Search

In this paper, new potentiometric, calorimetric, and voltammetric measurements are reported to model the behavior of d-gluconic acid in aqueous NaCl(aq) and NaNO3(aq) ionic media at different ionic strengths and temperatures (283.15 ≤ T/K ≤ 318.15) also in the presence of Sn2+ and Zn2+. The protonation constants of d-gluconic acid (Gluc- in its deprotonated form) in NaCl(aq) and NaNO3(aq) are very similar. The dependence on ionic strength of the protonation constant was modeled by means of the extended Debye-Hückel type equation, the Specific ion Interaction Theory (SIT) and a weak interaction model. At infinite dilution and T = 298.15 K, the thermodynamic parameters for the proton binding reaction, determined by direct calorimetric titrations and temperature gradients of protonation constants, are log KH0 = 3.709 ± 0.004, ΔG0 = −21.18 ± 0.01 kJ mol-1, ΔH0 = −4.56 ± 0.04 kJ mol-1, and TΔS0 = 16.6 ± 0.1 kJ mol-1, indicating that the reaction is exothermic and entropic in nature. Potentiometric and voltammetric measurements on the Sn2+ and Zn2+/Gluc- systems allowed us to determine the MGluc+ species for both systems at different ionic strengths, together with the Sn(Gluc)2 and Sn(OH)Gluc species. The values of the formation constant of the SnGluc+ species are higher than the corresponding ZnGluc+. During the experiments, the precipitation of insoluble species was evidenced at pH ≥ 4.0 for Sn2+/Gluc- and pH ≥ 7.0 for Zn2+/Gluc-. The stoichiometry of the precipitates was established by means of thermogravimetric analysis, and the solubility of the two salts, Sn(OH)Gluc(s) and Zn(Gluc)2(s), was determined in pure water, in NaCl and in NaNO3 aqueous media. In pure water, the total solubility is ST = 0.262 ± 0.001 and 0.082 ± 0.006 mol kg-1 for the ZnGluc2 and Sn(OH)Gluc, respectively. Calorimetric measurements were performed to determine the enthalpy changes of the gluconate protonation and Sn2+ complex formation constants at different ionic strengths. The effect of two anions, as fluoride and citrate, on the stability of the Sn2+/Gluc- species was studied by means of potentiometric measurements at I = 0.15 and 1.02 mol kg-1, and it was found that the formation of mixed complexes is thermodynamically favored. [ABSTRACT FROM AUTHOR]

Thiscontribution reports the results of an investigation on thespeciation of various lanthanoid(III) cations (Ln3), namely,La3, Nd3, Sm3, Eu3, Gd3, Dy3, and Yb3, in the presenceof reduced glutathione (or simply glutathione, GSH), in NaCl(aq)at I= 0.15 mol·dm–3and T= 298.15 K. GSH forms in all cases the same four species,namely, Ln(GSH)H3, Ln(GSH)H2, Ln(GSH)H, andLn(GSH)OH, whose stability depends on the type of lanthanoid, althoughit is also possible to consider an average stability for a genericlanthanoid, at least for the protonated species. Measurements at differenttemperatures and ionic strengths for the La3ﱤ and Gd3ﱤ systems have also been performed, to evaluate theireffect on the speciation of both GSH and the Ln3熫抢.The dependence of the determined stability constants on Iand Thas been modeled by an extended Debye–Hückeltype and by the van’t Hoff equations. In this last case, theformation enthalpy changes of La3ﱤ species have alsobeen determined. The stability constants obtained have been thereforeused to quantify the sequestering ability of GSH toward the investigatedcations, in different pH, ionic strength, and temperature conditions,by the calculation of several pL0.5parameters. Their analysisshowed that, generally, the sequestering ability of GSH increaseswith increasing pH and decreases with increasing temperature, whilethe ionic strength has only a small effect. Finally, results obtainedmay be exploited for the evaluation of the speciation (and, therefore,of the sequestration) of any Ln3熫抢 in the presenceof GSH in different conditions of Tand I, like those featuring many natural waters and biological fluids. [ABSTRACT FROM AUTHOR]

The hydrolysis of mixed-metal cations (Al3+/CH3Sn3+) was studied in aqueous solutions of NaNO3, at I = 1.00 ± 0.05 mol·dm–3 and T = 298.15 K, by potentiometric technique. Several hydrolytic mixed species are formed in this mixed system, namely, Alp(CH3Sn)q(OH)r with (p, q, r) = (1, 1, 4), (1, 1, 5), (1, 1, 6), (2, 1, 4), (1, 2, 5), (1, 4, 11), (1, 3, 8), and (7, 6, 32). The stability of these species, expressed by the equilibrium: pAl3+ + qCH3Sn3+ + rOH– = Alp(CH3Sn)q(OH)r3(p+q)–r, βpqrOH, can be modeled by the empirical relationship: log βpqrOH = −3.34 + 2.67p + 9.23(q + r). By using the equilibrium constant Xpqr relative to the formation reaction: pAl(p+q)(OH)r + q(CH3Sn)(p+q)(OH)r = (p + q)Alp(CH3Sn)q(OH)r, it was found that the formation of heterometal mixed species is thermodynamically favored, and the extra stability can be expressed as a function of the difference in the stability of parent homometal species. This leads, in turn, to a significant enhancement of hydrolysis and solubility. [ABSTRACT FROM AUTHOR]

The stability of M/Phy species (M = Ag+, CH3Hg+, Mn2+, Fe2+, Co2+, VO2+, and Phy = Phytate) was determined in NaNO3, at I= 0.10 mol·dm–3and T= 298.15 K, potentiometrically. For the VO2+/Phy system, the measurements were performed at differentionic strengths (to 0.45 mol·dm–3) and ionicmedia (NaNO3and Na2SO4). In general,the formation of six MHqPhy (with 0 ≤ q≤ 5) species was observed. For the CH3Hg+/Phy system, the formation of three polynuclear species,M2HqPhy (with 2 ≤ q≤ 4), was also evidenced. The general stabilitytrend is: VO2+∼ CH3Hg+>Co2+> Mn2+∼ Fe2+>Ag+. The sequestering ability of phytate toward the consideredmetal cations was evaluated at different pH values and increased withincreasing pH, except for methylmercury and vanadyl. Literature valueswere critically compared, where possible, with data reported in thiswork. The dependence of the formation constants of the MHqPhy species on the number of protons and on the firstmetal hydrolysis constants was modeled. Furthermore, a relationshipbetween the stability of the mononuclear MHqPhy and the polynuclear MpHqPhy species was found. These three relationshipswere then combined, for testing and predictive purposes. The lastcontribution of this research group to the series entitled “Speciationof phytate ion in aqueous solution” is reported in ref 1. [ABSTRACT FROM AUTHOR]

The hydrolysis of Al3+ was studied in aqueous 1 mol L-1 NaNO3 solution at different concentrations (20-200 mmol L-1) and temperatures (283.15 - 343.15 K) by potentiometry (ISE-H-, glass electrode). Many different speciation models were considered in the calculations and it was found that the best model is represented by the following species: Al(OH)2+, Al3(OH)45+, Al13(OH)327+. Hydrolysis constants and enthalpy changes at different temperatures are reported. [ABSTRACT FROM AUTHOR]

Abstract: The solubility of two dicarboxylic acids (COOH)–(CH2) n –(COOH) (n =4, 5; namely: adipic and pimelic acids, respectively) was determined in NaCl(aq) (0.5–4.5)molL−1, (CH3)4NCl(aq) (0.25–3)molL−1, (C2H5)4NI (0.25–1)molL−1 and in pure water, at t =25°C. The activity and Setschenow (k) coefficients of neutral species were calculated in all ionic media from solubility data. These coefficients, in NaCl ionic medium, were also calculated by distribution (2-methyl-1-propanol/aqueous solution) measurements. The solubility trend is (C2H5)4NI>(CH3)4NCl>NaCl. To fully characterize the acid–base behaviour of the dicarboxylic acids, the self-interaction (k i) parameters from solubility and distribution data and the dimerization constant (K D) from the protonation constants in the same experimental conditions, were calculated. From these data, together with solubility ones, Pitzer and SIT parameters were calculated. [Copyright &y& Elsevier]

The interactions of dopamine [2-(3,4-Dihydroxyphenyl)ethylamine, (Dop−)] with cadmium(II), copper(II) and uranyl(VI) were studied in NaCl(aq) at different ionic strengths (0 ≤ I/mol dm−3 ≤ 1.0) and temperatures (288.15 ≤ T/K ≤ 318.15). From the elaboration of the experimental data, it was found that the speciation models are featured by species of different stoichiometry and stability. In particular for cadmium, the formation of only MLH, ML and ML2 (M = Cd2+; L = dopamine) species was obtained. For uranyl(VI) (UO22+), the speciation scheme is influenced by the use of UO2(acetate)2 salt as a chemical; in this case, the formation of ML2, MLOH and the ternary MLAc (Ac = acetate) species in a wide pH range was observed. The most complex speciation model was obtained for the interaction of Cu2+ with dopamine; in this case we observed the formation of the following species: ML2, M2L, M2L2, M2L2(OH)2, M2LOH and ML2OH. These speciation models were determined at each ionic strength and temperature investigated. As a further contribution to this kind of investigation, the ternary interactions of dopamine with UO22+/Cd2+ and UO22+/Cu2+ were investigated at I = 0.15 mol dm−3 and T = 298.15K. These systems have different speciation models, with the MM'L and M2M'L2OH [M = UO22+; M' = Cd2+ or Cu2+, L = dopamine] common species; the species of the mixed Cd2+ containing system have a higher stability with respect the Cu2+ containing one. The dependence on the ionic strength of complex formation constants was modelled by using both an extended Debye–Hückel equation that included the Van't Hoff term for the calculation of the formation enthalpy change values and the Specific Ion Interaction Theory (SIT). The results highlighted that, in general, the entropy is the driving force of the process. The quantification of the effective sequestering ability of dopamine towards the studied cations was evaluated by using a Boltzmann-type equation and the calculation of pL0.5 parameter. The sequestering ability was quantified at different ionic strengths, temperatures and pHs, and this resulted, in general, that the pL0.5 trend was always: UO22+ > Cu2+ > Cd2+. [ABSTRACT FROM AUTHOR]

• The study improves the knowledge on the behaviour and thermodynamic properties of some biopolymers. • The variation of the constants in dependence on ionic strength has been modelled. • The binding ability of the polymers has been investigated towards Ca2+, Zn2+ and Sn2+. • The effect on the complexing ability of a secondary inorganic ligand has been evaluated. • The sequestering ability of the polymers towards the metal cations has been evaluated by the pL 0.5. The aim of this paper is to enhance the knowledge on the behaviour and thermodynamic properties of natural and synthetic biopolymers in aqueous solutions. The acid-base properties of Carrageenan (Car), Xanthan gum (XG), Hydroxyethyl cellulose (HEC), Carboxymethyl cellulose (CMC), Acusol 445™ (Sol), Monopropylene glycol (MPG) and Polyethylene glycol (PEG) have been studied by potentiometric technique in NaNO 3(aq) , at I = 0.15 mol dm−3 and T = 298.15 K. In some cases, the protonation constants have been determined at different ionic strengths, and the dependence on ionic strength has been modelled by a Debye-Hückel type equation. The binding ability of the different polymers has been investigated towards Ca2+, Zn2+ and Sn2+ and, different speciation models have been obtained. For Acusol 445™, the weak interactions with Na+ and K+ have been determined. The effect on the complexing ability of a secondary inorganic ligand, the fluoride, has been evaluated on Carboxymethyl cellulose and Acusol systems; the formation of ternary mixed complexes with a significant increasing stability with respect the binary species has been obtained. The sequestering ability of the polymers towards the metal cations has been evaluated by means the empirical parameter pL 0.5. [ABSTRACT FROM AUTHOR]

Abstract Metal pollution, coming from both natural and anthropogenic sources, has become one of the most serious environmental problems. Various strategies have been tested with the aim of removing heavy metals from environment. In this contribution, containing a robust experimental work together with a critical literature analysis, the sequestering ability of a variety of ligands towards Sn2+ cation will be evaluated in the conditions of several natural fluids, i.e. sea water, fresh water, human blood plasma, urine and saliva. 13 structural and 11 thermodynamic descriptors will be selected for a total of thirty-eight molecules belonging to different classes (carboxylic acids, amines, amino acids, phosphonates, polyelectrolytes etc. …). For the filling of those missing data relative to the 11 thermodynamic descriptors, different strategies will be adopted, including simple correlations and Nipals algorithm. The evaluation of the sequestering ability of the ligands is assessed in terms of estimation of pL 0.5 (total concentration of ligand required to bind the 50% of metal in solution), an empirical parameter that takes into account all the side reactions in solutions and does not depend on the speciation scheme. Partial least square calculations were performed to model the pL 0.5 and to determine its correlation with the abovementioned descriptors. The possibility to design and build up new tailor-made molecules capable of effectively sequester Sn2+ in various conditions is crucial for practical applications in biosphere, hydrosphere and lithosphere. Graphical abstract Unlabelled Image Highlights • The data published for the interaction of Sn2+ with 38 molecules are surveyed. • A chemometric approach for the estimation of unknown thermodynamic data is given. • Amino groups and thiols are important for the efficient sequestration of Sn2+. • The work is useful for applications in biosphere, hydrosphere and lithosphere. • PLS coefficients help in design new ligands for the efficient sequestration of Sn2+. [ABSTRACT FROM AUTHOR]

Abstract A new polyaminocarboxylic bis-(3-hydroxy-4-pyridinone), derivative of DTPA, DTPA(PrHP) 2 , was synthesized starting from maltol by means of a coupling reaction of a protected 3-hydroxy-4-pyridinone and DTPA bis-anhydride. The DTPA(PrHP) 2 acid-base behavior was investigated by UV–Vis spectrophotometry and spectrofluorimetry at I = 0.15 mol L−1 in NaCl (aq) at T = 298.15 K and T = 310.15 K. To confirm the speciation scheme, also 1H NMR measurements were performed at T = 298.15 K. The protonation constants obtained from the cited different analytical techniques showed good accordance and were also in agreement with data reported in the literature. The complexing ability of DTPA(PrHP) 2 towards divalent (Ca2+, Cu2+, Zn2+) and trivalent (Al3+, Fe3+) cations was studied by potentiometric, UV–Vis spectrophotometric and 1H NMR titrations at T = 298.15 K and I = 0.15 mol L−1 in NaCl (aq). The fitting analysis of experimental data led to the determination of different speciation models consisting of M p L q H r (pn+r-5q) species with different stoichiometry and protonation stages, hydrolytic mixed and polynuclear complexes. The equilibrium model and complex formation constants, obtained from various analytical techniques, are in good agreement. The sequestering ability of the ligand towards the metal cations was assessed through the determination of the pL 0.5 and pM parameters at different pH values and pH = 7.4, respectively, which showed to follow the trend Fe3+ > Al3+ > Cu2+ > Ca2+ > Zn2+. Finally, biodistribution studies were carried out in mice previously injected with the radiotracer 67Ga–citrate to evaluate the in vivo ability of DTPA(PrHP) 2 as chelating agent towards trivalent metal cations. Graphical abstract Metal chelation capacity based on the pM values calculated vs. pH for different Mn+/bis-3-hydroxy-4-pyridinone (DTPA(PrHP) 2) systems; in vivo M3+ sequestration. Unlabelled Image Highlights • A new polyaminocarboxylic bis-(3-hydroxy-4-pyridinone), derived from diethylenetriaminepentaacetic acid, was synthesized. • Its acid-base behavior and complexation towards M2+ and M3+ were investigated. • The sequestering ability of the ligand towards Mn+ was studied using the pL 0.5 parameter determination at different pHs. • The pM values, calculated at physiological pH, follows the trend: Fe3+ > Al3+ > Cu2+ > Ca2+ > Zn2+. • Biodistribution studies indicated that the ligand has high in vivo chelating ability towards trivalent metal cations. [ABSTRACT FROM AUTHOR]

Abstract A new bis-(3-hydroxy-4-pyridinone) ligand (NTA(PrHP) 2), derived from nitrilotriacetic acid (NTA), was synthesized and evaluated for its selective solution metal complexation capacity as well as its in vivo sequestering power for hard metal cations. After the study of its acid-base properties and determination of the protonation constants, the binding ability of NTA(PrHP) 2 towards divalent (Ca2+, Cu2+, Zn2+) and trivalent (Al3+, Fe3+) metal cations was investigated by means of UV–Vis spectrophotometric, potentiometric and 1H NMR measurements. The determined speciation models consist of M p L q H r species with different stoichiometry. The obtained stability constants for the M L species follow the trend: Fe3+ > Al3+ > Cu2+ > Zn2+ > Ca2+. Furthermore, the sequestering ability of the ligand towards these metal cations was investigated by the determination of the pL 0.5 and pM parameters calculated at different pHs and pH = 7.4, respectively. High pL 0.5 values were obtained with significant variation of the sequestering ability with the investigated pH range. Analysis of the pM values at pH = 7.4 showed that the metal-ligand affinity follows the trend: Fe3+ > Al3+ > Cu2+ > Zn2+ > Ca2+. Finally, in vivo assays were performed to verify the efficacy of NTA(PrHP) 2 as sequestering agent towards trivalent metal cations, when administered to mice preloaded with the radiotracer 67Ga–citrate. Graphical abstract A new bis-(3-hydroxy-4-pyridinone) ligand, NTA(PrHP) 2 , with illustration of the its metal chelation capacity and selectivity based on the pM values calculated vs. pH for the different Mn+/ligand systems (a, Ca2+ = Image 4 , Cu2+ = Image 3 , Zn2+ = Image 2 , Al3+ = Image 1 , Fe3+ = ○) and its in vivo excretion capacity in animal model (mice overload with 67Ga) (b). Unlabelled Image Highlights • A new bis-(3-hydroxy-4-pyridinone) ligand derived from nitrilotriacetic acid was synthesized. • Its acid-base properties and binding ability towards M2+ and M3+ were investigated. • The sequestration of the ligand towards Mn+ was studied by the determination of pL 0.5 values at different pHs. • Analysis of pM values at pH = 7.4 showed that the metal-ligand affinity follows the trend Fe3+ > Al3+ > Cu2+ > Zn2+ > Ca2+. • Bioassays indicated that the ligand has high in vivo chelating ability towards trivalent metal cations. [ABSTRACT FROM AUTHOR]

This paper reports the results on the study of a set of synthesized bifunctional 3-hydroxy-4-pyridinones chelators as potential aluminium sequestering agents. They were N -functionalized with alkyl-amino, -carboxylic and –(amino-carboxylic) groups, envisaging the improvement of the Al 3+ sequestering capacity, in comparison with the marketed chelating drug deferiprone. The main focus of this work was given to the assessment of their binding ability towards Al 3+ , which was studied by potentiometric and UV–Vis spectrophotometric measurements carried out at T  = 298.15 K. The speciation models were characterized by Al p L q H r (3p+r−qz) species with different stoichiometry. Depending on ligand side-chain structures and on their thermodynamic properties, different trends of stability was found. Furthermore, the sequestering ability of the ligands towards Al 3+ was investigated by the calculation of pL 0.5 values at different experimental conditions. These results clearly indicate that the presence of amino-carboxylic groups in the ligands increases the sequestering ability towards Al 3+ . The in silico evaluation of pharmacokinetic descriptors indicated no violation to the Lipinski's rule and drug-likeness properties. Furthermore, the in vivo bioassays on a model of metal-overload mice showed for three investigated ligands a higher metal-sequestering capacity than for the chelating drug deferiprone, thus suggesting their potential interest as Al-chelating drug candidates. [ABSTRACT FROM AUTHOR]

• Thermodynamic studies on the Al3+/Dop- in NaCl (aq) , the main inorganic compound of biological fluids and natural waters. • Use of ISE-[H+] potentiometry, UV–Vis spectrophotometry, 1H NMR and thermogravimetry for the speciation studies. • Modelling of I /mol dm−3 and T /K by means of the modified extended Debye-Hückel, Specific Ion Interaction Theory. • Modelling of the sequestering ability at different I /mol dm−3, T /K and pH. The interactions of dopamine (Dop−) with aluminum were studied in NaCl (aq) at different ionic strengths (0.15 ≤ I /mol dm−3 ≤ 1.0) and temperatures (288.15 ≤ T /K ≤ 310.15). The investigations were carried out by using ISE-[H+] potentiometry, UV–Vis spectrophotometry and 1H NMR. The results obtained from the different techniques were in good agreement, both in terms of speciation model and stability constants of the complexes. The speciation model is featured by mononuclear complexes, namely: AlDop; AlDopOH; AlDop(OH) 2 and AlDop(OH) 3 (charges omitted). From 1H NMR investigations, it resulted that both the amino and the phenolic groups in meta position of aromatic ring are involved in the protonation equilibria, while the Al3+ complexation occurs from the catechol side of the ligand. The dependence on the ionic strength and temperature of the complex formation constants was modelled by a modified extended Debye-Hückel equation, containing a term for the dependence on T /K. The SIT approach allowed the calculation of the specific ion interaction coefficients of the aluminum:dopamine complexes. From the enthalpy change values obtained, it resulted that the formation of the species is exothermic in nature and that the entropy is the driving force of the processes. The sequestering ability of dopamine towards Al3+ was evaluated by the calculation of pL 0.5 parameter at different ionic strengths, pHs and temperatures; the dependence of the pL 0.5 on these variables was modelled by using an empirical predictive equation that allows the calculation of the effective sequestering ability of dopamine at desired conditions. The precipitates collected at the end of the potentiometric titrations were studied by means of thermogravimetric (TGA) analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • • Two novel water-soluble, proton-ionizable, isomeric tetraamino-dihydroxy-tetraoxacalix[4]arene were synthesized. • • Six protonation constants were determined, and the distribution diagrams for the seven protonated species were calculated. • • The phloroglucinol-derived oxacalix[4]arene 1 ·H 2 was successfully employed to complex paraquat both at low and high pH. • • Combination of protonation and apparent binding constants gave association constants for the differently-charged complexes. Tetraamino-dihydroxy-oxacalix[4]arenes 1 ·H 6 4+·4Cl– and 2 ·H 6 4+·4Cl– were synthesized in two steps from off-the-shelf components, and subjected to in-depth investigations on their molecular and supramolecular properties. UV–Vis titrations with aqueous NaOH provided six discrete protonation constants along with the distribution diagram for each of the oxacalixarenes, while a 1H NMR titration of 1 ·H 6 4+·4Cl– with NaOD (aq) , combined with DFT (B3LYP/6–311++G(d,p)) calculations allowed to shed light on the conformational preferences of macrocycle 1 ·H n (n–2)+ in the different protonation states. 1H NMR titrations with N , N ′-dimethyl-4,4′-bipyridinium (paraquat) dichloride gave, at different pH values, apparent association constants (K app) for the formation of the host–guest complexes. K app values, combined with the protonation constants, in turn provided the stability constant for the individual complexes between paraquat and 1 ·H n (n–2)+ in the different states of ionization, and allowed to identify 1 ·H– as the most efficient paraquat receptor. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO 2 ) impacts the greenhouse effect significantly and results in global warming, prompting urgent attention to climate change concerns. In response, CO 2 capture has emerged as a crucial process to capture carbon produced in industrial and power processes before its release into the atmosphere. The main aim of CO 2 capture is to mitigate the emissions of greenhouse gas and reduce the anthropogenic impact on climate change. Biopolymer nanocomposites offer a promising avenue for CO 2 capture due to their renewable nature. These composites consist of biopolymers derived from biological sources and nanofillers like nanoparticles and nanotubes, enhancing the properties of the composite. Various biopolymers like chitosan, cellulose, carrageenan, and others, possessing unique functional groups, can interact with CO 2 molecules. Nanofillers are incorporated to improve mechanical, thermal, and sorption properties, with materials such as graphene, carbon nanotubes, and metallic nanoparticles enhancing surface area and porosity. The CO 2 capture mechanism within biopolymer nanocomposites involves physical absorption, chemisorption, and physisorption, driven by functional groups like amino and hydroxyl groups in the biopolymer matrix. The integration of nanofillers further boosts CO 2 adsorption capacity by increasing surface area and porosity. Numerous advanced materials, including biopolymeric derivatives like cellulose, alginate, and chitosan, are developed for CO 2 capture technology, offering accessibility and cost-effectiveness. This semi-systematic literature review focuses on recent studies involving biopolymer-based materials for CO 2 capture, providing an overview of composite materials enriched with nanomaterials, specifically based on cellulose, alginate, chitosan, and carrageenan; the choice of these biopolymers is dictated by the lack of a literature perspective focused on a currently relevant topic such as these biorenewable resources in the framework of carbon capture. The production and efficacy of biopolymer-based adsorbents and membranes are examined, shedding light on potential trends in global CO 2 capture technology enhancement.

In this structure-activity relationship (SAR) study, we report the development of dual inhibitors with antiviral properties targeting the SARS-CoV-2 main protease (M pro ) and human cathepsin L (hCatL). The novel molecules differ in the aliphatic amino acids at the P2 site and the fluorine position on the phenyl ring at the P3 site. The identified dual inhibitors showed K i values within 1.61 and 10.72 μM against SARS-CoV-2 M pro ; meanwhile, K i values ranging from 0.004 to 0.701 μM toward hCatL were observed. A great interdependency between the nature of the side chain at the P2 site and the position of the fluorine atom was found. Three dual-targeting inhibitors exhibited antiviral activity in the low micromolar range with CC 50 values >100 μM. Docking simulations were executed to gain a deeper understanding of the SAR profile. The findings herein collected should be taken into consideration for the future development of dual SARS-CoV-2 M pro /hCatL inhibitors., Competing Interests: The authors declare no competing financial interest., (© 2024 American Chemical Society.)

Deferiprone, generally, is considered an important chelating agent for Fe 3+ overload. From a literature data analysis, a lack of information on the interaction of this molecule toward a series of metal cations emerged, inducing to fill out the topic. The complexing ability of deferiprone toward Ca 2+ , Mg 2+ , Cd 2+ and Pb 2+ was studied by potentiometry and 1 H NMR spectroscopy, in KCl aqueous solutions at different ionic strength values (0.1 ≤ I/mol dm -3 ≤ 1.0) and T = 298.15 K. The same speciation model featured by the ML, ML 2 , ML 3 and ML(OH) (M = metal and L = deferiprone or DFP) species was obtained for Cd 2+ and Pb 2+ ; the formation constants calculated at infinite dilution are: log T β = 7.23±0.02, 12.47±0.03, 16.70±0.04, and -2.53±0.04, respectively for Cd 2+ and 9.91±0.01, 15.99±0.02, 19.93±0.05 and 0.99±0.02 for Pb 2+ . Only two species, namely ML and ML 2 , were determined for Ca 2+ and Mg 2+ , whose formation constants at infinite dilution are respectively: 3.72±0.01 and 6.50±0.02, for the first one, 5.31±0.01 and 9.58±0.01, for the second. The ligand sequestering ability and affinity toward M 2+ were evaluated by determining the pL 0.5 and pM parameters at different pHs and ionic strengths. The results suggest that deferiprone has the best complexing and sequestering ability toward Pb 2 + , followed by Cd 2+ , Mg 2+ and Ca 2+ , respectively. 1 H NMR studies confirmed the DFP affinity for Cd 2+ and Pb 2+ , and in combination with DFT calculations showed that metal cations are bound to the hydroxo-oxo moiety of the pyridinone ring. The data reported in this study provide information on the possible employment of a small molecule like deferiprone, as a chelating and sequestering agent for Pb 2+ accumulation or overload from environmental and biological matrices., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)