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Pillar[n]arenes are a relatively new family of macrocyclic molecular hosts, consisting of methylene-linked phenol-based monomers attached in a para-substituted configuration. The macrocyclic nature of these molecules provides a well-defined internal cavity, into which smaller guest molecules can be included to form supramolecular host-guest inclusion complexes. The para-oriented attachment yields relatively rigid cylindrical or pillar-like molecular and cavity shapes, hence the name. In addition to the unique shape of these cavities (compared to the related meta-substituted calixarenes, for example), the aromatic nature of the cavity walls also contributes to distinctive host properties of pillar[n]arenes and guest affinities. Neutral pillar[n]arenes, such as those with alkyl substituents, are generally insoluble in water, and thus their host properties are studied in nonaqueous media. This review article will provide a comprehensive summary of the reported host binding studies of pillar[n]arenes in nonaqueous solution. A wide range of specific pillar[n]arenes have been studied in this way, as have a wide variety of sizes and types of guests. The emphasis will be on studies in which the value of the binding association constant Ka was measured and reported, to consider the effect of guest size, shape, and nature and the host size and substituents on the binding ability of pillar[n]arenes. The main objective of the paper is to provide a summary and overview of the host binding abilities of this fascinating family of molecular hosts in nonaqueous solution. [ABSTRACT FROM AUTHOR]

Characterizing complicated solution phase systems in situ requires advanced modeling techniques to capture the intricate balances between the many chemical species. Due to the error inherent in any scientific measurement, a spectrophotometric titration experiment with nickel(II) and ethylenediamine (en) was repeated six times using an autotitrator to test the replicability of the data and the consistency of the resulting thermodynamic model. All six datasets could be modeled very tightly (R2 > 99.9999%) with the following eight complexes: [Ni]2+, [Ni2en]4+, [Nien]2+, [Ni2en3]4+, [Nien2]2+, [Ni2en5]4+, [Nien3]2+, and [Nien6]2+. The logK values for the stepwise associative reactions agree with existing literature values for the majority species ([Nienn = 1–3]2+) and matched expectations for the minority species; 95% confidence intervals for each logK value were determined via bootstrapping, which quantifies the variability in the binding constant value that is supported by a given dataset. The repeated experiments, which could not be successfully concatenated together, demonstrate that replication is crucial to capturing all the variability in the logK values. Conversely, bootstrapped confidence intervals across multiple experiments can be readily combined to generate an appropriate range for an experimentally determined binding constant. [ABSTRACT FROM AUTHOR]

The interactions of clofazimime (CLF) with human serum albumin (HSA), bovine serum albumin (BSA) and calf thymus DNA (ct-DNA) were studied by square-wave voltammetry (SWV) at physiological pH. The cyclic voltammogram of CLF gave three reversible redox peak couples in the studied medium. SWV data showed that the cathodic current of CLF decreased by adding of HSA, BSA and ct-DNA owing to the molecular binding interactions. For these binding processes, thermodynamic quantities (ΔG°, ΔH° and ΔS°) and binding constants (K) were obtained and calculated from voltammetry data in the temperature range 295–310 K. Also, the molecular docking studies were carried out to obtain theoretical information about the interactions of CLF with A-DNA, B-DNA and serum albumins. The results of docking applications showed that CLF had the highest binding affinity (BA) for BSA. [ABSTRACT FROM AUTHOR]

Drug‐surfactant interaction increases the solubility of poorly water‐soluble drugs and design better pharmaceutical formulations. The degree of interaction of nepafenac (NP), a nonsteroidal anti‐inflammatory prodrug was studied with ionic surfactant molecules such as cationic surfactant cetrytrimethyl ammonium bromide (CTAB) and anionic surfactant sodium dodecyl sulphate (SDS) in an aqueous medium at room temperature. NP made mixed micelles with CTAB and SDS. To investigate the influence of interactions, conductivity measurements, UV–visible spectroscopy, and fluorescence measurements were recorded. The quantification of NP–surfactant interactions was investigated using various mathematical models. The CMC values determined from conductivity measurements of pure surfactants were 0.96 mM for CTAB and 8.14 mM for SDS near to their literature values. At different mole fractions of NP in UV measurements, binding constants from lnKb were found 0.025 and 0.123 and number of NP molecules per micelles (n) 67, 46 for CTAB and SDS, respectively. The mixed micelles of NP–CTAB and NP–SDS revealed that CTAB has a strong interaction with NP than SDS. The Benesi–Hildebrand relationship, Stern–Volmer and Kawamura replica for the partition coefficient were used to confirm the findings. We are confident that the host–guest interaction mechanism can contribute to a better understanding of molecular recognition in the phospholipid membrane model. [ABSTRACT FROM AUTHOR]

Research background. Fish by-products are discarded as waste, which has a significant impact on the environment. They have no economic value, but there are many opportunities to turn them into high value products. Due to significant quantities generated internationally and the continuous expansion of the market for ω-3 and ω-6 fatty acids as nutraceuticals, innovative technological approaches are needed to transform this waste into marketable products with added value, while limiting the risk of environmental pollution. Experimental approach. In this study, two temperatures (40 and 60 °C) at a constant pressure during the extraction of anchovy by-products with supercritical CO2 fluid were used to determine extraction yield, fatty acid, tocopherol and phytosterol composition, followed by microencapsulation with two matrices based on the transglutaminase-mediated crosslinking reaction between whey protein isolates and casein. Before microencapsulation, the binding parameters were estimated using quenching studies. Results and conclusions. The results showed a higher content of total fatty acids when extracted at 40 °C, resulting in two fractions on a dry mass basis of (712±12) mg/g in the fraction obtained in the separator with code S40 and (732±10) mg/g in the fraction obtained in the separator with code S45, respectively. The monounsaturated (MUFAs) and polyunsaturated fatty acids (PUFAs) accounted for 40-44 %. The extracts showed a higher mass fraction of eicosapentaenoic acid ((28.7±1.0) mg/g) in fraction S45 when extracted at 60 °C. A minimum inhibitory and bactericidal concentration of 0.66 μg/mL against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 was found for all fractions. Higher binding constants were found for palmitoleic and oleic acids than for palmitic acid. The control variant, without crosslinking, enabled the microencapsulation of a higher amount of fatty acids, while in both powders the sum of MUFAs and PUFAs was 40 %. Novelty and scientific contribution. The approaches used in our study open up new opportunities for adding value to the fish by-products through extraction and microencapsulation, extending their potential use to food, cosmetics and nutraceuticals. [ABSTRACT FROM AUTHOR]

One of the major concerns worldwide is the rapid increase in water pollution with hazardous heavy metals. The Cucurbit[n]uril (CB[n]) structure provides an inner hydrophobic cavity accessible through two electrostatically negative portals with polar carbonyl groups, allowing for charged ion–dipole interaction between cationic species with excellent binding affinities. In this work we selected CB[5], and CB[7] for the titrimetric and electrochemical evaluation of the heavy metal complexes formed with Copper(II), Cadmium(II) and Lead(II). The host–guest interaction was found by either attenuation of the redox peaks, the formation of a new peak, or the slight shift in the redox peaks of the heavy metal ions. Titration data were obtained for CB[n] with the heavy metal solutions to determine the molar coefficient of binding. The stoichiometry of the complexes was 1 : 1 by Job′s plot. We calculated the binding constants using the Benesi–Hildebrand method achieving relatively good binding constants (K) ranging from (1.80±0.14)×105–(4.98±0.13)×105 M−1. The results showed that the complexes of Cadmium(II) and Lead(II) with both CB[5] and CB[7] are highly stable in aqueous media. Copper(II) was able to bind to the smaller sized portal of CB[5], whereas with CB[7] the heavy metal ion could not form a favourable complex. This phenomenon suggests that the CB[5] is an ideal host at forming stable host–guest interactions than their larger homologue. [ABSTRACT FROM AUTHOR]

Research background. Fish by-products are discarded as waste, which has a significant impact on the environment. They have no economic value, but there are many opportunities to turn them into high value products. Due to significant quantities generated internationally and the continuous expansion of the market for ω-3 and ω-6 fatty acids as nutraceuticals, innovative technological approaches are needed to transform this waste into marketable products with added value, while limiting the risk of environmental pollution. Experimental approach. In this study, two temperatures (40 and 60 °C) at a constant pressure during the extraction of anchovy by-products with supercritical CO2 fluid were used to determine extraction yield, fatty acid, tocopherol and phytosterol composition, followed by microencapsulation with two matrices based on the transglutaminase-mediated crosslinking reaction between whey protein isolates and casein. Before microencapsulation, the binding parameters were estimated using quenching studies. Results and conclusions. The results showed a higher content of total fatty acids when extracted at 40 °C, resulting in two fractions on a dry mass basis of (712±12) mg/g in the fraction obtained in the separator with code S40 and (732±10) mg/g in the fraction obtained in the separator with code S45, respectively. The monounsaturated (MUFAs) and polyunsaturated fatty acids (PUFAs) accounted for 40–44 %. The extracts showed a higher mass fraction of eicosapentaenoic acid ((28.7±1.0) mg/g) in fraction S45 when extracted at 60 °C. A minimum inhibitory and bactericidal concentration of 0.66 μg/mL against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 was found for all fractions. Higher binding constants were found for palmitoleic and oleic acids than for palmitic acid. The control variant, without crosslinking, enabled the microencapsulation of a higher amount of fatty acids, while in both powders the sum of MUFAs and PUFAs was 40 %. Novelty and scientific contribution. The approaches used in our study open up new opportunities for adding value to the fish by-products through extraction and microencapsulation, extending their potential use to food, cosmetics and nutraceuticals.

The dynamic behaviour of a chemical system made of two coupled reactions is compared with that of a mechanical system consisting of two oscillating bodies connected by springs. First, the principle of energy departure from equilibrium is employed to derive the motion equations of both systems. Subsequently, the relevant characteristic frequencies and the amplitude parameters are obtained and analysed in terms of "Normal Modes". The results show that systems belonging to different branches of science can be analysed using the same methodologies. To elucidate the application of Normal Modes to chemistry, the dynamic analysis of a system consisting of a proton transfer reaction coupled to a complex formation reaction is described in the Supporting Information: the procedure enables the evaluation of rate constants, equilibrium constants and reaction enthalpies of a reacting chemical system made of two coupled reactions. The method is then extended to a cycle of three reactions. [ABSTRACT FROM AUTHOR]

Binding constants (K) are foundational to supramolecular chemistry and quantified by modelling spectroscopic (NMR, UV-vis) titration data according to chemical equilibria. Spurred by growth in data science, the tools and methods for determining K values have accelerated in recent years. To share these advances, we provided a Workshop on Quantifying Binding Constants at ISMSC 2023 in Iceland and herein share the objectives, processes, and recommendations. We framed this short course in terms of learning to drive, from the basics 'under the hood', to 'behind the wheel', and navigating 'the open road'. These steps are crucial in the 'drive to K-town', where participants appreciate the importance of building, analysing, and comparing models. K-town is where they assess the hazards of incomplete models, inaccurate K values, and incorrect uncertainty assessment. We conclude with the Supramolecular Chemist's Pledge as a starting point for considering quality control in determining K values. [ABSTRACT FROM AUTHOR]

The cationic antimicrobial ß-hairpin, thanatin, was recently developed into drug-like analogues active against carbapenem-resistant Enterobacteriaceae (CRE). The analogues represent new antibiotics with a novel mode of action targeting LptA in the periplasm and disrupting LPS transport. The compounds lose antimicrobial efficacy when the sequence identity to E. coli LptA falls below 70%. We wanted to test the thanatin analogues against LptA of a phylogenetic distant organism and investigate the molecular determinants of inactivity. Acinetobacter baumannii (A. baumannii) is a critical Gram-negative pathogen that has gained increasing attention for its multi-drug resistance and hospital burden. A. baumannii LptA shares 28% sequence identity with E. coli LptA and displays an intrinsic resistance to thanatin and thanatin analogues (MIC values > 32 µg/mL) through a mechanism not yet described. We investigated the inactivity further and discovered that these CRE-optimized derivatives can bind to LptA of A. baumannii in vitro, despite the high MIC values. Herein, we present a high-resolution structure of A. baumannii LptAm in complex with a thanatin derivative 7 and binding affinities of selected thanatin derivatives. Together, these data offer structural insights into why thanatin derivatives are inactive against A. baumannii LptA, despite binding events in vitro. [ABSTRACT FROM AUTHOR]

The stability of cationic functional groups is one of the key factors determining lifetime of alkaline anion‐exchange membranes (AAEMs) and the AAEM‐based electrochemical devices. Main‐group metal and crown ether complexes are stable cations due to the absence of degradation pathways including nucleophilic substitution, Hofmann elimination, and cation redox. However, the binding strength, a key feature for AAEM applications, is overlooked in previous work. We herein propose the use of barium [2.2.2]cryptate ([Cryp‐Ba]2+) as a new cationic functional group for AAEMs due to its extremely strong binding (109.5 M−1 in water at 25 °C). The [Cryp‐Ba]2+‐AAEMs with polyolefin backbones remain stable after treatment in 15 M KOH at 60 °C for over 1500 hours. More importantly, these AAEMs are successfully applied in water electrolyzers, and an anolyte‐feeding switch method is designed to further reveal the influence of binding constants. [ABSTRACT FROM AUTHOR]

In this work, according to the data obtained from the induced circular dichroism spectra, the studied porphyrin binds to DNA by the intercalation method, and its Zn-containing analog by the externally ordered interaction was revealed. The absorption spectra of the studied complexes were obtained at different DNA concentrations, and the binding parameters (Kb, n) of porphyrins with DNA were computed from the data at two values of the ionic strength of the solution. It is shown that the places for binding porphyrins become less accessible at a higher ionic strength of the solution. An increase in the melting temperature of DNA in the presence of a metal-containing porphyrin is also observed, as well as a decrease in the stabilizing effect of porphyrins for an increase in the ionic strength of the solution. [ABSTRACT FROM AUTHOR]

There are a number of uncertainties regarding plasma protein binding and blood distribution of the active drugs favipiravir (FAVI), molnupiravir (MOLNU) and imatinib (IMA), which were recently proposed as therapeutics for the treatment of COVID-19 disease. Therefore, proton dissociation processes, solubility, lipophilicity, and serum protein binding of these three substances were investigated in detail. The drugs display various degrees of lipophilicity at gastric (pH 2.0) and blood pH (pH 7.4). The determined pKa values explain well the changes in lipophilic character of the respective compounds. The serum protein binding was studied by membrane ultrafiltration, frontal analysis capillary electrophoresis, steady-state fluorometry, and fluorescence anisotropy techniques. The studies revealed that the ester bond in MOLNU is hydrolyzed by protein constituents of blood serum. Molnupiravir and its hydrolyzed form do not bind considerably to blood proteins. Likewise, FAVI does not bind to human serum albumin (HSA) and α1-acid glycoprotein (AGP) and shows relatively weak binding to the protein fraction of whole blood serum. Imatinib binds to AGP with high affinity (logK′ = 5.8–6.0), while its binding to HSA is much weaker (logK′ ≤ 4.0). The computed constants were used to model the distribution of IMA in blood plasma under physiological and 'acute-phase' conditions as well. [ABSTRACT FROM AUTHOR]

The inhibitory effects on mushrooms tyrosinase activity of some semi- and thiosemicarbazones were investigated. While the semicarbazones are inactive, the thiosemicarbazones are, in general, more active than the reference (kojic acid, IC50 = 70 μM), with maximum activity obtained with benzaldehyde thiosemicarbazone (IC50 = 7 μM). These inhibitors probably act by coordination of the copper(II) metal ions in the active site of tyrosinase: effectively, potentiometric studies conducted in water solutions confirm that the most active thiosemicarbazone is a good ligand for copper(II) ions. The tyrosinase CD spectra do not show any significant difference by addition of an inhibitor or an inactive compound. On the contrary, interesting results were obtained by spectrofluorimetric titrations of mushrooms tyrosinase aqueous solutions with some of the investigated compounds, giving helpful information about possible mechanism of action. The thiosemicarbazones here reported are not cytotoxic on human fibroblasts and do not activate cells in a pro-inflammatory way. [ABSTRACT FROM AUTHOR]

A proposed validated square‐wave voltammetric method and high‐performance liquid chromatography, as a comparative method, are applied to measure simultaneously two metabolites‐ of current use pesticides‐ namely 3,5,6‐trichloro‐2‐pyridinol and malathion dicarboxylic acid. Method validation and quality control parameters are studied. Method detection limits are found to be 0.043 and 0.061 μg/ml for 3,5,6‐trichloro‐2‐pyridinol and malathion dicarboxylic acid, respectively whereas the practical quantification limits are found to be 0.135 and 0.193 μg/ml (voltammetry), 0.05 and 0.1 μg/ml (high‐performance liquid chromatography) for 3,5,6‐trichloro‐2‐pyridinol and malathion dicarboxylic acid, respectively. The application of the proposed method for the analysis of water samples collected from different sources has been assessed. The interaction of these metabolites with human serum albumin was studied, a 1:1 association complex was formed and their binding constants were evaluated through the calculation to be 0.30 × 102/M for 3,5,6‐trichloro‐2‐pyridinol and 8.414 × 103/M for malathion dicarboxylic acid. The low value of the binding of 3,5,6‐trichloro‐2‐pyridinol metabolite indicates that this metabolite is more likely to be more toxic than the other metabolite. [ABSTRACT FROM AUTHOR]

The quantitative description of the supramolecular interaction occurring at the adhesion surfaces of different polymers has enabled elaborate dissections of contributions to cohesive and surface energies. An alternative analysis is proposed here based on solubility parameters and binding constants that traditionally describe the weakest and relatively larger association energies in polymer blends. The article emphasizes a feature of supramolecular polymers that has not received adequate consideration: The dynamic bond scrambling that allows a most efficient molecular recognition over significant areas of synthetic and biological surfaces.

The formation of supramolecular complexes of 3-methyl-sulfido-propoxycalix[4]arene-methylene-bis-phosphonic acid with seventeen amino acids in aqueous solutions has been studied and their stability coefficients have been determined by the method of high-performance liquid chromatography. The structures of the supramolecular complexes have been proposed by molecular modeling and the influence of structural factors (the stabilization of different conformations of the obtained complexes depending on amino acid nature: possibilities of the realization of hydrogen bonds and electrostatic interactions between different groups of the amino acids and calixarene) on the stability of the supramolecules has been shown. [ABSTRACT FROM AUTHOR]

Periphyton contains extracellular polymeric substances (EPS), yet little is known about how periphyton EPS affect the speciation and mobility of mercury (Hg(II)) in aquatic systems. This study extracted and characterized EPS from periphyton in Florida Everglades, and explored its role in Hg(II) binding and speciation using multiple approaches. Results from Fourier transform infrared spectroscopy (FTIR) revealed that colloidal and capsular EPS were primarily comprised of proteins, polysaccharides, phospholipids, and nucleic acids. Ultrafiltration experiments demonstrated that 77 ± 7.7% and 65 ± 5.5% of Hg(II) in EPS solution could be transformed into colloidal and capsular EPS-bound forms. Three-dimensional excitation emission fluorescence spectra (3D-EEMs) showed that the binding constants (Kb) between colloidal/capsular EPS and Hg(II) were 3.47×103 and 2.62×103 L·mol−1. Together with 3D-EEMs and FTIR, it was found that the protein-like and polysaccharide-like substances in EPS contributed to Hg(II) binding. For colloidal EPS, COO- was the most preferred Hg(II) binding group, while C-N, C-O-C, and C-OH were the most preferred ones in capsular EPS. Using the stannous-reducible Hg approach, it was found that EPS significantly decreased the reactive Hg(II). Overall, this study demonstrated that EPS from periphyton are important organic ligands for Hg(II) complexation, which may further affect the migration and reactivity of Hg(II) in aquatic environment. These observations could improve our understanding of Hg(II) methylation and accumulation within periphyton in aquatic systems. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is a neurodegenerative disease accompanied by progressive cognitive and memory dysfunction due to disruption of normal electrotonic properties of neurons and neuronal loss. The Na,K-ATPase interaction with beta amyloid (Aβ) plays an important role in AD pathogenesis. It has been shown that Na,K-ATPase activity in the AD brain was significantly lower than those in age-matched control brain. The interaction of Aβ42 with Na,K-ATPase and subsequent oligomerization leads to inhibition of the enzyme activity. In this study interaction interfaces between three common Aβ42 isoforms, and different conformations of human Na,K-ATPase (α1β1) have been obtained using molecular modeling, including docking and molecular dynamics (MD). Interaction sites of Na,K-ATPase with Aβ42 are localized between extracellular parts of α- and β- subunits and are practically identical for Na,K-ATPase at different conformations. Thermodynamic parameters for the formation of Na,K-ATPase:Aβ42 complex at different conformations acquired by isothermal titration calorimetry (ITC) are similar, which is in line with the data of molecular modeling. Similarity of Na,K-ATPase interaction interfaces with Aβ in all conformations allowed us to cross-screen potential inhibitors for this interaction and find pharmaceutical compounds that could block it. [ABSTRACT FROM AUTHOR]

Computation of binding constants from spectrophotometric titration data is a very popular application of chemometric hard modeling. However, the calculated values are misleading if the correct binding model is not used. Given that many supramolecular systems of interest feature unknown speciation, a priori determination of binding stoichiometry constitutes an important unsolved problem in chemometrics. We present a new and reliable algorithm for accomplishing this task, implemented using a hybrid particle swarm optimization technique. Simultaneous optimization of stoichiometry ratios and binding constants allows the optimal binding model to be calculated in just a few minutes for systems with up to four reactions. Simulated data studies demonstrate that the algorithm finds the correct stoichiometry with up to nine reactions in the absence of noise, including accurately determining species with unusual stoichiometry, such as H2G5. Application to four experimental datasets shows the algorithm is robust to experimental errors for a variety of chemical systems and binding models. This algorithm will facilitate the discovery of complex binding models, increase efficiency in titration analysis, and avert incorrect stoichiometry models, thereby improving the reliability of binding constant information in spectrophotometric titrations. A new and reliable algorithm for computing binding constants from spectrophotometric titration data is presented. A hybrid particle swarm technique simultaneously optimizes the stoichiometry ratios and binding constants in minutes for experimental datasets with up to four reactions. Simulated data studies demonstrate that the algorithm finds the correct stoichiometry with up to nine reactions in the absence of noise. This algorithm will facilitate the discovery of complex binding models, increase efficiency in titration analysis, and avert incorrect stoichiometry models. [ABSTRACT FROM AUTHOR]

Protein adsorption studies returned to the focus of medical therapeutics, when it was found that up to 2500 non-plasma proteins adsorbed to hip implants during arthroplastic surgery, challenging peri-implant healing models. Questions have re-emerged as to the implications of uncontrolled protein unfolding after adsorption. In past studies on the cooperativity of protein binding we discovered protein adsorption hysteresis, a thermodynamically irreversible process. The present precursory study comprises real-time kinetic (TIRF-Rheometry) and equilibrium (125I-tracer ) studies on the hysteretic binding of fibrinogen and rhBMP-2 to titanium and glass surfaces via transient states. Thermodynamic constants (GOn), as well as kinetically derived (K'A ) and hysteresis derived (K'HA ) association constants in the range of 106 to 1012 M-1lead to a consistent picture.

Plant-derived bioactive substances have demonstrated significant qualities that suggest they may be crucial in preventing various chronic diseases. Flavonoids, which include apigenin, are the biggest group of polyphenols. In our study, we aimed to obtain the methanol-chloroform (1:1) extract from the aerial parts of Nepeta baytopii Hedge & Lamond and purify the apigenin using bioactivity-guided isolation to separate the active fraction. The current in vitro study provides updated knowledge on apigenin regarding its previously unresearched DNA protection activity and enzyme inhibition, enzyme inhibition kinetics, and enzyme-apigenin interactions. In this context, these studies will be the first and will contribute to the literature. Apigenin had high urease (IC 50 -5.00 ± 0.00 µM), butyrlcholinesterase (BChE:IC 50 -10.48 ± 0.00 µM), and tyrosinase (IC 50 -177.82 ± 14.40 µM) inhibition activities, while inhibition binding constants were high in urease (K i -0.05 mM), tyrosinase (K i -0.06 mM), and carbonic anhydrase (K i -0.08 mM). The binding affinities and constants of the interaction were also ascertained to be high for BChE (-9.50 kcal/mol, and K i -0.11 µM), and tyrosinase (-8.80 kcal/mol, and K i , 0.62 µM) with apigenin. In summary, apigenin can be used as an inhibitor for five enzymes. These results will give priority to further studies. Apigenin showed high DNA protection activity with a Form I value of 67.37%. These data demonstrated that the interaction formed by BChE-apigenin gave the best results regarding enzyme inhibition and enzyme-molecule interaction. The stability of this complex was evaluated using molecular dynamics modeling.

[Display omitted] • Albumin binds sulfonephthaleins provoking colour transitions, called metachromasy. • The joint effect of pH, I and dye pK a on Dye-Albumin binding is still unclear. • The interaction of BSA with five dyes is screened in different conditions (pH, I). • Principal Component Analysis allows to rationalise dyes' spectral changes. • Binding conditional constants are determined for the most relevant system. Albumin is undoubtedly the most studied protein thanks to its widespread diffusion and biochemistry; despite its binding ability towards different dyes, provoking dye's colour change, has been exploited for decades for quantification purposes, the joint effect of working pH, ionic strength, and dye's p K a still remains only sporadically discussed. In the present study, the interaction of Bovine Serum Albumin (BSA) with five dyes belonging to the sulfonephthalein group, Bromophenol Blue (BPB, p K a = 3.75), Bromocresol Green (BCG, p K a = 4.42), Chlorophenol Red (CPR, p K a = 5.74), Bromocresol Purple (BCP, p K a = 6.05) and Bromothymol Blue (BTB, p K a = 6.72), is investigated at four working pH values (3.5, 6.0, 7.5 and 9.0) and two ionic strength conditions by UV–Vis spectroscopy. Principal Component Analysis is then applied to rationalize dye behavior upon BSA addition at each pH value and to summarize the protein effect on dyes' spectral features, identifying three general behaviors. The most relevant systems are then submitted to further characterization involving a solution equilibria study aimed at determining conditional binding constants for the selected DSA-dye adducts and fluorescence, CD, and 1H NMR spectroscopy to evaluate the binding effect on the species involved. [ABSTRACT FROM AUTHOR]

Pillar[n]arenes are a relatively new class of macrocyclic host molecules which have not been extensively studied for their ability to form inclusion complexes. The properties and host–guest inclusion complexes of dimethoxypillar[5]arene (DMPill[5]) hosts with the polarity-sensitive fluorescent probes 8-anilinonaphthalene-1-sulfonic acid (1,8-ANS) and 2-anilinonaphthalene-6-sulfonic acid (2,6-ANS) as guests were investigated in nonaqueous solvents via fluorescence spectroscopy. The binding properties of DMPill[5] were found to depend significantly on the shape of the guest molecule, as well as on the properties of the solvent. Formation of host–guest inclusion complexes of DMPill[5] with these two fluorescent ANS guests occurred in the polar aprotic solvents acetonitrile, acetone, and tetrahydrofuran. Fluorescence titration experiments were performed to determine the nature and strength of the complexation. In the case of 1,8-ANS, 1:1 host–guest complexation was observed in all three solvents, with average binding constant K values of 408, 1000 and 5500 M−1 in acetone, acetonitrile, and tetrahydrofuran, respectively. This large dependence of the binding constant on solvent provides insight into the nature of the binding in these complexes. In the case of 2,6-ANS, 2:1 host–guest complexation was observed; this difference with 1,8-ANS was explained in terms of the shape and size of these two isomeric guests. These results show that DMPill[5] is an excellent host for these neutral aromatic guests, and shows strong binding abilities even in these nonaqueous solvents. The strength (or lack) of binding in different solvents was found to be dependent on a range of factors beyond solvent polarity, including guest and solvent shape and size, and most importantly, specific solvent–solute interactions. [ABSTRACT FROM AUTHOR]

The involvement of non-canonical DNA structures, such as Gquadruplex (G4) DNA, in cancer development and progression has set the pace towards the renaissance of DNA-binding metal complexes. In this work, we report the DNA-binding of three Ni(II), Cu(II), Zn(II) complexes of a salphen-like N4-donor ligand, bearing two imidazole groups condensed with a phenylenediamine moiety. Both duplex and G4 DNAs derived from human telomeres (hTelo), and a sequence mimicking the promoter of the oncogene myc (c-myc) were studied. UV-Vis and circular dichroism spectroscopic binding studies pointed out that, while all the three complexes bind the selected oligonucleotides, the Cu(II) derivative is the strongest and G4-selective compound of the series. Lastly, FRET DNA melting assay results on the Cu(II) complex/hTelo G4 system were interpreted by a loop-binding mechanism of interaction, as corroborated by molecular dynamics (MD) simulations. [ABSTRACT FROM AUTHOR]

Micellar enhanced ultra-filtration (MEUF) is a modified ultrafiltration (UF) method that can remove small molecules that are not effectively removed by UF alone. In this work we used a similar semi-equilibrium dialysis (SED) method to characterize two anionic surfactants, sodium dodecyl sulfate (SDS) and sodium laurate (SOL), as MEUF candidates to remove several polycyclic aromatic hydrocarbon (PAH) compounds. These anionic surfactants have low toxicity and are more biodegradable compared to the fairly toxic and persistent cetyltrimethylammonium bromide (CTABr) and similar cationic surfactants, which is important as MEUF surfactants may be present in the treated effluent. The log binding constants (Log KB) of the PAHs naphthalene, phenanthrene, pyrene and fluorene to SDS ranged from 3.07 to 4.48, which compared well with the previous results for CTABr and indicated that SDS is an excellent candidate for MEUF. The log binding constants for the same PAHs with SOL micelles ranged from 2.11 to 3.53, which suggested that SOL might be adequate for stronger-binding PAH like pyrene and fluorene but less suitable for naphthalene and phenanthrene. The results demonstrated a strong correlation between the Log KB with one micelle type and the Log KB with the other, suggesting a common set of properties and interactions are responsible for the binding. Similar to the previous results for CTABr, a significant correlation between Log KB and Log KOW values indicates that hydrophobic character is the main driving force for PAH binding with these anionic micelles. This may also be useful for predicting MEUF performance for various compound/surfactant combinations where Log KB is not known.

In this article, capillary electrophoresis was applied to investigate the chiral recognition mechanism for the enantioseparation on a well‐known second‐generation photodynamic therapy drug of benzoporphyrin derivative monoacid ring A, that is, verteporfin. In our previous study, cholate salts have been studied as the chiral selectors, which can realize baseline separation of the four verteporfin isomers. Aiming to reveal the chiral recognition mechanism, the separation effect of several kinds of chiral selectors was discussed. According to the results and references, the chiral separation mechanism of this system was concluded: the analytes selectively combine with the chiral micelles, that is, dynamic H‐bonds interactions occur between the hydroxyl groups on the outer side of the cholate micelles and the ester/carboxy groups of the four isomers. In addition, the role of dimethyl formamide as an organic modifier was also researched, including reducing the effective mobility of the analytes and mobility of electroosmotic flow, and preventing them from adsorbing to the capillary wall and self‐aggregating of verteporfin, which are pretty beneficial for separation. The method used in this article provides a direct and reliable solution to study the mechanism of chiral separation. [ABSTRACT FROM AUTHOR]

Lanthanide complexes are of increasing importance in cancer diagnosis and therapy. In the present study 1:1 and 1:3 solid complexes of La (III)–5‐FU (5‐fluorouracil) were prepared and characterized. In solution, the formation of 1:1 La (III) and Eu (III) complexes enabled the enhancement of 5‐FU's effectiveness. Binding constants of the 1:1 complexes of both metals were estimated using spectrophotometry and HPLC with fluorescence detection methods. The thermodynamic parameters ΔG°, ΔH°and ΔS°were calculated using differential scanning calorimetry. Evaluation of the cytotoxic activity of the 1:1 La (III)‐ and Eu (III)–5‐FU complexes was performed through two methodologies, trypan blue for cell viability where La (III)‐ and Eu (III)–5‐FU complexes were found to have 52,000 and 80,000 dead cells, respectively, and via flow cytometric analysis to measure the apoptotic values, which were found to be 59.87 and 86.86% respectively. [ABSTRACT FROM AUTHOR]

Oxovanadium(IV) complexes [VO(HL1)2] and [VO(H2L2)2] from 2-aminobenzoic acid (HL1) and 2-hydroxybenzoic acid (HL2) were synthesized and characterized by 1HNMR, 13CNMR, mass (ESI–MS), X-ray diffraction (XRD), conductivity measurements, FTIR spectral data, and melting points. Based on the above analytical data, the complexes have the general formula [VO(HL)2]. The interaction of the complexes with donor compounds (biological relevance) was performed and investigated with absorption spectroscopy. 1:1 Adduct compounds of oxovanadium complexes as an acceptor with adenine, cytosine, and guanine as an electron donor were studied by FTIR technique and viscosity measurements. FTIR technique was used to determine the binding constants for adduct compounds. [ABSTRACT FROM AUTHOR]

The current investigation explores the association and complexation of the mixture of anionic surfactant, sodium dodecyl sulfate (SDS), and antibiotic drug, ofloxacin (OFC) as well as nonionic surfactant, Triton X-100 (TRX) and OFC drug respectively in several additive solutions. The investigations were performed by applying conductivity and UV-Visible spectroscopic techniques. The impacts of drug concentration, types of solvents, and composition of aq. solutions of alcohols (methanol (MeOH), ethanol (EtOH), and 1-propanol (1-PrOH)) as well as temperature change have been investigated on the micelle formation of SDS + OFC mixture. The micellization of SDS + OFC and TRX + OFC systems has been characterized by the determination of critical micelle concentration (CMC) from conductivity vs. SDS concentration (conductivity technique) and Absorbance vs log[TRX] (UV-Visible spectroscopic technique) plots respectively. The micellization of SDS was delayed owing to the introduction of the OFC drug while the effect has been intensified as a function of OFC concentration. At a fixed OFC concentration and temperature, the CMC values were acquired to be augmented with the upsurge of alcohol concentration. The enhancement of the CMC changes has been perceived with the escalation of temperature at a definite concentration of OFC in water and 5% (w/w) aq. alcohols media. The disfavor of micellization of TRX in aq. EtOH solutions in comparison to aqueous solution also detected from UV-Visible spectroscopic technique. The binding constant (K b) for the complexation of TRX with OFC drug was determined using the Benesi-Hildebrand plot. The K b values were obtained to be affected by the change of solvent and temperature. The negative free energy change (∆ G m o / ∆ G b o) of the micellization and complexation demonstrate the spontaneous occurrence of micelle formation and complex development. The enthalpy changes (∆ H m o) of micellization were negative (exothermic process) and entropy changes (∆ S m o) were positive (highly disordered and entropy-dominated micellization). Other thermodynamic properties (( ∆ H b o and ∆ S b o) and thermodynamics of transfer) have been evaluated and illustrated as well, for the working systems. [Display omitted] [ABSTRACT FROM AUTHOR]

A crystallographic investigation of a series of host–guest complexes in which small‐molecule organic guests occupy the central cavity of an approximately cubic M8L12 coordination cage has revealed some unexpected behaviour. Whilst some guests form 1:1 H⋅G complexes as we have seen before, an extensive family of bicyclic guests—including some substituted coumarins and various saturated analogues—form 1:2 H⋅G2 complexes in the solid state, despite the fact that solution titrations are consistent with 1:1 complex formation, and the combined volume of the pair of guests significantly exceeds the Rebek 55±9 % packing for optimal guest binding, with packing coefficients of up to 87 %. Re‐examination of solution titration data for guest binding in two cases showed that, although conventional fluorescence titrations are consistent with 1:1 binding model, alternative forms of analysis—Job plot and an NMR titration—at higher concentrations do provide evidence for 1:2 H⋅G2 complex formation. The observation of guests binding in pairs in some cases opens new possibilities for altered reactivity of bound guests, and also highlights the recently articulated difficulties associated with determining stoichiometry of supramolecular complexes in solution. [ABSTRACT FROM AUTHOR]

Human serum albumin (HSA) is the binding cargo in blood plasma. The binding of drugs to HSA determines the pharmacokinetics and pharmacodynamics of the drugs. There are 67 natural genetic variants of HSA were reported in literature. Studying the effect of albumin modifications on drug binding helps to treat the patients with proper medication. In the present study, we have aimed to understand the effect of two natural variants of HSA, such as Herborn (K240E) and Milano Slow (D375H) on the binding of phenylbutazone and ibuprofen. For this, we have generated K240E and D375H mutants and also double mutant (K240E/D375H) of HSA using site directed mutagenesis. The recombinant HSA and its variants were expressed in Pichia pastoris. The interaction of HSA and its variants to phenylbutazone and ibuprofen was studied using fluorescence spectroscopy. Our results showed that there is no significant effect of K240E and D375H mutations on phenylbutazone and ibuprofen binding. But the effect is significant when both the mutations were there in a single protein (K240E/D375H). Further, the CD spectroscopy data showed that there is no effect of phenylbutazone and ibuprofen binding on the conformation of protein, except in case of D375H, where there is a conformational change in the binding pocket with the ibuprofen binding. • The HSA variants Herborn (K240E), Milano Slow (D375H) and the double mutant (K240E/D375H) were expressed using P. pastoris. • Variants are having reduced α-helical content. • There is no significant effect of K240E and D375H mutations on phenylbutazone and ibuprofen binding. • Double mutant (K240E/D375H) showed reduced binding to phenylbutazone and ibuprofen. • There is no effect of phenylbutazone and ibuprofen binding on the conformation of the proteins. [ABSTRACT FROM AUTHOR]

A new and highly efficient colorimetric Cu2+ chemosensor HL, synthesized by condensation between 8-hydroxyjulolidine-9-carboxaldehyde and 1,8-diaminonaphthalene, has been rationally designed and thoroughly studied. In a buffered aqueous methanol mixture, interactions between HL and Cu2+ produce an intense visible band at 421 nm, considerably red-shifted (~ 100 nm) from the peak maxima of HL (320 nm). Absorbance spectrophotometry experiments pointed to an exceptional 2.3 nM limit of detection (LoD) calculated from the ratiometric response upon Cu2+ binding. Furthermore, without the aid of instrumentation an impressive 0.5 µM LoD is possible by naked-eye observations, far below the 31.5 µM (2 mg/L) guidelines for drinking water established by the World Health Organization. Spectrophotometric pH titrations allowed the determination of the equilibrium constants and speciation plots for the formation of the various chemical species of HL in the absence and presence of Cu2+, with only mononuclear complexes being found. Additional studies highlighted the selectivity of HL to Cu2+ when in the presence of other metal ions, and a 1:1 (M:L) binding stoichiometry has also been confirmed with results from Cu2+ titrations, Job's plot and ESI-HRMS in good agreement. The Cu2+ sensing mechanism was also found to be reversible by cycling with H2Na2EDTA. [ABSTRACT FROM AUTHOR]

The interaction between (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD) and water-soluble betulin derivatives, betulin 3,28-disulfate (DSB) and betulin 3-acetate-28-sulfate (ASB), belonging to the class of pentacyclic lupane triterpenoids, was studied using affinity capillary electrophoresis. It was found that 1:1 and 1:2 complexes were formed. The stability constants of the complexes in the temperature range of 293.15–318.15 K were determined. The values obtained are sufficiently large; log K (1:1) and log K (1:2) are 4.25–5.02 and 6.08–7.59, respectively. This phenomenon can be explained by the presence of broad hydrophobic regions in the molecules of the compound studied. The stability constants decrease with increasing temperature. The stability constants for ASB complexes are slightly higher as compared to the constants for DSB complexes. The thermodynamic parameters for the complexation were calculated from the van't Hoff plots. The complexation was found to be controlled by the enthalpy change. The obtained values of stability constants at 298 K were compared with values for the β-CD complexes of the compounds under study and for the HP-β-CD and β-CD complexes of water-insoluble betulin derivatives. It was found that water-soluble betulin derivatives form more stable complexes with CDs as compared to water-insoluble derivatives (betulonic and betulinic acids), and the HP-β-CD complexes are more stable than the β-CD complexes. • Betulin 3,28-disulfate and betulin 3-acetate-28-sulfate form 1:1 and 1:2 complexes with (2-hydroxypropyl)-β-cyclodextrin • Logarithms of stability constants are >4 • The complexation is controlled by the enthalpy change • Water-soluble betulin derivatives form more stable complexes with CDs as compared to water-insoluble derivatives • The HP-β-CD complexes are more stable than the β-CD complexes [ABSTRACT FROM AUTHOR]

• New 8-oxadiazole spiropyrans undergo positive photochromism. • 8-oxadiazole spiropyrans form complexes with transition metal ions. • Complexes of merocyanines with Zn2+, Cd2+ possess negative photochromism. • Cation induced isomerization into merocyanine complexe can be controlled by light. • Photochromic transformations can be driven by transition metal ions. New 8-(5-(p -tolyl)-1,3,4-oxadiazol-2-yl) substituted spirobenzopyrans appear as polychromogenic molecular system demonstrating both positive photochromism and ionochromic properties. Introduction of electron withdrawing formyl group into 6-position of the pyran part leads to increasing of spiropyran photocoloration reaction efficiency but decreases thermodynamical stability of merocyanine form complexes. Upon irradiation with visible light colored solutions of complexes with Zn2+, Cd2+ ions exhibiting negative photochromism, undergo reversible discoloration as a result of photodissociation characterized by the quantum yields reaching 46%. On one side this allows realizing controlled by light irradiation cation induced isomerizations into complexes of the merocyanine form. On the other hand, a system, in which direction of photochromic transformations can be driven by transition metal ions, can be designed. [ABSTRACT FROM AUTHOR]

Metallobacitracins are complexes with an extensive antimicrobial and biological activity. In this work, we investigated the metal complexation of bacitracin with several divalent metal ions in aqueous solution. The binding constants of Zn(2+), Cd(2+), Hg(2+), Cu(2+), Ni(2+), Pd(2+), Fe(2+), Mn(2+) and Mg(2+) to bacitracin were measured by UV/Vis spectroscopy, isotermic titration calorimetry (ITC) and potentiometry while the complexes were studied by Circular Dichroism and Nuclear Magnetic Resonance (15N HSQC) for Zn(2+), Cd(2+) and Hg(2+) at different pH. By UV/Vis spectroscopy the affinity is in the range 104 to 105 M−1 at pH 6 and follows the order Ni(2+) > Cd(2+) > Hg(2+) > Zn(2+) > Fe(2+). By potentiometry, the binding constants were determined in the pH range 2–12. Microcalorimetry shows that the stoichiometry of metallobacitracins investigated is 1:1 with binding constants in the range 105–102 M−1 at pH 6 and with an order of stability of Ni(2+) > Cd(2+) > Zn(2+) > Hg(2+); ΔS, ΔH and ΔG parameters were also determined. NMR spectroscopy lets us establish the binding site of the metal ion when comparing 15N HSQC of free bacitracin and complex in natural abundance; these findings agree with calorimetric results. Chemical shift changes in complexes containing Zn(2+) and Cd(2+) exhibit a similar behavior despite pH differences. Conversely, there is not a significant change for Hg(2+) complex. The obtained data contribute to understand the mechanism of the biological activity of the metallobacitracins and give the guideline for the design of more powerful metalloantibiotics. Unlabelled Image • Binding constants of an extended set of divalent ions to bacitracin are reported • Diverse metallobacitracins are studied by different experimental methodologies • The studies are carry out in aqueous solution in a non-competitive buffer • There is evidence of the amino acids involved in the formation of metallobacitracins [ABSTRACT FROM AUTHOR]

Abstract Micellar enhanced ultrafiltration (MEUF) has been shown to be an effective removal technique for a variety of trace contaminants in wastewater, especially for water soluble low molecular weight organic contaminants. In MEUF, contaminants first partition into surfactant micelles prior to removal by ultrafiltration, where the contaminants are below the molecular weight cut-off of the ultrafiltration membrane but the micelles are above the cut-off. Binding constants of selected Polycyclic aromatic hydrocarbons (PAHs) such as naphthalene, phenanthrene, pyrene and fluorene have been determined in order to examine the removal efficiency of MEUF for PAHs with Cetyltrimethylammonium bromide (CTABr) using a semi equilibrium dialysis method. PAHs show strong binding with CTABr because of hydrophobic interactions. Our results enabled us to develop a relationship between binding constant (log K B) and log K OW for neutral compounds, which will be useful for predicting MEUF performance for PAHs removal from waste water. The range of our reported binding constant values are from 2.61 to 5.07. Highlights • Semi-equilibrium dialysis (SED) was used to determine Micelle binding constants. • Neutral PAH binds with CTABr micelles by hydrophobic interaction. • Log K B values determined through SED demonstrate a positive correlation with Log K OW. • Fluorene exhibited the higher tendency to bind with CTABr micelles. [ABSTRACT FROM AUTHOR]

Abstract CaCO 3 precipitation is one of the most common and important geochemical processes in the arid inland waters and it can be significantly affected by interaction of DOM with Ca2+. Effects of the drastic seasonal change of water salinity on interaction of DOM with Ca2+ in the arid inland waters were completely unknown. In the present study, complexation of DOM with Ca2+ in the freshwater (0.5‰ salinity) and hypersaline water (70‰ salinity) were comparatively examined by excitation-emission matrix (EEM) fluorescence quenching titration and isothermal titration calorimetry (ITC). The complexation of DOM with Ca2+ was significantly influenced by the drastic change of salinity. The ITC complexation is exothermic at 0.5‰ salinity but turns to an endothermic process at 70‰ salinity. More energy is needed for the complex reaction between DOM and Ca2+ under the hypersaline condition than in the fresh water. Fluorescence quenching titration indicates that DOM has stronger binding ability toward Ca2+ in the freshwater than in the saline water, and more fractions of DOM in the freshwater are accessible to Ca2+ than in the saline water. Ca2+ complexation in the DOM is dominated by the tryptophan-like components at both salinities and the complexation of Ca2+ with fulvic acid-like components is ignorable. The findings is important for understanding the aquatic geochemical processes in some lakes that seriously affected by irrigation water use in the arid zone. Graphical abstract Seasonal change of salinity significantly affects Ca2+ complexation of dissolved organic matter. Unlabelled Image Highlights • DOM-Ca2+ complexation under freshwater and hypersaline water was investigated. • DOM-Ca2+ complexation was exothermic at 0.5‰ salinity and endothermic at 70‰ salinity. • More energy is needed for the complexation between DOM and Ca2+ under the hypersaline condition. • DOM had stronger binding ability toward Ca2+ in the freshwater than in the hypersaline water. • The tryptophan-like substances were the dominant components in DOM for Ca2+ complexation. [ABSTRACT FROM AUTHOR]

Interaction of moxifloxacin hydrochloride (MFH) with tetradecyltrimethylammonium bromide (TTAB) along with Triton X-100 (TX-100) under different experimental conditions has been carried out using multiple physico-chemical techniques. The micellar parameters like critical micelle concentration (cmc), counter ion binding (β), thermodynamic parameters such as , , and etc. associated with the drug-TTAB interaction have been determined. The changes of the values of cmc of TTAB by the addition of drug indicate the existence of TTAB-MFH interaction. The cmc values of drug-TTAB systems were found to be dependent on the variation of temperature, salt and alcohol concentrations. In all the cases the negative values of indicated the spontaneous micelle formation of drug-TTAB system. The values of and reveal the existence of hydrophobic and electrostatic interactions between drug and TTAB. The CP values of TX-100 in water were increased in the presence of MFH. The values of of drug-TX-100 mixed system are found to be positive which indicates the clouding process is nonspontaneous in nature. The binding constant (Kb) value for MFH-TX-100 system was found to be temperature dependent and the binding interaction between MFH and TX-100 is mainly due to hydrogen bonding. [ABSTRACT FROM AUTHOR]

The present study embodies the detail of interaction of Complex 1,Bis(N-phenyl-o-methoxybenzohydroxamato)Molybdenum(VI): [N-PMBHA-Mo(VI)] and Complex 2,Bis(N-phenylbenzohydroxamato)Tungsten(VI): [N-PBHA-W(VI)] with ct-DNA (Calf thymus-DNA) and its consequences by UV–Visible absorption spectroscopy, fluorescence spectroscopy, three-dimensional fluorescence spectroscopy, viscosity measurements and molecular docking. The intrinsic binding constant, Kb of complexes were determined which follows the order as complex 1 > complex 2 along with variation in shift and intensity for the complexes. Fluorescence spectroscopy applied for the determination of Stern–Volmer quenching constant, binding constant and the number of binding sites which reveals groove mode of binding. Non-radiative energy transfer between donor and acceptor molecule exposed by Förster energy transference theory (FRET) studies. The increase in the relative viscosity of ct-DNA with increasing the concentration of the complex 1 and complex 2 is also revealed. FTIR analysis also revealed that both the complexes interacted positively with bases and phosphates of ct-DNA. The docking studies complemented the experimental results revealing minor groove mode of binding for both the complexes. Finally, the in-vitro cytotoxicity studies indicate that the complexes have excellent anticancer activity against the breast cancer cell line, MCF-7, which could be a constructive guideline to produce new generations of anticancer agents. [ABSTRACT FROM AUTHOR]

[Display omitted] • QSPR models are developed for binding constants of cyclodextrin complexes. • Molecular size and shape parameters are considered specifically for modeling. • Experiments and predictions of binding constants for ionic liquids are performed. A generic method for predicting the complexation performance of cyclodextrins complexes is desirable. Two quantitative structure–property relationship models are established for the complexation performance of α- and β-cyclodextrins. The datasets consist of 229 α-cyclodextrin and 330 β-cyclodextrin complexes, including conventional organic molecules, ionic organic compounds, and drugs. Internal validation, indicated by the squared correlation coefficient (Q 2) of 0.8949 and 0.8954 for α- and β-cyclodextrin models, demonstrates the stability and robustness of these models. For external validation, the squared correlation coefficients of test sets (R 2 test) are 0.9315 (α-cyclodextrin model) and 0.9171 (β-cyclodextrin model), confirming the predictive ability of both models. Furthermore, the complexation performances of two ionic liquids are measured using UV spectrometric titration for our models' external prediction. The mean absolute error between measured and calculated values for β-cyclodextrin complexes is 0.20 M−1, indicating the satisfactory transferability of the model. For the α-cyclodextrin model, the mean absolute error of 1.25 M−1 is deemed acceptable. Both the model validations and experimental results underscore the robustness and predictive performance of these models. In conclusion, these developed models could effectively predict binding constants of several types of molecules with cyclodextrins, which can become valuable tools for cyclodextrin design. [ABSTRACT FROM AUTHOR]

• Micellization of STS and SDS in presence of GCL are examined. • STS with longer hydrophobic chain solubilizes GCL better than SDS. • RSA% of GCL + STS > GCL + SDS. • STS is a better choice for GCL than SDS. Gliclazide (GCL) is used widely for reducing hyperglycemia in diabetic patients. It has poor solubility which leads to low oral bioavailability because of significant first-pass metabolism. In this work, we have employed two anionic micellar solutions of different hydrophobic chain lengths to solubilize GCL. They are sodiumtetradecyl sulfate (STS) and sodiumdodecyl sulfate (SDS). Our results reveal that longer hydrophobic chain was better suited for solubilizing GCL. The drug-surfactant interactions were assessed through FT-IR, conductivity, UV-Spectrophotometry, dynamic light scattering and antioxidant study. The results were compared with computational studies. There was negative free energy of micellization and positive entropy of micellization GCL + STS and GCL + SDS systems predicting spontaneity of the processes as calculated from the conductivity experiments. From the UV spectral studies, using Benesi-Hildebrand (B-H) equation, the binding constants demonstrated higher value for GCL + STS (0.286 M−1) compared to GCL + SDS (0.0231 M−1). The antioxidant properties of the above two combinations show that STS (93.14 %) has higher radical scavenging activity (RSA %) compared to SDS (77.45 %). Protein binding studies too indicated higher binding constant for STS than SDS with the drug. The docking model also supported the above findings. The longer hydrophobic chain length facilitated the solubilization of GCL with improved properties. This study offers a novel drug formulation for widely used drug GCL. [ABSTRACT FROM AUTHOR]

In aqueous media, VIV- and VV-ions and compounds undergo chemical changes such as hydrolysis, ligand exchange and redox reactions that depend on pH and concentration of the vanadium species, and on the nature of the several components present. In particular, the behaviour of vanadium compounds in biological fluids depends on their environment and on concentration of the many potential ligands present. However, when reporting the biological action of a particular complex, often the possibility of chemical changes occurring has been neglected, and the modifications of the complex added are not taken into account. In this work, we highlight that as soon as most vanadium(IV) and vanadium(V) compounds are dissolved in a biological media, they undergo several types of chemical transformations, and these changes are particularly extensive at the low concentrations normally used in biological experiments. We also emphasize that in case of a biochemical interaction or effect, to determine binding constants or the active species and/or propose mechanisms of action, it is essential to evaluate its speciation in the media where it is acting. This is because the vanadium complex no longer exists in its initial form.

The interaction between cationic chlorophyll photosensitizers (PSs) for antimicrobial photodynamic therapy and non-ionic surfactant Tween 80 as a potential carrier system was studied using absorption and fluorescence spectroscopy. The results, analyzed in terms of our approach and the Stern–Volmer approach, indicate that all three PSs form stable molecular complexes with Tween 80, the PS molecules being located at the periphery of surfactant micelles next to hydrophilic head groups. The higher the charge of the macrocyclic cation, the stronger the interaction of PS with the surfactant. [ABSTRACT FROM AUTHOR]

Understanding the interactions between amines and the surface of gold nanoparticles is important because of their role in the stabilization of the nanosystems, in the formation of the protein corona, and in the preparation of semisynthetic nanozymes. By using fluorescence spectroscopy, electrochemistry, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and molecular simulation, a detailed picture of these interactions is obtained. Herein, it is shown that amines interact with surface Au(0) atoms of the nanoparticles with their lone electron pair with a strength linearly correlating with their basicity corrected for steric hindrance. The kinetics of binding depends on the position of the gold atoms (flat surfaces or edges) while the mode of binding involves a single Au(0) with nitrogen sitting on top of it. A small fraction of surface Au(I) atoms, still present, is reduced by the amines yielding a much stronger Au(0)-RN. + (RN . , after the loss of a proton) interaction. In this case, the mode of binding involves two Au(0) atoms with a bridging nitrogen placed between them. Stable Au nanoparticles, as those required for robust semisynthetic nanozymes preparation, are better obtained when the protein is involved (at least in part) in the reduction of the gold ions., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

The aim of the present study was to develop a spectrophotometric based assay for the determination of binding parameters like binding constant and binding free energy of the free and 1,1-diphenyl-2-picrylhydrazyl (DPPH) bound forms of a set of antioxidant standards (AS). The determination of binding constant and binding free energy is based upon the decrease in absorbance of the electronic absorption spectrum of a 10-4 M acetonitrile solution of DPPH in the presence of a given concentration of a solution of antioxidant standards in the same solvent.