Binding Constant Values Research Articles

Exploring diaminomaleonitrile-derived Schiff base ligand and its complexes: Synthesis, characterization, computational insights, biological assessment, and molecular docking

A tetra dentate ONNO donor diaminomaleonitrile-based Schiff base ligand along with its four new complexes of Co(II), Ni(II), Cu(II), and Zn(II) have been synthesized. The computational approach has been utilized to provide a theoretical framework for understanding the electronic structure and properties of these complexes. The distorted octahedral geometry of the Schiff base metal complexes indicates that the metal ions are coordinated with the ligand through ONNO donor sites, which is further confirmed by characterization using physiochemical and spectroscopic techniques like elemental analysis, mass, electronic, infrared, 1H, and 13C spectra. In addition, magnetic behavior is analyzed using the Vibrating Sample Magnetometer(VSM). To evaluate the potential modes of biomolecular interactions with the synthesized complexes utilizing Deoxyribo Nucleic Acid(DNA) and to assess the corresponding binding constants, an absorption spectroscopic technique has been utilized. Metal complexes are reported to have a range of binding constant values from 5.45 × 104 M−1 to 4.35 × 105 M−1 with different binding modes, such as intercalation, mixed mode, and electrostatic contact. In addition, in-vitro tests for antibacterial and anti-inflammatory activity have been employed to assess the bioactivities. With an IC50 value of 209.24 µg/mL, the Zn(II) complex is found to show considerable anti-inflammatory action as well as has superior antibacterial activity among all other complexes. The existence of electron-withdrawing CN groups together with other factors can be accounted for biological activity in our reported complexes. Further, molecular docking simulations are conducted to gain insights into the molecular-level interactions and to determine the potential binding energies of inhibitors whose results are in consistent with the in-vitro investigations.

Salicylaldehyde-diphenyl-azine skeleton-based ESIPT-coupled AIEgens with tunable emission and applicable as highly selective and sensitive Cu2+ ion sensor

Herein, we are reporting four novel salicylaldehyde-diphenyl-azine (SDPA) skeleton-based luminogens with tunable emission synthesized using the microwave. The photophysical studies in different solvents and acetonitrile/water fractions (fw= 0–90%) elucidate that they feature ESIPT and AIE characteristics. Further, they demonstrate colorimetric and fluorometric sensing for Cu2+ ions selectively and sensitively. The AIEgens responds TURN-OFF emission in the presence of Cu2+, having LOD values in the nanomolar range (4.4–12.1 nM), much lesser than the limit defined by US-EPA. The high values of binding constants (Ka) show strong binding, which is attributed to the paramagnetic nature of Cu2+ ions. The binding stoichiometry of the compounds and the Cu2+ ions were determined to be 2:1 using Job's plot and DFT analysis. The practical utilities of the proposed AIEgens have been analyzed by spiking Cu2+ in water samples from different sources. In conclusion, our study demonstrates that changing the substituents (electron-withdrawing in BSDPA and DBSDPA & electron-donating in DTSDPA and MSDPA) on the salicylaldehyde does not affect the selectivity and sensitivity towards Cu2+ ions. Instead, it significantly tunes emission properties towards the longer wavelength region (up to 50 nm in MSDPA compared to the unsubstituted SDPA). Overall, this study presents an environmentally benign and convenient approach, which opens up new avenues in synthesizing highly selective and sensitive red/NIR emissive AIEgens for Cu2+ ions by modifying appropriate substituents.

Exploring the photophysical interaction of xanthene dyes with gold nanorods by optical spectroscopic techniques and in-vitro cytotoxicity studies of dye-nano conjugates

The current study investigates the photophysical interactions of xanthene dyes such as fluorescein (FL) and rose bengal (RB) dyes with cetyltrimethylammonium bromide stabilized gold nanorods (CTAB-AuNRs) using optical spectral techniques, and computational interaction analyses. When xanthene dyes are conjugated with CTAB-AuNRs, significant modifications in their optical spectroscopic characteristics are found. In the absorption spectrum analyses of dye-AuNRs systems, the appearance of longitudinal plasmon resonance bands and the hypochromic behavior of xanthene dyes were observed in response to the interaction of CTAB-AuNRs. The gathered extinction spectral results indicated that there were significant electrostatic interactions between the positively charged CTAB-AuNRs and the negatively charged xanthene dye molecules. At the same time, the substantial quenching with a reduced quantum yield of the dye molecules is shown in the emission spectra of xanthene dyes with CTAB-AuNRs. The strong electrostatic interactions and ground state complex between xanthene dyes and CTAB-AuNRs have been suggested as the mechanism of emission quenching. The results of the emission quenching are supported by the calculated high binding constant values. Additionally, the results of computational interaction investigations also demonstrate the near closeness of xanthene dye molecules and CTAB-AuNRs. Finally, the cytotoxicity of free dyes and dye-nanoconjugates was next tested against breast (MCF-7) and lung (A-549) cancer cells. All the tested samples exhibit significant antiproliferative activity against MCF-7 and A-549 cancer cells. These cytotoxic study results showed that cells treated with xanthene dyes were less sensitive than FL-AuNRs and RB-AuNRs dye nanoconjugates.

Ascorbic and salicylic acids modulate the binding interactions of an emergency contraceptive pill levonorgestrel to a model transport protein: Insights from spectroscopy and molecular docking analysis

Serum proteins generally help to transport and distribute drug molecules within the body. In this study, the binding characteristics of bovine serum albumin (BSA) with levonorgestrel (LVG), an emergency contraceptive pill, and the influences of ascorbic acid (ASC) and salicylic acid (SAL) on the binding behaviour and protein structure were elucidated using multi-spectroscopic techniques and molecular docking. The results showed that levonorgestrel decreased BSA intrinsic fluorescence via static quenching mechanism. Binding constant (Ka) values for BSA-LVG complexes were 103 to 104 M-1, indicating their high stabilities. Site probing/docking analysis indicated LVG bound between BSA subdomains IIA and IIIA. UV–visible absorption, Fourier Transform-Infrared and 3D fluorescence spectroscopies affirmed LVG-induced changes in BSA structure, especially in α-helix and β-sheet contents. ASC and SAL influenced BSA conformation for LVG binding and reduced the Ka values by 3.37 and 5.43-folds, respectively. LVG altered the microenvironments of tyrosine residues, interacted with Arg-217, Lys-221, Val-292, Glu-443 etc. within the binding domains. The process was spontaneous (ΔG<0), entropy driven (TΔS>ΔH) and involved van der Waals forces and hydrogen bonding. The findings of the study offered details on the binding interaction between BSA and LVG, and also indicated that prior intake of ASC or SAL could suppress the binding affinity of BSA for levonorgestrel.

Selective recognition of Zn(II) by a novel Schiff base chemosensor with the formation of an AIE active Zn(II) complex having picric acid detection ability: Application in live cell imaging study

The present work highlights the development and spectroscopic identification of a Schiff base chemosensor, (Z)-4-bromo-2-(((1-methoxybutan-2-yl)imino)methyl)phenol, (HL), for selective detection Zn(II) via turn-on fluorescence among a number of competing cations in a 9:1 DMSO-water media. The high binding constant value, measured during titration of HL and Zn(II), boosts to conduct a straightforward condensation reaction between HL and Zn(II) which results in solid crystals of Zn(II) complex (complex 1). In 7:3 DMSO-water media, complex 1 display Aggregation Induced Emission (AIE) behavior, as a result of which, with increasing the water percentage, under UV light optically the cyan color complex 1 solution converts to green color with the enhancement of fluorescence intensity. The UV, fluorescence, DLS, and SEM studies, fully approve the probe's AIE active behavior. The AIE active property of complex 1 is implemented to detect picric via turn-off fluorescence. The chelation-induced enhanced fluorescence (CHEF) on and Excited state internal proton transfer (ESIPT) off are the key factors in showing the luminescence property of complex 1 and the distortion of aggregation behavior of complex 1 in the presence of picric acid leads to the turn-off fluorescence of the complex 1 solution. The mass spectral and IR spectral analysis supports the 1:1 stoichiometric addition of the probe and analyte and the structure of the probe-analyte complexes is optimized using density Functional Theory (DFT) study. Finally, the live cell imaging study enables us to independently verify the biosensing behavior of complex 1 and HL towards Zn(II) and picric acid respectively.

Supramolecular Detection of a Sub-ppm Nerve Agent Simulant by a Smartphone Tool.

The widespread use of smartphones and related tools is extending their applications in several fields. Herein, we report a reusable smartphone coupled portable detection system for the sensing of sub-ppm level of a nerve agent mimic (dimethylmethylphosphonate) in the gas phase. The detection system is based on multiple hydrogen-bond interactions of the vapor analyte with an ad-hoc functionalized Bodipy chromophore scaffold. The multitopic approach used for the molecular recognition of DMMP leads to the highest binding constant values, high selectivity, and low limits of detection.

Comparative analysis of the capability of the extended biotic ligand model and machine learning approaches to predict arsenate toxicity

Assessment of inorganic arsenate (As(V)) is critical for ensuring a sustainable environment because of its adverse effects on humans and ecosystems. This study is the first to attempt to predict As(V) toxicity to the bioluminescent bacterium Aliivibrio fischeri exposed to varying As(V) dosages and environmental factors (pH and phosphate concentration) using six machine learning (ML)-guided models. The predicted toxicity values were compared with those predicted using the extended biotic ligand model (BLM) we previously developed to evaluate the toxic effect of oxyanion (i.e., As(V)). The relationship between the variables (input features) and toxicity (output) was found to play an important role in the prediction accuracy of each ML-guided model. The results indicated that the extended BLM had the highest prediction accuracy, with a root mean square error (RMSE) of 12.997. However, with an RMSE of 14.361, the multilayer perceptron (MLP) model exhibited quasi-accurate prediction, despite having been trained with a relatively small dataset (n = 256). In view of simplicity, an MLP model is compatible with an extended BLM and does not require expert knowledge for the derivation of specific parameters, such as binding fraction and binding constant values. Furthermore, with the development and employment of reliable in-situ sensing techniques, monitoring data are expected to be augmented faster to provide sufficient training data for the improvement of prediction accuracy which may, thus, allow it to outperform the extended BLM after obtaining sufficient data.

Investigation of Chloride Anion Binding Properties of Glipizide Drug

This study addresses the anion binding property of Glipizide (GLP), an oral antidiabetic a second-generation drug member of the sulphonylurea (SU) family. GLP effectively interacts with Cl- anion according to 1H-NMR spectroscopic titrations of successive tetrabutylammonium chloride (TBACl) in deuterated chloroform (CDCl3) and dimethyl sulfoxide (d6-DMSO). Upon the addition of TBACl, the change in chemical shift was observed for both N-H protons of SU in CDCl3, whereas it causes a difference in the shift of only one of N-H proton in SU in d6-DMSO. In addition, the data obtained from 1H-NMR spectroscopic titrations was analyzed by DynaFit program to calculate the binding constant (Ka) value between GLP and Cl- anion. It was found that GLP binds Cl- anion in CDCl3 with higher affinity (Ka=77.37 M-1, Fitplot for N-Hh proton at δ=6.47 ppm) than in d6-DMSO (Ka=38.53 M-1, Fitplot for N-Hh proton at δ=6.32 ppm).

Evaluation of calf thymus DNA binding of newly synthesize five 9 [sbnd]O[sbnd] Imidazolyl alkyl berberine derivative: A comparative multi-spectroscopic and calorimetric study

DNA binding with small molecule plays an important role in the designing of various anticancer drugs with greater efficacy. The five 9-O-imidazolyl alkyl berberine derivatives (BI) of different chain length has been synthesized and fully characterized. The binding study of calf thymus DNA with these newly synthesized berberine derivative was performed using various biophysical techniques. The binding affinity of BI to calf thymus DNA increased with increasing the chain length. The binding constant value obtained from UV–Vis spectral analysis was 1.84x105for BI1, 2.01x105for BI2, 1.51 × 106 for BI3, 3.66 × 106 for BI4, 6.68 × 106. Partial intercalative binding with strong stabilization of the DNA helix was revealed from circular dichroism spectral study and viscosity measurement. From the ITC experiment it was revealed that the bindings of BI1, BI2, BI3, BI4 and BI5 to calf thymus DNA were favoured by a large positive favourable entropy and negative enthalpy change and the highest spontaneity found for BI5. With the increase in chain length the binding was driven by a stronger entropy term with a higher binding constant indicates involvement of hydrophobic force for all these interaction. High binding affinities of calf thymus DNA with berberine-imidazole derivatives might be helpful for new drug design.

The Study of the Effect of Dimethylsulfoxide (or Diethylsulfoxide) on Quinine Sulfate-DNA Binding by UV-Vis and Steady-State Fluorescence Spectroscopies.

The effect of dimethylsulfoxide (DMSO) and diethylsulfoxide (DESO) on binding between quinine sulfate (QS) and DNA was studied by virtue of UV-Vis absorption, steady-state fluorescence spectroscopies, and fluorescence polarization measurements. The binding constant was determined at three different temperatures and the values of standard Gibbs energy change, enthalpy and entropy of binding were determined. The mechanism of binding and the effect of sulfoxides on this process was revealed. The values of binding constant, fluorescence polarization and iodide quenching studies confirmed that the main binding mode in QS-DNA system is groove binding. Addition of sulfoxides does not change the binding mechanism. Moreover, with addition of sulfoxides binding constant increases due to the removal of water molecules from DNA grooves making them more available for QS molecules.To explain the effect of DMSO and DESO on QS-DNA binding the photophysical properties of QS in aqueous solutions of DMSO and DESO were also studied. On the basis of quantum yield of QS in water, DMSO and DESO the types of intermolecular interactions were discussed. The obtained results show that quantum yield of QS in sulfoxides is lower compared with that in water and aqueous solution of 0.1M H2SO4. QS forms ground state complexes with both DMSO and DESO that are stronger fluorophores compared with free QS molecules.

A comprehensive assessment of interfacial and bulk properties of sodium dodecylsulfate via addition of competitive Hofmeister ions in presence of Cosolvent: A combined experimental and theoretical study

The synergistic interaction of sodium dodecyl sulphate (SDS) and added electrolyte in presence of cosolvent is investigated by determining the critical micelle concentration of SDS. The present system is carried out with two different types of counterions from Hofmeister series where Hofmeister chaotropic ion i.e. NH4+ is attracted more towards the negatively charged chaotropic dodecyl sulphate headgroup of SDS than the kosmotropic ion. To understand the thermodynamic behavior of SDS micelle, counterion binding constant values are measured using the well-established Corrin-Harkins or modified Corrin-Harkins equations. Various assessments of aggregation and adsorption phenomena of SDS micelle are established from both experimental and theoretical concepts. The exchange of counterion i.e. Na+ ion by NH4+ ions can occur at a particular electrolyte concentration where SDS micelle leads to the formation of ammonium dodecyl sulphate (AmDS) in the present cosolvent media. Therefore, the Hofmeister chaotropic ion (NH4+) is found to be a competitive ion. In addition to that, solvophobicity of the cosolvent mixture is another important parameter which could influence SDS micellization differently.

Supramolecular assembly of coumarin 7 with sulfobutylether-β-cyclodextrin for biomolecular applications.

Coumarins, in general, exhibit a wide range of photophysical characteristics and are highly sensitive to their microenvironment, and, therefore, their fluorescence characteristics have attracted immense attention as sensors in chemical and biological systems. In the present study, the supramolecular interaction of a bichromophoric coumarin dye, namely, Coumarin 7 (C7) with sulfobutylether-β-cyclodextrin (SBE7βCD) macrocyclic host at different pH conditions has been investigated by using optical spectroscopic techniques such as absorption, steady-state and time-resolved emissions, and circular dichroism measurements and compared with that of βCD. Considerable enhancement in the fluorescence intensity and lifetime of C7 on complexation with SBE7βCD proposes that non-radiative processes like TICT behavior are strictly hindered due to the confinement in the host cavity experienced by the C7 dye. The increase in the rotational correlation time evaluated from the fluorescence anisotropy decay kinetics further confirms the formation of tightly bound inclusion complexes. The binding constant values reveal that the monocationic form of dye at pH 3 shows ∼3 times stronger interaction with SBE7βCD than the neutral form of dye at pH 7 due to strong electrostatic cation-anion interaction. SBE7βCD:C7 exhibits an improved photostability and an upward pK a shift of 0.4 unit compared to the contrasting downward pK a shift of 0.5 with the βCD. The enhanced fluorescence yield and increased photostability have been exploited for bioimaging applications, and better images were captured by staining the Drosophila fly gut with the SBE7βCD:C7 complex. The enhancement in the binding interaction and the emission intensity were found to be responsive to external stimuli such as small competitive binders or metal ions and nearly quantitative dissociation of the complex was demonstrated to release the dye and would find stimuli-responsive applications.

Salicylaldehyde based Schiff base: synthesis, characterisation and application for selective electrochemical detection of Cu2+ in real samples

ABSTRACT A simple salicylaldehyde-based Schiff base 2,2'-((1,3-phenylenebis(azanylylidine))bis(methanylylidene))dipehnol (PAMD) was synthesised by condensation reaction between salicylaldehyde and benzene-1,3-diamine (2:1 ratio) and characterised by spectral techniques such as NMR, FTIR and HRMS, followed by investigation for its spectroscopic behaviour towards diverse metal ions using UV and fluorescence studies. PAMD was found to exhibit sensitivity towards Cu2+ only. The receptor PAMD was then explored for its electrochemical behaviour using cyclic voltammetry, which displayed an irreversible anodic peak at 1.00 V due to imine group. Furthermore, PAMD was subjected to differential pulse voltammetry, which exhibited a sensitive response for Cu2+ in the linear range of 0–3.8 μM with lowest detection limit of 0.03 μM. The complexation between PAMD and Cu2+ was also supported by large values of binding constant (1.3 × 105 M−1) and negative free energy change (ΔG∘ = -29.2 kJmol−1) obtained from Benesi–Hildebrand equation. The carbon paste electrode (CPE) modified with PAMD displayed a Nernstian response to Cu2+ in the concentration range from 1.0 × 10−6 to 1.0 × 10−1 M and lowest detection limit of 4.0 × 10−7 M. The PAMD-CPE was successfully applied for determination of Cu2+ content in real samples such as groundwater, soil, and food grains (wheat and rice).

Effect of antidiabetic drug metformin hydrochloride on micellization behavior of cetylpyridinium bromide in aqueous solution

Herein, the interaction of an antidiabetic drug, metformin hydrochloride (MHCl), and a cationic surfactant, cetylpyridinium bromide (CPB) is investigated in an aqueous medium. The critical micellar concentration (CMC) of CPB is estimated through conductivity experiments and found to be reduced on adding MHCl and further decreased in the presence of NaCl. The reduced CMC is attributed to the solubilization of MHCl by CPB through micellization and the micellization is found to be thermodynamically spontaneous that experiences an augmentation in the presence of NaCl. This is identified from the negative value of standard free energy ( Δ G0 m). The higher negative value of Δ G0 m (-55.41 kJ mol−1) for CPB + MHCl + NaCl than CPB (-37.89 kJ mol−1) and CPB + MHCl (-34.08 kJ mol−1) is suggestive of the above phenomenon. The positive values of Δ S0 m in all three cases confirm that the micellization is entropy driven. The binding of MHCl on CPB is quantified by estimating binding constant using the Benesi-Hildebrand (B-H) plot through UV-visible spectral methods. The binding constant values were calculated to be 2.70 M−1 for CPB + MHCl + NaCl compared to 1.258 M−1 for CPB + MHCl predicting a favoring of micellization in the presence of NaCl which is higher than that in the presence of co-solvents. The molecular interaction of MHCl and CPB is justified using FT-IR and NMR techniques. The surface properties of drug surfactant interactions are assessed using SEM techniques. The point of interaction between the drug and surfactant is visualized through the molecular docking approach. The results suggest that CPB would be an effective solubilizer for developing MHCl drug formulations. Communicated by Ramaswamy H. Sarma

Cucurbit[7/8]uril assisted modulations in the photophysical properties of 4′,6-diamidino-2-phenylindole dye

The influence of two versatile macrocyclic hosts, cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8), on the photophysical properties of a biologically important dicationic dye, 4′,6-diamidino-2-phenylindole (DAPI), has been investigated following different photophysical studies and quantum chemical calculations. Results indicate that while CB7 with having smaller cavity size forms only 1:1 dye-host inclusion complex with DAPI, the CB8 host with larger cavity size forms both 1:1 and 2:1 dye-to-host inclusion complexes with the dye. Quantum chemical studies indicate that while 1:1 complex is formed by inclusion of either the benzene or indole end of DAPI into a CBn cavity, the 2:1 complex in the DAPI-CB8 system is formed mainly by the inclusion of two benzene ends of two dye molecules into the host cavity, entering through opposite portals of the host. Estimated binding constant values for the dye-host complexes formed in these systems are found to be exceedingly high. Strong ion–dipole interaction of dicationic DAPI with polarizable CBn portals along with usual hydrophobic interaction arising from inclusion of the dye into the host cavity cooperatively provide the extremely high stability for the dye-host complexes formed in these systems. Overall, the results demonstrate that compatibility between the dye structure and the host cavity are mainly responsible for the differential bindings stoichiometries of the dye-host complexes formed in the studied DAPI-CBn systems. Further, these differences in the binding stoichiometries of the complexes are the main reason for the large differences observed in the modulated photophysical properties of the dye in the DAPI-CB7 and DAPI-CB8 systems. Since DAPI is an important fluorescence marker for several biomolecules, present results are having relevance to the applications of DAPI in various biophysical investigations.

Deciphering the calf thymus DNA binding potential of 5FU conjugated copper oxide nanoparticles along with its antiproliferative effects on liver cancer cells: A molecular, in silico, and in vitro approach

The current study accomplished 5-fluorouracil conjugated copper oxide nanoparticles (5FUcCuONPs) and assessed their DNA binding and antiproliferative capabilities using an array of in vitro techniques. The synthesized nanoparticles were characterized by UV-visible spectroscopy, dynamic light scattering, Fourier transform infrared spectroscopy, thermogravimetric analysis, and microscopic techniques. The DNA interaction analysis revealed that 5FUcCuONPs had a binding constant value in the range of 5.27 × 104 M−1, demonstrating an effective DNA binding interaction. The potency of the binding interactions was further corroborated by the Atomic Force Microscopic (AFM) analysis. Moreover, the intricate mechanism of the ligand-DNA interaction was investigated by molecular docking study, which revealed a binding energy of -6.3 kcal/mol. The 2D interaction plots of selected conformations revealed a network of hydrophobic and hydrogen bond interactions. Subsequent cell viability and the morphological study in HepG2 cells demonstrated the anticancer potential of 5FUcCuONPs with the IC50 value of 7.1μg/ml. This study demonstrates the DNA binding and therapeutic potential of 5-fluorouracil conjugated copper oxide nanoparticles, offering an intriguing alternative to combinatorial chemotherapy.

Voltammetric studies on the interaction of ds-DNA with anti-cancer agents imatinib and erlotinib – Comparison of Au and Pt nanoparticle effects to drug-DNA complex formation

The interactions of imatinib (IMA) and erlotinib (ERL) with calf-thymus double-stranded deoxyribonucleic acid (ds-DNA) were studied by using monometallic (Au and Pt) and bimetallic (Au + Pt) nanoparticles modified DNA biosensors. The prepared electrochemical biosensors were designed to show the interaction between IMA (or ERL) and ds-DNA. The characterization of the prepared sensors was carried out by energy-dispersive X-ray spectroscopy (EDX). The influence of Au, Pt, and Au + Pt nanoparticles in the modified biosensor was investigated to elucidate the interaction between the anti-cancer drugs and ds-DNA. The interaction was realized based on the electrochemical oxidation signal (at about +0.80 V) of the guanine (dGu) base of ds-DNA by differential pulse voltammetry (DPV) in pH 4.8 acetate buffer. The effect of the nanoparticle’s concentration and interaction time of IMA (and ERL) with ds-DNA on the electrochemical response of dGu were optimized. The results showed that Au + Pt nanoparticles, especially for IMA, significantly affected the binding constant value of the drugs to ds-DNA. Interaction studies have also shown that the binding mode for IMA and ERL could be intercalation and groove binding and the binding constant values were found to be 68.3 × 106 M−1 and 27.3 × 107 M−1, respectively.

Insights into the Self‐Filling Effects of Branched Isopropyl Groups on the Conformational and Supramolecular Properties of Isopropoxyprism[6]arene

AbstractIn this work, the direct macrocyclization of a prism[6]arene macrocycle bearing branched alkyl chains on the rims is reported. Isopropoxyprism[6]arene adopts in solution and in the solid state a cuboid D2‐conformation in which four isopropyl groups are folded inside the cavity, to give C−H⋅⋅⋅π interactions and filling the internal void. The conformational features of isopropoxyprism[6]arene have been studied by dynamic 1H NMR experiments. The presence of branched isopropyl chains on the prism[6]arene rims, stabilizes the cuboid D2‐conformation to a greater extent than ethyl or propyl groups in PrS[6]Et and PrS[6]nPr. The higher resistance of PrS[6]iPr to open its cuboid D2 conformation, with respect to PrS[6]Et and PrS[6]nPr, also affected its binding abilities. In fact, alkylammonium‐based endo‐cavity complexes of PrS[6]iPr show lower binding constant values than the analogous propoxy/ethoxy‐prism[6]arene complexes.

Exceptionally water-soluble [CuII2] complexes for investigating monosaccharide-metal ion interactions

The design, synthesis and characterization of two new dinuclear copper(II) complexes [Cu2(phpda)(µ-Cl)]·2H2O (1) and [Cu2(phpda)(µ-NO3)]·2H2O (2) (H3phpda = N,N′ -bis[2-pyridylmethyl]-2‑hydroxy-1,3-propanediamine-N,N′-dipropionic acid) as carbohydrate binding models have been reported. The FTIR, UV–Vis, ESI-MS, microanalysis and molar conductance data have been utilized to characterize the synthesized complexes. The structures of 1 and 2 have been established by density functional theory (DFT) calculations that exhibit a self-aggregated closely packed arrangement with average inter-metallic Cu···Cu separation of 3.2484 Å. In aqueous alkaline media, both complexes have been studied for their binding interactions with biologically important monosaccharides, d-glucose and d-glucosamine by employing UV–Vis spectroscopy and DFT calculations. The binding-assisted steady decrease of absorbances of 1 and 2 accompanied by a significant red/blue shift of absorption maxima of the complexes upon UV–Vis titration of 1 and 2 with d-glucose and d-glucosamine has been observed, suggesting 1:1 complex/monosaccharide interactions. Evaluation of binding constant values of monosaccharide-bound copper(II) complexes has been accomplished by utilizing UV–Vis titration data, and the values are found to be 2.145 × 103 M−1, 2.652 × 103 M−1, 1.388 × 103 M−1 and 1.793 × 103 M−1 for 1/D-glucose, 1/D-glucosamine, 2/D-glucose and 2/D-glucosamine assemblies, respectively. Fukui functions (fk+) on the copper sites, including HOMO and LUMO in both complexes have been obtained from DFT calculations to understand the likely copper sites involved in the binding events with monosaccharides. However, a comparative assessment of their binding constant values showed that d-glucosamine interacts with 1 and 2 more preferentially than d-glucose.

Synthesis, Antioxidant, Molecular Docking and DNA Interaction Studies of Metal-Based Imine Derivatives.

Currently, numerous ongoing studies are investigating the interaction of free radicals with biological systems, such as lipids, DNA and protein. In the present work, synthesis, characterization, antioxidant, DNA binding and molecular docking studies of Schiff base ligand and its Ni(II), Co(II), Cu(II) and Zn(II) were evaluated. The metal complexes have shown significant dose-dependent antioxidant activities higher than those of the free ligand but lesser than those of the standard antioxidant, ascorbic acid. The DNA binding constants (Kb) were found in the order Zn(pimp)2 {9.118 × 105 M-1} > H-pimp {3.487 × 105 M-1} > Co(pimp)2 {3.090 × 105 M-1} > Ni(pimp)2 {1.858 × 105 M-1} > Cu(pimp)2 {1.367 × 105 M-1}. Binding constants (Kb) values calculated from the molecular docking analysis were found to be in close agreement with the experimental results. The obtained results indicate the importance of synthesis complexes as a source of synthetic antioxidants and anticancer drugs.