salg particles for organophosphorus pesticides removal: Mechanisms, biosafety, and application

A biosafe magnetic Fe3O4@SiO2@Salg (GMS) was successfully developed via a simple and economic method. Fe3O4@SiO2 particles were selected as the magnetic core, and they directly interacted with sodium alginate, thus mitigating the use of cross-linking agents. The microstructure, properties, and formation mechanism of GMS were examined using FE-SEM, TEM, VSM, TGA, zeta potential, and FT-IR. The as-developed GMS was used as a desirable adsorbent to remove organophosphorus pesticides (OPPs) from water bodies, and the influence of different factors on the removal efficiencies of OPPs was investigated. Optimal preparation conditions were determined, and the excellent removal efficiencies of the 18 OPPs were achieved in this study (80.5%–100% for tap, river, and seawater). After the GMS was recycled eight times, the removal efficiencies of 18 OPPs were maintained at >80%. Adsorption kinetics and isotherm models showed that the adsorption process was accurately fitted with the Langmuir isotherm and pseudo-second-order models. The values of ΔG, ΔH, and ΔS were negative, indicating that the OPPs were adsorbed on the GMS spontaneously via an exothermal reaction, and chemisorption was the dominant adsorption mechanism. Overall, the as-developed GMS was biosafe as revealed by cytotoxicity experiments. GMS had good environmental security, stability, and reusability, and it exhibited excellent potential for removing OPPs from aqueous solutions without causing secondary pollution.

Analysis of the Binding Mechanism of Bioactive Coumarins with Ovalbumin: Further Investigation into the Inhibitory Effects toward Protein Fibrillation

Two bioactive coumarin derivatives, 7-hydroxycoumarin (7-HC) and 4-methyl-7-hydroxycoumarin (4-Me-7-HC), were used to investigate the molecular interactions with the main food allergen from egg white, ovalbumin (OVA), along with their inhibitory effects on OVA aggregation. The mechanism of binding interaction was elucidated by multispectroscopic and computational methods. Circular dichroism (CD) and Fourier transform infrared (FT-IR) experiments confirmed the ligand-induced conformational changes of OVA. The fluorescence spectroscopic experiments demonstrated that the quenching mechanism was an unusual static quenching method with binding constants (Kb) in the range of 104 M–1, indicating a moderate nature of binding between OVA and coumarins. Thioflavin T (ThT) and Congo red (CR) binding assays confirmed the production of OVA fibrils, and the aggregation was shown to be inhibited by the coumarin derivatives in vitro. Thermodynamic parameters for OVA-7-HC/4-Me-7-HC interactions showed positive ΔH and ΔS values, indicating hydrophobic forces predominated in the binding processes and a negative ΔG value, implying the spontaneity of the complex formation, which was then further confirmed by computational studies.

Mechanistic investigation of pyrolysis kinetics of water hyacinth for biofuel employing isoconversional method

The current study employs non-isothermal thermogravimetric analysis to analyze the thermal degradation behavior of water hyacinth (WH), with the primary goal of determining the kinetic triplet. The pyrolysis of water hyacinth achieved approximately 80% thermal degradation during three phases of breakdown at temperatures ranging from 30 to 900 °C. The activation energy of feedstock breakdown was calculated using four different model-free approaches i.e., Flynn-Wall- Ozawa (FWO), Starink, Friedman, and Kissinger- Akahira-Sunose (KAS), with mean values ranging from 251.33 to 298.48 kJ/mol inside the conversion band of 0.15–0.75. The Master plot results depicted that for conversion (α) ≤ 0.5, the biomass degradation followed a two-dimensional process of diffusion. For α ≥ 0.5, the response, however, is adequately described by growth processes and nucleation. The values of excitation energy estimated using isoconversional techniques were also utilized to determine various thermodynamic parameters. From the thermodynamic study, the mean value of ΔH was 293.66 kJ/mol, suggesting that the generation of activated complex is simpler since the potential energy barrier is lower. A high ΔS value indicates increased reactivity and less time required to synthesize the activated compound. In conclusion, the characterization and kinetic analyses of biomass reveal their potential as pyrolysis feedstock.

Effective Adsorptive Removal of Coomassie Violet Dye from Aqueous Solutions Using Green Synthesized Zinc Hydroxide Nanoparticles Prepared from Calotropis gigantea Leaf Extract

The removal of color from dye wastewater is crucial, since dyes are extremely toxic and can cause cancer in a variety of life forms. Studies must be done to use cost-effective adsorbents for the removal of color from dye effluents to protect the environment. To our knowledge, virtually no research has been done to describe the possibility of using Calotropis gigantea leaf extract zinc hydroxide nanoparticles (CG-Zn(OH)2NPs) as an adsorbent for the decolorization of Coomassie violet (CV) from the aqueous emulsion, either in batch mode or continuously. In the present batch investigation, CV dye is removed from the synthetic aqueous phase using CG-Zn(OH)2NPs as an adsorbent. The synthesized nanoparticles were characterized using various instrumental techniques such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS) and Brunauer–Emmett–Teller (BET) surface area and pore volume, a particle size analyser, and zero-point charge. The decolorization efficacy of CV dye from an aqueous phase by the adsorbent was examined in batch mode by varying process parameters. The consequences of various experimental variables were optimized using response surface methodology (RSM) to achieve the maximum decolorization efficiency (90.74%) and equilibrium dye uptake, qe (35.12 mg g−1). The optimum pH, dye concentration, CG-Zn(OH)2NPs adsorbent dosage, and particle size were found to be 1.8, 225 mg L−1, 5 g L−1, and 78 μm, respectively for CV dye adsorption capacity at equilibrium. The adsorbent zero-point charge was found to be at pH 8.5. The Langmuir isotherm model provided a good representation of the equilibrium data in aqueous solutions, with a maximum monolayer adsorption capability (qmax) of 40.25 mg g−1 at 299 K. The dye adsorption rate follows a pseudo-second-order kinetic model at various dye concentrations, which indicated that the reaction is more chemisorption than physisorption. The negative values of ΔG and positive values of ΔH at different temperatures indicate that the adsorption process is spontaneous and endothermic, respectively. Reusability tests revealed that the prepared nanoparticles may be used for up to three runs, indicating that the novel CG-Zn(OH)2NPs seems to be a very promising adsorbent for the removal of Coomassie violet dye from wastewater.

Comparison of different ultrafiltration-recovered soy protein hydrolysate fractions and their effects on the stability of mulberry anthocyanin extract

The effects of three ultrafiltration-recovered soy protein hydrolysate fractions (USHFs) with different molecular weights (>10 kDa for USHF-1, 1–10 kDa for USHF-2, and ＜1 kDa for USHF-3) on mulberry anthocyanin extract (MAE) was investigated under the condition of neutral pH for the first time in this study. Generally, all USHFs showed pronounced color- and anthocyanin-stabilized effects. The addition of 1 mg/mL of USHF-3 showed best protection for anthocyanin stability in this study. Based on the spectroscopic results, the electrostatic interactions were the main forces in the binding system between USHF-3 and cyanidin-3-O-glucoside (C3G) indicated by the negative ΔH and positive ΔS values. USHF-1 and USHF-2 and their complexes with C3G were mainly driven by hydrophobic interactions determined with positive ΔH and positive ΔS values. C3G addition resulted in tertiary structural changes of the USHFs. Overall, the complexation of USHFs and C3G participates in maintaining anthocyanin stability.

Reaction-assisted separation of acetone from the azeotrope of methanol and acetone

The separation of methanol–acetone azeotrope has been a challenging issue. Methanol in the azeotrope was selectively transformed and removed in this paper. Under mild conditions, 95.5% of methanol was transformed into methyl phenylcarbonate (MPC), phenol and dimethyl carbonate (DMC), while acetone was not converted. The separation process of reaction products was simulated, and 99% of acetone with purity of 99.3 wt% was recovered. The byproducts phenol and DMC were also recovered with purity of 93 and 76 wt%, respectively. Compared to the typical pressure-swing and extractive-distillation schemes, the total number of theoretical stages and heat duty could be reduced by 27.7–38.3% and 48.6–58.4%, approximately. The results of thermodynamic experiments showed that the apparent equilibrium constant (124.4 at 23.1 °C) in the first step was much larger than that (12.9) in the second step, indicating that the intermediate MPC was very stable, and thermodynamic factors originating from the specific coplanar structure of substrate contributed to the high methanol conversion. The transesterification reactions were endothermic and spontaneous due to the positive ΔH and negative ΔG values. The spontaneity of reactions was attributed to the increase of entropy, for which the reason was the more possible spatial distributions of atoms in the products. This paper is beneficial for the separation of alcohols from various aprotic solvents.

Surface equilibrium and thermodynamics implications of the corrosion inhibition of mild steel in acid medium using quinine inhibitor

One problem faced by industries is the degradation of their metal pipes and machine parts which are exposed to chemically aggressive media. This has necessitated the search for cheap and non-toxic substances that can limit corrosion. The inhibition potential of quinine against the corroding of mild steel in 1M HCl medium was tested under varied concentration of quinine and temperature, using gravimetric method. The results showed that corrosion rate and weight loss decreased with increasing concentration of quinine and temperature up to 40 °C, while surface coverage, θ, and inhibition efficiency IE, increased as the concentration and temperature increased. Surface equilibrium studies showed that the inhibition action followed the Freundlich isotherm with value of adsorption intensity that suggests a cooperative adsorption mechanism in heterogeneous sites while thermodynamic analysis implied that the process of inhibition was endothermic having a positive value of ΔH (17.384 kJ mol-1), enthalpy-driven with a negative ΔS (-64.434 kJ mol-1K-1) and occurred by a physisorption mechanism. Positive ΔG obtained at the studied temperatures suggests that the corrosion process was rendered passive and unfeasible. These findings project quinine as a promising inhibitor for chemical degradation of mild steel in hydrochloric acid medium.

Cytotoxic activity of Ru(II)/DPEPhos/N,S-mercapto complexes (DPEPhos = bis-[(2-diphenylphosphino)phenyl]ether)

We report here on three new ruthenium(II) complexes, [Ru(DPEPhos)(mtz)(bipy)]PF6 (Ru1), [Ru(DPEPhos)(mmi)(bipy)]PF6 (Ru2) and [Ru(DPEPhos)(dmp)(bipy)]PF6 (Ru3). DPEPhos = bis-[(2-diphenylphosphino)phenyl]ether, mtz = 2-mercapto-2-thiazoline, mmi = 2-mercapto-1-methylimidazole, dmp = 4,6-diamino-2-mercaptopyrimidine and bipy = 2,2′-bipyridine. The compounds were characterized by several spectroscopic techniques, and the molecular structure of Ru1 complex was determined by single-crystal X-ray diffraction. The cytotoxicity of Ru1 – Ru3 complexes were tested against the A549 (human lung) and the MDA-MB-231 (human breast) cancer cell lines and against MRC-5 (non-tumor lung) and MCF-10A (non-tumor breast) cell lines through the MTT assay. All three complexes are cytotoxic against the cell lines studied, with IC50 values lower than those found for the cisplatin. Among them, the Ru2 complex has shown the best selectivity against MDA-MB-231 cancer cell lines, with an IC50 value 12 times lower than that on MCF-10A. The complex Ru2 was capable to induce changes in MDA-MB-231 cells morphology, with loss of cellular adhesion, inhibited colony formation and induce an accumulation of cells at the sub-G1 phase, with an increase in S-phase and decrease of cells at G2 phase. Viscosity, electrochemical and Hoechst 33258 displacement experiments for Ru1 – Ru3 complexes with calf thymus DNA (CT-DNA) showed an electrostatic and groove binding mode of interaction. Additionally, the complexes interact with the protein Human Serum Albumin (HSA) by static mechanism. The negative values for ΔH and ΔS indicate that van der Waals forces and hydrogen bonding may occurs between the complexes and HSA. Therefore, this class of complexes are promising anticancer candidates and may be selected to further detailed studies.

Iron response elements (IREs)-mRNA of Alzheimer's amyloid precursor protein binding to iron regulatory protein (IRP1): a combined molecular docking and spectroscopic approach

The interaction between the stem-loop structure of the Alzheimer's amyloid precursor protein IRE mRNA and iron regulatory protein was examined by employing molecular docking and multi-spectroscopic techniques. A detailed molecular docking analysis of APP IRE mRNA∙IRP1 reveals that 11 residues are involved in hydrogen bonding as the main driving force for the interaction. Fluorescence binding results revealed a strong interaction between APP IRE mRNA and IRP1 with a binding affinity and an average binding sites of 31.3 × 106 M−1 and 1.0, respectively. Addition of Fe2+(anaerobic) showed a decreased (3.3-fold) binding affinity of APP mRNA∙IRP1. Further, thermodynamic parameters of APP mRNA∙IRP1 interactions were an enthalpy-driven and entropy-favored event, with a large negative ΔH (–25.7 ± 2.5 kJ/mol) and a positive ΔS (65.0 ± 3.7 J/mol·K). A negative ΔH value for the complex formation suggested the contribution of hydrogen bonds and van der Waals forces. The addition of iron increased the enthalpic contribution by 38% and decreased the entropic influence by 97%. Furthermore, the stopped-flow kinetics of APP IRE mRNA∙IRP1 also confirmed the complex formation, having the rate of association (kon) and the rate of dissociation (koff) as 341 μM−1 s−1, and 11 s−1, respectively. The addition of Fe2+ has decreased the rate of association (kon) by ~ three-fold, whereas the rate of dissociation (koff) has increased by ~ two-fold. The activation energy for APP mRNA∙IRP1 complex was 52.5 ± 2.1 kJ/mol. The addition of Fe2+ changed appreciably the activation energy for the binding of APP mRNA with IRP1. Moreover, circular dichroism spectroscopy has confirmed further the APP mRNA∙IRP1 complex formation and IRP1 secondary structure change with the addition of APP mRNA. In the interaction between APP mRNA and IRP1, iron promotes structural changes in the APP IRE mRNA∙IRP1 complexes by changing the number of hydrogen bonds and promoting a conformational change in the IRP1 structure when it is bound to the APP IRE mRNA. It further illustrates how IRE stem-loop structure influences selectively the thermodynamics and kinetics of these protein-RNA interactions.

Thermal degradation behaviour, kinetics, and thermodynamics of Bombax Malabarica seeds through TG-FTIR and Py-GC/MS analysis

The pyrolysis process kinetics, thermodynamics, and product analysis of Simal cotton (Bombax Malabarica) seeds, a non-edible biomass feedstock were performed to evaluate its suitability as an alternative renewable energy source. The active pyrolysis region of 220 to 600 °C was perceived with peak temperatures between 338.1 and 362.4 °C using TG analysis. The degradation of hemicellulose was observed at temperatures <300 °C and cellulose in the range of 300–400 °C. The effect of heating rate on the composition of evolved mixed gases and functional groups was evaluated using the TG-FTIR. The evolved typical gaseous products include H2O, CO, CO2, CH4, C = O, CO, HCN, and NH3. The order of the volatile pyrolysis products: acids > phenols > amines > aliphatics > alcohols > furans > aldehydes > nitriles > ketones > esters was determined using Py-GC/MS for higher selectivity of value-added products. The mean values of Ea, ΔH, ΔG, and ln(A) of feedstock were in the range of 181.1–193.8, 176.1–188.7, 180.6–190.1 kJ mol−1, and 27.1–34.1 min−1, respectively. The above experimental data could be used to design a process for bio-oil and bioenergy production from the seed.