Binding Constant Values Research Articles

A highly sensitive colorimetric and fluorogenic detection of copper(II) ion based on new picolylamine-armed calix[4]arene

In this study, two- and tetra-functionalized with bis(2-picolyl)amine calix[4]arene derivatives (2-PACX and 4-PACX) were synthesized, and their structures were confirmed by 1H NMR, 13C NMR, FT-IR and TOF-MS spectroscopies. Cation sensing behaviors of them were investigated towards several cations such as Fe2+, Al3+, Cr3+, Hg2+, Mn2+, Cu2+, Co2+, Cd2+, Zn2+, Ni2+, Ag+, Mg2+, Ca2+, Li+, Na+, and K+. The results showed that 4-PACX was an effective colorimetric sensor against Cu2+ ions. The binding constant (K) value of the complexation between 4-PACX and Cu2+ ion was calculated as 4.62x108 M−2 and the detection limit value of the sensor as 5.1 μM. Moreover, the fluorescence studies demonstrated that 4-PACX has great fluorogenic sensor potential with 0.16 μM of detection limit. As a result, good yield, large coupling constant with Cu2+ ion (Ka = 13.972), applicability to aqueous samples, low detection limit, and high sensitivity were some of the advantages of the obtained sensor.

Synthesis theoretical and experimental spectroscopic characterization of isoniazid-benzoic acid drug complexes: Insilico and invitro biological evaluations

New organic charge-transfer molecules were synthesised by salt formation from isoniazid and benzoic acid/aspirin compounds acting as acceptor and donor molecules. The synthesised charge transfer complexes were characterized and structurally confirmed by various instrumental techniques such as UV–visible, FT-IR, powder XRD, and NMR spectroscopic methods. Initially, compounds are studied molecular docking analysis with different kinds of proteins, such as 1HNY.pdb, 1PGG.pdb and 4-COX.pdb. Docking results have been compared with molecular electrostatic potential mapping and Mulliken charge distribution methods. Results show that both complexes IAC and IBC have almost the same binding constant value with 1HNY.pdb. Besides, IBC has a more binding constant than the IAC with inflammatory proteins (1PGG.pdb and 4-COX.pdb). The reactivity of the complexes is explained by the chemical potential and electrophilic index derived by the frontier molecular orbitals using the DFT method. These results show a more electrophilic index of IBC than the IAC indicating, more electron affinity nature of IBC. This is also reflected in the in-vitro biological studies, which shows IAC having better activity in anti-diabetic studies whereas IBC has better activity in anti-inflammatory studies. For the sake of complex ability, all biological and molecular docking experimental results are compared with standard drug molecules.

Supramolecular association of a diguanidine derivative with a porphyrin-cyclodextrin conjugate and its binding to G-Quadruplex DNA

G-quadruplex-selective small molecule binders are synthesized as they find relevance in therapeutic intervention. This article reports a new and novel diguanidine derivative containing benzimidazole moiety. The synthesized compound is characterized using spectroscopic techniques. An inclusion complex of the compound with a porphyrin-tethered β-cyclodextrin where the latter acts as a host molecule. The structure of the complex is optimized by employing a rotating-frame Overhauser effect spectroscopy. Two host molecules encapsulate the diguanidine forming a 1:2 complex, as evidenced by the spectral analysis. The compound and its inclusion complex are analyzed for their binding to duplex and G-quadruplex DNAs viz., kit22, myc22, and telo. The binding constants are derived using fluorescence spectroscopic titrations. The diguanide derivative: porphyrin-cyclodextrin complex shows stronger binding to the quadruplexes than the duplex DNA, with the binding constant values of (8.20 ± 0.51) × 105, (2.40 ± 0.28) × 106, and (8.20 ± 0.10) × 105 M−1 for the interaction with kit22, myc22, and telo, respectively. The complexed form of diguanidine shows a greater affinity for myc22 than the other G-quadruplexes and duplex DNA. Circular dichroism spectra are recorded to further analyze conformational alterations on the binding interaction. The binding characteristics of the ligands against various DNAs are discussed in detail.

Structural elucidation of new ferrocene appended scaffold and their metal complexes: Comparative in vitro DNA/BSA binding and antibacterial assay

A new organometallic ligand (L) was designed and synthesized from ferrocenecarboxaldehyde and 2–Aminobenzophenone through the condensation reaction in one step process. The metal complexes of this L with the formula [Zn(L)2](NO3)2 (1), [Cu(L)2](NO3)2 (2) and [Co(L)2](NO3)2 (3) were synthesized in high yield. The ligand (L) and complexes 1–3 were completely characterized by elemental analysis, spectroscopic and spectrometric techniques such as FT–IR, ToF Mass,1H NMR,13C NMR molar conductance and magnetic moment measurements. The spectroscopic interpretation showed that complex 1 and complex 3 prefer tetrahedral geometry whereas complex 2 adopts a square planar arrangement around the copper(II) ion. The in vitro DNA interaction studies of ligand (L) and metal complexes 1–3, were performed by UV–Vis absorption, fluorescence spectral and ethidium bromide displacement experiments. The absorption studies of complexes 1–3 reveal the existence of both hyperchromic and hypochromic effect which indicated the mixed type of binding that is intercalation of the aromatic part and the electrostatic surface interaction of metal ions with DNA phosphate groups. A comparison of binding constant Kb values suggested the stronger binding of complex 2 (Kb = 6.17 × 104 M−1) as compared to L and complexes 1 and 3. Furthermore, in vitro BSA binding studies and FRET also suggests greater interaction of complex 2 with BSA causing modulations in the hydrophobic microenvironment near Trp-212 in the subdomain IIA pocket by static quenching mechanism. Interestingly, all three complexes 1–3 tested showed promising antimicrobial activity as revealed by the disc diffusion assay in all four human pathogenic bacterial species comprising both gram–positive and gram–negative bacteria.

A study of azopyrimidine photoswitches and their interactions with cyclodextrins: When the guest governs the type of accommodation at the host

Azopyrimidines have recently emerged as a new class of photoswitches structurally similar to azobenzenes switching between trans and cis isomers. These compounds have a wide range of potential applications in photopharmacology, catalysis or as molecular devices, but their low solubility in water limits their biological applications. Nevertheless, this drawback could be overcome by their inclusion into supramolecular structures. To test this hypothesis, we prepared a series of azopyrimidines and investigated their structure, cis-trans isomerization and host-guest chemistry with cyclodextrins (CDs) using an experimental-theoretical approach combining capillary electrophoresis (CE), Nuclear Magnetic Resonance (NMR) spectroscopy and computational models. The results revealed that β-CD exhibits high selectivity over several CDs tested for the accommodation of the studied compounds. Orientation of guests in inclusion complexes was experimentally assessed by Nuclear Overhauser Effect (NOE) contacts and supported by quantum-chemical calculations. Moreover, investigation of noncovalent interactions of azopyrimidines with β-CD by CE showed that azopyrimidines with suitable structural modification can form strong complexes with high values of binding constants (over 17 000 L mol−1). For such complexes, trans-cis isomerization proceeds directly inside the β-CD cavity with azopyrimidine remaining encapsulated through its narrower primary portal. By contrast, in weakly interacting complexes, the trans isomer is released, and the cis isomer is generated outside the cavity. In subsequent re-complexation, the cis isomer is then re-captured through the wider secondary portal. Therefore, our findings point to two significantly different complexation processes depending on substitutional pattern and binding constant values of azopyrimidines; a feature which may lead to future promising applications.

Thioether-based novel transition metal complexes: Synthesis, DNA interaction, in vitro biological assay, DFT calculations, and molecular docking studies

A novel Schiff base ligand 2-(((2-(benzylthio)phenyl)imino)methyl)-4-chlorophenol and its cobalt, nickel, copper, and zinc metal complexes were prepared. Using B3LYP/6–31++G(d,p) method with LanL2DZ as basis set, the molecular structure of metal complexes has been optimized, and their parameters have been explored. The distorted octahedral geometries have been observed in cobalt, nickel, and copper complexes. In contrast, zinc complex exhibited distorted tetrahedral geometry indicating the coordination of metal ions with ligands through ONS binding sites, which are confirmed by various spectroscopic techniques, magnetic measurements, molar conductivity, elemental analysis, and DFT studies. The intercalative binding mode between CT-DNA and synthesized metal complexes has been determined by absorption and fluorescence spectroscopy. The binding constant values of metal complexes found to be varied from 5.28 × 103 M−1 to 9.18 × 104 M−1. Furthermore, several methods have been used to scrutinize the bioactivities, such as in vitro anti-diabetic, anti-inflammatory, and antioxidant. From the obtained results, it can be concluded that zinc metal complex exhibited excellent anti-inflammatory and anti-diabetic activity compared to others. However, the copper complex has good antioxidant property. Besides deducing the prospective binding energies of inhibitors, molecular docking simulations have also been conducted utilizing the enzyme structures of B-DNA, 6-COX, α-amylase, and α-glucosidase.

Solvent-regulated fluorescence off-on signaling of Ni(II) and Zn(II) with the formation of two mononuclear complexes with an ATP detection ability by Zn(II) assembly.

The current study shows that Schiff base HL, (Z)-2,4-dibromo-6-(((piperidin-2-ylmethyl)imino)methyl)phenol, can be used successfully as a selective chemosensor for Zn(II) and Ni(II) among several competing cations in purely aqueous and semi-aqueous media. Under UV light in methanol-water (9 : 1) HEPES buffer, the receptor gives its response by changing its color to cyan color in the presence of Zn(II) and to bluish cyan color in the presence of Ni(II). Surprisingly, the chemosensor can only reliably identify Zn(II) in a hundred percent aqueous medium by changing its color to light yellow. UV and fluorescence studies in both aqueous and semi-aqueous media are used to further investigate this Zn(II) and Ni(II) recognition phenomenon. The high values of the host-guest binding constants, obtained by electronic and fluorescence titration, ensure that a strong bond exists between HL and Ni(II)/Zn(II). As anticipated, two highly luminescent mononuclear, crystalline compounds, complexes 1 and 2, have been developed by a separate reaction of HL and Zn(II)/Ni(II), and the high luminous properties are due to the occurrence of Chelation Enhanced Fluorescence (CHEF). According to the single crystal structure, the asymmetric units of both complexes consist of two deprotonated chemosensor units and one Zn(II)/Ni(II), leading to the formation of an octahedral complex. For Ni(II) and Zn(II) sensing, the predicted LOD is in the nanomolar range. Both complexes 1 and 2 are fluorescence active and studies to check their ATP detection ability, but intriguingly, only complex 2 is capable of detecting ATP in a fully aqueous solution. Finally, the live cell imaging study validates the two sensors' biosensing functionality.

AlphaFold accelerates artificial intelligence powered drug discovery: efficient discovery of a novel CDK20 small molecule inhibitor.

The application of artificial intelligence (AI) has been considered a revolutionary change in drug discovery and development. In 2020, the AlphaFold computer program predicted protein structures for the whole human genome, which has been considered a remarkable breakthrough in both AI applications and structural biology. Despite the varying confidence levels, these predicted structures could still significantly contribute to structure-based drug design of novel targets, especially the ones with no or limited structural information. In this work, we successfully applied AlphaFold to our end-to-end AI-powered drug discovery engines, including a biocomputational platform PandaOmics and a generative chemistry platform Chemistry42. A novel hit molecule against a novel target without an experimental structure was identified, starting from target selection towards hit identification, in a cost- and time-efficient manner. PandaOmics provided the protein of interest for the treatment of hepatocellular carcinoma (HCC) and Chemistry42 generated the molecules based on the structure predicted by AlphaFold, and the selected molecules were synthesized and tested in biological assays. Through this approach, we identified a small molecule hit compound for cyclin-dependent kinase 20 (CDK20) with a binding constant Kd value of 9.2 ± 0.5 μM (n = 3) within 30 days from target selection and after only synthesizing 7 compounds. Based on the available data, a second round of AI-powered compound generation was conducted and through this, a more potent hit molecule, ISM042-2-048, was discovered with an average Kd value of 566.7 ± 256.2 nM (n = 3). Compound ISM042-2-048 also showed good CDK20 inhibitory activity with an IC50 value of 33.4 ± 22.6 nM (n = 3). In addition, ISM042-2-048 demonstrated selective anti-proliferation activity in an HCC cell line with CDK20 overexpression, Huh7, with an IC50 of 208.7 ± 3.3 nM, compared to a counter screen cell line HEK293 (IC50 = 1706.7 ± 670.0 nM). This work is the first demonstration of applying AlphaFold to the hit identification process in drug discovery.

Facile synthesis and anion binding studies of fluorescein/benzo-12-crown-4 ether based bis-dipyrromethane (DPM) receptors.

Two novel fluorescein as well as benzo-12-crown-4 ether functionalized dipyrromethane receptors (DPM3 and DPM4) have successfully been synthesized. The anion (used as their TBA salts) binding studies of thus prepared DPM3 and DPM4 receptors were evaluated by the UV-visible spectrophotometric titrations. Binding affinities as well as the stoichiometry were determined through the UV-visible titrations data with the involvement of the BindFit (v0.5) package available online at https://supramolecular.org. Moreover, binding events were validated by means of the comparison of the partial 1H-NMR spectrum of the simple host molecule with that of the host-guest complex, and the 1 : 1 stoichiometry were further confirmed by the Job's method of continuous variation. From the results, we observed the binding constant (Ka) values of DPM3/DPM4 with various tested anions in the range of 516.07 M-1 to 63789.81 M-1, depending upon the nature/shape/size of the anions. Moreover, the anion-π interactions were confirmed by the partial 1H-NMR spectral data, and further supported by the literature reported systems. The authors hope that such types of valued receptors will be benefitted in future for the recognizing/binding of a variety of biologically important anions.

Charge transfer interaction between 2, 3-Diamino-5-bromopyridine and 2, 4-Dinitrophenol: Synthesis, spectroscopic characterization, DNA binding analysis, and density functional studies

The e-donor 2, 3-Diamino-5-bromopyridine (5BPY) and the e-acceptor 2, 4-Dinitrophenol (DNP) were both involved in the synthesis of a new charge transfer complex, which was then characterized experimentally as well as theoretically. Several spectroscopic techniques were used to analyze the produced solid compound. 1H NMR, FT-IR, P-XRD and SEM-EDX analyses all confirmed the presence of charge and proton transfers in the resulting complex. Analysis of the complex DNA binding ability was carried out using electron absorption spectroscopy; the CT complex binding mechanism was determined to be intercalative, and the intrinsic binding constant (Kb) value was determined to be 7.2 × 106 M−1. To corroborate the results of the experiments, theoretical calculations were performed using DFT with a basis set of CAM-B3LYP/6-31 G (d, p). In accordance with the experimental findings, we calculated and analyzed the molecular electrostatic potential maps (MEPs), geometrical parameters and Mullikan atomic charges. The presence of an H-bond also affects the stability of the complex, in addition to e-transfer. The experimental findings are in agreement with the DFT calculations.

An AIE active fluorescence sensor for measuring Fe3+ in aqueous media and an iron deficiency anemia drug.

In this study, a new tetraphenylethene derivative bearing triazole and pyridine moieties (TPE-TAP) was synthesized using click chemistry. The fluorescence sensing properties of TPE-TAP were investigated in almost 100% aqueous media. For this purpose, first of all, structural characterization of the newly synthesized compound TPE-TAP was performed by NMR and HRMS analyses. Then, the optical behavior of TPE-TAP was investigated in different ratios of a THF-water mixture (0-98%). The obtained results showed that the best fluorescence for TPE-TAP was observed in the presence of 98% water in the medium. Then, the ion selectivity of TPE-TAP was determined using 19 different cations in the THF-water medium (2 : 98 v/v%). It was observed that among the cations studied, only Fe3+ quenched the fluorescence of TPE-TAP. The detection limit and binding constant values of TPE-TAP for Fe3+ were calculated as 1.3 μM and 26.65 M-2, respectively, from the graph results of the decrease in the fluorescence intensity of TPE-TAP in the presence of Fe3+ at different concentrations. In addition, the study investigating the selectivity of TPE-TAP in the presence of 18 cations other than Fe3+ showed that none of the studied cations interfered with Fe3+. Practical application of TPE-TAP was also carried out using a commercial iron drug. All results showed that TPE-TAP is a fluorometric sensor highly selective, sensitive, and suitable for practical application for Fe3+ ions in aqueous medium.

Evaluation the binding of chlorogenic acid with bovine serum albumin: Spectroscopic methods, electrochemical and molecular docking

Chlorogenic acid(CGA) is the common active phenolic acid in Chinese medicinal materials such as honeysuckle and eucommia. It is a class of small molecules with multiple activities such as antioxidant, inhibiting cancer cells, lowering blood sugar and lowering blood pressure. In this paper, UV–vis spectroscopy, fluorescence spectroscopy, circular dichroism, molecular dynamics simulation and cyclic voltammetry (CV) electrochemical analysis were used to investigate the mechanism about interaction between CGA and BSA. Based on fluorescence quenching analysis, CGA quenched the inherent fluorescence of BSA remarkably through a static mechanism. The obtained value of binding constant (Kb = 5.75 × 105 L·mol−1) revealed a high binding affinity between CGA and BSA. The simulated molecular docking showed that hydrophobic force were also involved in the interaction between BSA and CGA. This paper also investigate the effect of temperature and metal ions on the binding of CGA and BSA. When the temperature increased, the binding of BSA and CGA was destroyed. Metal ions affect both the structure of BSA and the combination of BSA and CGA. By studying the mechanism of CGA interaction with BSA, we elucidated the storage and transport mechanism of CGA in vivo under simulated human environment and temperature conditions.

Soil humic acid and arsenite binding by isothermal titration calorimetry and Dynamic Light Scattering: Thermodynamics and aggregation

The arsenite-humic acid binding process was investigated using Isothermal Titration Calorimetry (ITC), Dynamic Light Scattering and Laser Doppler Electrophoresis techniques. The ITC data were successfully (R2 = 0.996–0.936) interpreted by applying the MNIS model, enabling thermodynamic parameters to be determined. The MNIS model was adjusted to the arsenite-HA binding process assuming that hydrogen bonding is the dominant type of interaction in the system. Negative enthalpy change values indicated the arsenite-HAs binding as an exothermic process. Negative ΔG values (-(26.83–27.00) kJ mol−1) pointed out to spontaneous binding reaction, leading to the formation of the arsenite-HA complexes. The binding constant values ((7.57–5.02) 105 M−1) clearly demonstrate pronounced binding affinity. As ΔS values are obviously positive but close to zero, and ΔH>ΔS, the reaction can be considered enthalpy driven. Reaction heats and ΔH values (-(18.96–15.64) kJ mol−1) confirmed hydrogen bonds as the most ascendant interaction type in the arsenite-HA complex. Negative zeta potential values (−45 to −20 mV) had shown that arsenite-HA aggregates remained negatively charged in the whole molar charge ratio range. The HAs' aggregate size change is evident but not particularly pronounced (Zav = 50–180 nm). It can be speculated that aggregation during the titration process is not expressive due to repulsive forces between negatively charged arsenite-HA particles. Thermodynamic and reaction parameters clearly indicated that arsenite-HA complexes are formed at common soil pH values, confirming the possible influence of humic acids on increased As mobility and its reduced bioavailability.

Formulation and evaluation of a novel megalomeric microemulsion from tamarind seed xyloglucan-megalosaccharides for improved high-dose quercetin delivery

Megalomeric microemulsion is a new term referring to lipid-based formulation using amphiphilic megalosaccharide as a coexcipient. Quercetin is a dose-dependent bioactive compound and has promising therapeutic potential, but its low water solubility and permeability restrict its treatment efficacy. We aimed to formulate high-dose quercetin loaded into colloidal micelles by the self-micro emulsifying system (SMES) in combination with Tween 80, isopropyl myristate, and xyloglucan megalosaccharide (X-MS). X-MS is a moderate-size heterologous saccharide obtained from enzymatic cleavage of tamarind seed xyloglucan. X-MSs with an average degree of polymerization of 16 and 56 were investigated to bearing their surface hydrophobic interaction with a fluorescence probe 6-(p-toluidino)-2-naphthalene-6-sulfonate yielded the binding constant values of 127 and 180 M−1, respectively and X-MS itself displayed a slight effect on quercetin binding. However, the implementation of X-MSs toward SMES was highly compatible because X-MS molecules were confined in micellular solutions. Consequently, X-MSs improved the quercetin loading from 1 to 2 to 12.5–17.7 mg/mL based on the composition ratio, X-MS chain lengths, and X-MS concentrations (0.15–3.0%, w/v) and stabilized the quercetin-loaded oil-in-water SMES. The optical appearances were transparent yellow containing uniformly fine droplets with diameters of 11–12 nm. In vitro radical scavenging activity tests with 2,2-diphenyl-1-picrylhydrazyl showed that the megalomeric microemulsions improved the half-maximal inhibitory concentration (IC50 = 22–24 μg/mL) over that of the X-MS-free microemulsion. This study provided a new approach of liquid supplementation from commercially unavailable-size xyloglucan to be a promising added-value agent for oral uptake of quercetin.

Electroanalysis of Ibuprofen and Its Interaction with Bovine Serum Albumin.

The current work presents a sensitive, selective, cost-effective, and environmentally benign protocol for the detection of ibuprofen (IBP) by an electrochemical probe made of a glassy carbon electrode modified with Ag-ZnO and MWCNTs. Under optimized conditions, the designed sensing platform was found to sense IBP up to a 28 nM limit of detection. The interaction of IBP with bovine serum albumin (BSA) was investigated by differential pulse voltammetry. IBP-BSA binding parameters such as the binding constant and the stoichiometry of complexation were calculated. The results revealed that IBP and BSA form a single strong complex with a binding constant value of 8.7 × 1013. To the best of our knowledge, this is the first example that reports not only IBP detection but also its BSA complexation.

Influence of Steric and Electronic Effects in Structure‐Activity Relationships of Schiff Base Ligands: Green Synthesis, Characterization, DFT/TD‐DFT Calculations, Molecular Docking and Biological Studies

AbstractThree novel Schiff base ligands derived from 2‐(benzylthio) aniline and substituted benzaldehydes, i. e., 3,5‐di‐tert‐butyl‐2‐hydroxybenzaldehyde, 3,5‐dibromo‐2‐hydroxybenzaldehyde, and 2‐hydroxy‐4‐methylbenzaldehyde, respectively were synthesized in almost quantitative yields employing environmentally friendly techniques such as microwave‐assisted reaction and green solvents. To explicate all the structural and characteristic attributes of synthesized ligands, a combined experimental and theoretical investigation was done. The experimental characterization was conducted by applying elemental analysis, FT‐IR, 1H‐NMR, 13C‐NMR, ESI‐MS, and UV‐Vis spectroscopy. The theoretical calculations of optimized energy, geometrical parameters, electronic spectra, natural atomic charges, 3D plots of MEP, and vibrational wavenumbers were computed and elucidated using DFT and TD‐DFT methods. The calculations were performed by employing B3LYP/6‐311+G(d,p) level. In‐vitro DNA binding affinity of the ligands was studied by UV‐Vis spectroscopy, fluorescence spectroscopy, and molecular docking. The binding constant values obtained for ligands A−C were 3.26×103 M−1, 1.43×104 M−1, and 4.95×103 M−1, respectively. Moreover, the bioactivities of these ligands were probed for their in‐vitro antioxidant and anti‐inflammatory activities. Interestingly, in both the activity ligand C was found to be more biologically potent. A molecular docking investigation was also performed to acquire more information about the binding mode and energy.

Experimental and biophysical interaction studies of alanine modified polyaniline with bovine serum albumin and human serum albumin: Influence of alanine modification on the spectral, morphological and electronic properties

The present work reports for the first time, modification of aniline with alanine (Ala) in mole ratios of 80–20, 50–50 and 20–80 via ultrasound-assisted polymerization. The formation of Ala-incorporated polyaniline (PANI) was confirmed via FTIR, UV–visible and SEM studies. The geometry optimization, Mulliken charge distribution, vibrational as well as electronic spectral analysis was carried out using Gaussian 09 software with B3LYP/6311 G(d) basis set. Quenching of bovine serum albumin (BSA) and human serum albumin (HSA) by Ala/PANI followed the static mechanism which was confirmed by the fluorescence studies and Stern Volmer plots. The binding constant (Kb) values were found to be higher for Ala-PANI oligomers (∼105 LM−1) containing higher loading of PANI. The binding affinity of Ala/PANI towards BSA as well as HSA was found to be fairly good and the docking studies established that hydrogen bonding as well as Van der Waal’s forces played a significant role in the binding process.

Investigation of an anaesthetic drug (tetracaine hydrochloride) in the presence of ionic fluid and surfactant: Mixed micellization & spectroscopic studies

The effect of ionic liquid and cationic surfactant on the physicochemical characteristic of an anaesthetic drug (tetracaine hydrochloride, TCH) has been studied in the current task. The ionic fluid (1-hexadecyl-3-methyl imidazolium chloride, SAIL) and cationic surfactant (cetylpyridinium chloride, CPC) used in this study are of the same hydrophobic chain length. Tensiometric and absorption spectroscopic methods have been castoff to study the interaction of TCH with SAIL/CPC. The critical micelle concentration (cmc) values of single and mixed amphiphiles were computed by the surface tension method. In addition to cmc, maximum surface excess concentrations (Γmax), minimum surface areas per surfactant molecule (Amin), surface tension at the cmc (γcmc), surface tension reduction efficiency (πcmc), and several thermodynamic parameters of mixed micellization were measured. The calculated average value for the interaction parameter (βRub) suggests TCH show higher synergistic interaction with SAIL compared to CPC. The better attractive interaction (synergism) between SAIL and TCH is also confirmed by UV–visible spectroscopy. The absorption spectra of the drug show increase in the absorption with increasing the concentration of surfactants without any shift confirming the formation of a new complex. The binding constant value is more for the TCH + SAIL mixture.

Study of structure of nonaqueous reverse micelles with o-nitroaniline and methyl orange as molecular probes: comparison with an aqueous reverse micelles

Abstract Instead of water reversed micelles can also be formed with polar organic solvents possessed with high dielectric constant and very low solubility in oil phase. Nonaqueous reverse micelles or microemulsions represent an interesting microreactors for various reactions, especially for reactions, where reagents can react with water. Study of localization places of molecular probes in organic polar pockets of reverse micelles is topical. The solvatochromic behavior of optical probes ortho-nitroaniline (o-NA) and methyl orange (MO) was studied in nonaqueous reverse micelles on the basis of surfactants sodium bis (2-ethylhexyl) sulfosuccinate (AOT) and polyoxyethylene (4) lauryl ether (C12E4) and polar organic solvents (acetonitrile, dimethylformamide, glacial acetic acid, etc.) insoluble in oil phase hexane. The strength of binding of o-NA and MO to AOT and C12E4 reversed micelles was assesssed via binding constant (K b ) and association degree (α) respectively. Donor, acceptor, or dipole-dipole interactions ability of the solvent to the head groups of surfactant was taken into account in order to explain results obtained with UV–visible spectroscopic method. The binding constants of o-NA with reverse AOT micelles in the presence of various solvents in the pockets of reversed micelles increase in the following row water < glacial acetic acid < acetonitrile < dimethylformamide < dimethyl sulfoxide, but this sequence is reversed when o-NA binds to C12E4 reverse micelles. The high value of the proton donor or acidity parameter in the water molecule (x d = 0.37) determines the weak binding of o-NA to the head AOT groups (K b = 20.8) in case of aqueous reverse micelles. The high value of the dipole parameter in the dimethylformamide molecule (x n = 0.40) promotes its strong interaction with nonionic polyoxyethylene groups of C12E4, which results in low value of binding constant (K b = 26.5) in case of optical probe o-NA and low value of association degree (α = 0.60) using MO as absorption probe. The results of this article will contribute to the improvement of the concept of interfacial processes, viz.: (i) some issues of supramolecular chemistry, (ii) revealing the contribution of parameters of donor, acceptor or dipole-dipole interaction in a polar organic solvent at the surfactant/nonpolar organic solvent interface, and (iii) features of the dissolution of optical probes in non-aqueous reverse micelles.

Purine-based Schiff base Co(II), Cu(II), and Zn(II) complexes: Synthesis, characterization, DFT calculations, DNA binding study, and molecular docking

A series of metal complexes of Co(II), Zn(II), and Cu(II) of purine base Schiff base ligand L1 6,6′-((1E,1′E)-((7H-purine-2,6-diyl)bis(azanylylidene))bis(methanylylidene))bis(2-methoxyphenol) and L2 3,3′-((1E,1′E)-((7H-purine-2,6-diyl)bis(azanylylidene))bis (methanylylidene))bis(4H-chromen-4-one) were synthesized. The characterization of synthesized compounds was investigated through elemental analysis, UV–vis, FT-IR, NMR, and mass spectrometry. The spectroscopic and DFT studies validate the coordination of ligand to the metal centers along with their structural details. In complexes of L1 and L2, the N and O atoms coordinate to metal centers of zinc, cobalt, and copper. However, in the case of L1 complexes the binding mode of oxygen is through phenolic –OH of vanillin moiety. In contrast, complexes of L2 the binding mode of oxygen source is carbonyl oxygen of chromone carboxaldehyde moiety. The stability order follow- ZnL1 < CoL1 < CuL1 < CuL2 < CoL2 < ZnL2. The CT-DNA binding activity of all synthesized complexes with the help of UV–vis absorption titration, fluorescence titration, and viscosity measurement was studied. In both cases, cobalt complexes of L1 and L2 showed high DNA binding activity. The binding constant values are in the order of 105 via intercalation mode of binding. The molecular docking study was performed to speculate on the active binding site between metal complexes and CT-DNA.