Fluorescence investigation of the interaction of 2-(4-fluorophenyl)-1-phenyl-1H-phenanthro [9,10-d] imidazole with bovine serum albumin

Interactions of diclazuril enantiomers with serum albumins: Multi-spectroscopic and molecular docking approaches

In this work, multi-spectroscopic and molecular docking methods have been conducted in the investigation of enantioselective interactions between diclazuril enantiomers and human/bovine serum albumins (HSA/BSA). The binding constants between serum albumins (SAs) and diclazuril enantiomers revealed that SAs exhibited stronger binding affinity for (R)-diclazuril than (S)-enantiomer. In addition, the fluorescence quenching of SAs induced by diclazuril enantiomers was ascribed to static quenching mechanism, in which hydrogen bonds and Van der Waals forces were the main interactions. According to the thermodynamic study, binding of diclazuril enantiomers and SAs was an exothermic process driven by enthalpy change. Then, circular dichroism spectroscopy of SAs with diclazuril enantiomers revealed that the SAs conformation had changed in the presence of diclazuril. Moreover, molecular docking technology was applied in exploration of interactions between SAs and diclazuril enantiomers. The docking energy between SAs and (R)-diclazuril was larger than (S)-diclazuril, which indicated that the affinity of SAs with (R)-diclazuril was stronger than (S)-enantiomer. This work may provide valuable information for explaining differences in pharmacokinetics and residue elimination of diclazuril enantiomers in living organisms.

Anthracene-induced DNA damage and oxidative stress: a combined study at molecular and cellular levels

At present, research progress of anthracene's toxicity lags far behind the pollution caused on its application fields such as petroleum and minerals. In this paper, anthracene-induced oxidative stress effects and genetic toxicity were investigated at both the molecular and cellular levels. The intracellular oxidative stress effect of anthracene on earthworm primary coelomocyte was confirmed by the detection of reactive oxygen species, antioxidant enzymes activity, and malondialdehyde content. Moreover, after anthracene exposure, the decrease in the mitochondrial membrane potential and cell viability also indicated the adverse effects of anthracene on earthworm coelomocyte. The comet assay proved the break in DNA strand, revealing the anthracene-induced DNA damage. On the molecular level, we revealed that anthracene caused the shrinkage of the catalase skeleton and altered the microenvironment of chromophores of catalase by multi-spectral methods. Molecular simulation results indicated that anthracene interacted with His74 by "arene-arene" force and the dominant binding site between anthracene and catalase was close to the active site of catalase. In addition, anthracene was shown to bind to the DNA molecule by groove binding mode. This study proposed a new combined analysis method for the toxicity evaluation of anthracene at the cellular and molecular levels. Graphical abstract This study creatively proposed a new combined analysis for the toxicity evaluation of ANT at the cellular and molecular levels.

Exploring the influence of silver and lead on structure and function of xylanase: spectroscopic and calorimetric methods

Soil contamination with heavy metal could induce the alteration of soil ecological environments, and soil enzyme activities are sensitive indicators for the soil toxicology. Xylanase is one of predominant soil enzymes related to carbon nitrogen cycle. In this work, we explored the underlying mechanisms for conformational and enzymatic activity alterations of xylanase after silver and lead exposure at molecular level with systematical measurements including multiple spectroscopic methods, isothermal titration calorimetry, and enzymatic activity. Both silver and lead could loosen and unfold the skeleton of xylanase with the quenching of endogenous fluorescence. Silver interacted with xylanase forming larger-size aggregations through Van der Waals forces and hydrogen bonding, while lead interacted with xylanase forming larger-size aggregations through hydrophobic force. Silver and lead induced an obvious loss (67.1 and 56.31%) of the xylanase enzymatic activity, but silver has a greater impact on xylanase than that of lead. The xylanase enzymatic activity significantly decreased due to the conformational alterations. The negative effect of silver exposure on xylanase structure and function was more prominent than that of lead.

Investigation on the interaction of food colorant Sudan III with bovine serum albumin using spectroscopic and molecular docking methods

Sudan III is a coloring agent used in chemical industries and food additives. This article uses spectroscopic and molecular docking methods to investigate the interaction of Sudan III with bovine serum albumin (BSA) under a physiological condition. Spectroscopic analysis of the emission quenching revealed that the quenching mechanism of BSA by Sudan III was static. The binding sites and constants of Sudan III-BSA complex were observed to be from 0.72 and 6.41 × 10² L·mol^-1 to 0.69 and 5.83 × 10² L·mol^-1 at 298 and 310 K, respectively. The enthalpy change (ΔH) and entropy change (ΔS) revealed that van der Waals forces and hydrogen bonds stabilized the Sudan III-BSA complex. Energy transfer from tryptophan to Sudan III occurred by a fluorescence resonance energy transfer mechanism, and the r distance (3.32 nm) had been determined. The results of UV-Vis absorption, synchronous, three-dimensional fluorescence, and circular dichroism spectra showed that Sudan III induced conformational changes of BSA. Molecular docking studies revealed that Sudan III situated within subdomain IIA of BSA. A study on the interaction between Sudan III and BSA was of fundamental importance for providing more information about the potential toxicological effect of chemicals at the molecular level.

Multispectral and computational probing of the interactions between sitagliptin and serum albumin

The binding of sitagliptin (SIT), an anti-diabetic drug, to human and bovine serum albumin (HSA and BSA; main serum transport proteins) was investigated using various spectroscopic and molecular docking techniques. The fluorescence data demonstrated that SIT quenched inherent fluorescence of these proteins through the formation of SIT-HSA/BSA complexes. The number of binding sites was obtained (~1) and binding constant (K_b) and effective quenching constant (K_a) were calculated as 10⁴ for both systems. Based on thermodynamic parameters, the van der Waals forces and hydrogen bonding were the most important forces in the interactions between HSA/BSA and SIT, and the complex formation processes were spontaneous. The results of UV-vis absorption and FT-IR spectroscopic revealed that SIT induces small conformational changes in the structure of the proteins (HSA/BSA). The synchronous fluorescence (SF) spectroscopy demonstrated that the binding of SIT with HSA/BSA had no effect on the polarity around Trp and Tyr residues. The CD spectra showed changes in the secondary and tertiary structures of both proteins with a decrease in α-helices contents and an increase in β-turn structures. The molecular docking and spectroscopic data verified the binding mechanisms between SIT and HSA/BSA, and revealed that SIT completely fits into the hydrophobic cavity between domain II and domain III of these proteins.

Binding mechanism of maltol with catalase investigated by spectroscopy, molecular docking, and enzyme activity assay

Maltol is a flavor additive that is widely used in the daily diet of humans, and its biosafety attention is concomitantly increasing. Catalase (CAT) is an antioxidant enzyme to maintain homeostasis in the tissue's environment of human body and protect cells from oxidative damages. The adverse effects of maltol to CAT activity within mouse hepatocytes as well as the structural and functional changes of CAT on molecular level were investigated by multiple spectroscopy techniques, enzyme activity experiments, and molecular docking. Results suggested that when the maltol concentrations reached to 8 × 10^-5 mol L^-1 , the viability of hepatocytes decreased to 93%, and CAT activity was stimulated by maltol to 111% than the control group after exposure for 24 hours. Changes in CAT activity on molecular level were consistent with those on cellular level. The fluorescence quenching of CAT by maltol was static with the forming of maltol-CAT complex. Moreover, ultraviolet-visible (UV-visible) absorption, synchronous fluorescence, and circular dichroism (CD) spectra reflected that the presence of maltol caused conformational change of CAT and made the CAT molecule skeleton loose and increased α-helix of CAT. Maltol mainly bound with CAT through hydrogen bond, and binding site that is near the heme ring in the enzyme activity center did not interact with its main amino acid residues. This study explores the combination between maltol and CAT, providing references for evaluating health damages caused by maltol.

Insights into the effect and interaction mechanism of bisphenol S on lipids hydrolysis in sludge through multi-spectra, thermodynamics, and molecule docking analysis

As an alternative to bisphenol A, bisphenol S (BPS) is widely used in industrial production and daily life, which is then discharged into sewage treatment plants and accumulates in sludge. In this research, impact and interaction mechanism of BPS on lipids hydrolysis in sludge is studied from the respect of soluble organic matter and volatile organic fatty acids (VFAs). Multi-spectra, thermodynamics, molecule docking, and enzyme activity assay are applied to elucidate the effect mechanism of BPS on lipids hydrolysis. Results show that lipids hydrolysis is restrained due to the denaturation of lipase with BPS exposure. The interaction mechanism is involved in hydrophobic bond and hydrogen bond interaction in the activity region of lipase. This interaction not only results in an unfolding skeleton structure of lipase and a less hydrophobic microenvironment of tyrosine and tryptophan residues but also leads to fluorophore static quenching with the formation of lipase-BPS complex. The experimental results and the combined research methods not only contribute to the development of novel technique for sludge treatment containing micropollutant but also profit to clarify the interaction mechanism between other micropollutant and enzymes.

An exploration of the effect and interaction mechanism of bisphenol A on waste sludge hydrolysis with multi-spectra, isothermal titration microcalorimetry and molecule docking

An increasing amount of bisphenol A (BPA) is being produced and used, then discharged into sewage treatment plants and accumulated in sludge or soil, when the sludge is used as fertilizer. Accumulation of BPA in sludge or soil causes poisoning to the enzyme, which affects the biological treatment of sludge and the circulation and conversion of materials in soil. In this research, effect of BPA on sludge hydrolysis is studied from the respect of concentration and components of soluble organic matter in sludge, using three-dimensional fluorescence spectra. In order to illuminate the interaction mechanism, toxic effect of BPA on α-Amylase (a model of hydrolase in sludge) is investigated with multi-spectra, isothermal titration microcalorimetry and molecule docking at the molecular level. Results show that the secondary structure of α-Amylase and the microenvironment of amino acid residue in α-Amylase are changed. The molecular docking study and ITC results show that hydrophobic bond and hydrogen bond exist in the interaction between BPA and α-Amylase. Based on the above analysis and enzyme activity assay, sludge hydrolysis is inhibited due to the denaturation of α-Amylase with BPA exposure.

Fluorescence quenching study of 2,6-bis(5-(4-methylphenyl)-1-H-pyrazol-3-yl)pyridine with metal ions

A novel bispyrazole derivative 2,6-bis(5-(4-methylphenyl)-1-H-pyrazol-3-yl)pyridine was synthesized and its structure was confirmed by (1)H NMR, FTIR, MS techniques and elemental analysis. The binding interactions of BMPP with Cd(2+), Co(2+), Pb(2+) and Cu(2+) ions were investigated in MeOH-H2O solution by fluorescence quenching technique at two temperatures (25 and 35°C). Their quenching constants KSV, binding constants K, binding sites n and thermodynamic parameters (ΔH, ΔG and ΔS) were determined. The results indicated that the metal ions quenched the intrinsic fluorescence of the bispyrazole by forming the bispyrazole-metal complexes and their quenching process was a static quenching mechanism. In addition, the process of interaction was spontaneous and mainly ΔS-driven.

Study on the interaction characteristics of cefamandole with bovine serum albumin by spectroscopic technique

The interaction of cefamandole with bovine serum albumin (BSA) was studied by fluorescence quenching in combination with UV-Vis spectroscopic method under near physiological conditions. The fluorescence quenching rate constants and binding constants for BSA-cefamandole system were determined at different temperatures. The fluorescence quenching of BSA by cefamandole is due to static quenching and energy transfer. The results of thermodynamic parameters, ΔH (-268.0 kJ mol(-1)), ΔS (-810.0 J mol(-1) K(-1)) and ΔG (-26.62 to -8.52 kJ mol(-1)), indicated that van der Waals interaction and hydrogen bonding played a major role for cefamandole-BSA association. The competitive experiments demonstrated that the primary binding site of cefamandole on BSA was located at site III in sub-domain IIIA of BSA. The distance between cefamandole and a tryptophane unit was estimated to be 1.18 nm based on the Förster resonance energy transfer theory. The binding constant (KA) of BSA-cefamandole at 298 K was 2.239×10(4) L mol(-1). Circular dichroism spectra, synchronous fluorescence and three-dimensional fluorescence studies showed that the presence of cefamandole could change the conformation of BSA during the binding process.

Multiple linear regression solvatochromic analysis of donar-acceptor imidazole derivatives

Catalytic synthesis of some polysubstituted imidazoles under solvent-free condition is reported and their characterization has been carried out spectral techniques. Electronic spectral studies reveal that their solvatochromic behavior depends both the polarity of the medium and hydrogen bonding properties of the solvents. Specific hydrogen bonding interaction in polar solvents modulated the order of the two close lying lowest singlet states. The solvent effect on absorption and emission spectral results has been analyzed by multiple parametric regression analysis. Solvatochromic effects on the emission spectral position indicate the charge transfer (CT) character of the emitting singlet states both in a polar and a non polar environment. The fluorescence decays for the imidazoles fit satisfactorily to a bi exponential kinetics. These observations are in consistent with quantum chemical calculations.

Kamlet-Taft and Catalán solvatochromism of some π-expanded phenanthrimidazole derivatives - DFT analysis

Some π-expanded phenanthrimidazole derivatives have been synthesised and characterised by different spectral techniques. Kamlet-Taft and Catalán solvatochromism of synthesised phenanthrimidazole derivatives have been analysed. Non-linear optical (NLO) and natural bond orbital (NBO) analysis have been made by ab initio method to show intramolecular interactions. The energies of the HOMO and LUMO levels, the molecular electrostatic potential (MEP) energy surface, NBO studies have exploited the existence of intramolecular charge transfer (ICT) within the molecule.

Binding interactions of niclosamide with serum proteins

A study of the binding of niclosamide (NC) to serum proteins such as human serum albumin, hemoglobin, and globulin was carried out using fluorescence and UV-visible spectroscopy. Interactions between NC and these proteins were estimated by Stern-Volmer and van't Hoff equations. The binding constants and the thermodynamic parameters, ΔH, ΔS, and ΔG at different temperatures were also determined by using these equations. Data showed that NC may exhibit a static quenching mechanism with all proteins. The thermodynamic parameters were calculated. Data showed that van der Waals interactions and hydrogen bonds are the main forces for human serum albumin and hemoglobin. Globulin, however, bound to NC via hydrophobic interaction. The spectral changes of synchronous fluorescence suggested that both the microenvironment of NC and the conformation of the proteins changed in relation to their concentrations during NC's binding.

Investigation on the interaction of pyrene with bovine serum albumin using spectroscopic methods

This paper was designed to investigate the interaction of pyrene with bovine serum albumin (BSA) under physiological condition by spectroscopic methods. Spectroscopic analysis of the emission quenching revealed that the quenching mechanism of BSA by pyrene was static. The binding sites and constants of pyrene-BSA complex were observed to be 1.20 and 2.63×10(6) L mol(-1) at 298 K, respectively. The enthalpy change (ΔH) and entropy change (ΔS) revealed that van der Waals forces and hydrogen bonds stabilized the pyrene-BSA complex. Energy transfer from tryptophan to pyrene occurred by a FRET (fluorescence resonance energy transfer) mechanism, and the distance (r=2.72 nm) had been determined. The results of synchronous, three-dimensional fluorescence, and circular dichroism spectra showed that the pyrene induced conformational changes of BSA.

Estimation of Excited State Dipolemoments from Solvatochromic Shifts-Effect of pH

Multicomponent, highly efficient, catalytic synthesis of some polysubstituted imidazole under solvent-free condition is reported. Characterization of polysubstituted imidazole have been carried out by X-ray diffraction (XRD) and spectral techniques. Electronic spectral studies reveal that their solvatochromic behavior depends not only on the polarity of the medium but also on the hydrogen bonding properties of the solvents. Specific hydrogen bonding interaction in polar solvents modulated the order of the two close lying lowest singlet states. The solvent effect on both the absorption and emission spectral results have been analyzed by multiple parametric regression analysis. Solvatochromic effects on the emission spectral position indicate the charge transfer (CT) character of the emitting singlet states both in a polar and a non polar environment. The fluorescence decays for the imidazole fit satisfactorily to a single exponential kinetics. The prototropic studies of N,N-dimethyl-4-(1,4,5-triphenyl-1H-imidazol-2-yl)naphthalen-1-amine (DTINA) reveal that two monocations [imidazole nitrogen protanated (MC1) and dimethylamino nitrogen protanated (MC2)] and a dication [both imidazole nitrogen and dimethylamino nitrogen protanated (DC)] are formed by protonation in both ground and excited states. These observations are in consistent with quantum chemical calculations.

Study on the interaction characteristics of dexamethasone sodium phosphate with bovine serum albumin by spectroscopic technique

The interaction of dexamethasone sodium phosphate (DEX-P) with bovine serum albumin (BSA) was studied by fluorescence quenching in combination with UV-Vis spectroscopic method under near physiological conditions.

Optical properties of 1-(4,5-diphenyl-1-p-tolyl-1H-imidazol-2-yl)naphthalen-2-ol--ESIPT process

This article presents optical, electrochemical, and thermal properties of novel class of green fluorescent 1-(4,5-diphenyl-1-p-tolyl-1H-imidazol-2-yl)naphthalen-2-ol. Detailed photo physical and quantum chemical studies have been performed to elucidate the excited state intramolecular proton transfer (ESIPT) reaction leading a large stokes shifted fluorescence emission from the phototautomer. The results of quantum chemical investigations confirmed the intramolecular charge transfer characteristics of the ESIPT tautomers. The high photoluminescence quantum yield is ascribed to twisted chromophores due to phenyl substituents at 1,2-position of the imidazole ring which restricted intramolecular motion, leading to an optically allowed lowest optical transition without self quenching.

Interaction of fluorescent sensor with superparamagnetic iron oxide nanoparticles

To sense superparamagnetic iron oxides (Fe2O3 and Fe3O4) nanocrystals a sensitive bioactive phenanthroimidazole based fluorescent molecule, 2-(4-fluorophenyl)-1-phenyl-1H-phenanthro [9,10-d] imidazole has been designed and synthesized. Electronic spectral studies show that phenanthroimidazole is bound to the surface of iron oxide semiconductors. Fluorescent enhancement has been explained on the basis of photo-induced electron transfer (PET) mechanism and apparent binding constants have been deduced. Binding of phenanthroimidazole with iron oxide nanoparticles lowers the HOMO and LUMO energy levels of phenanthroimidazole molecule. Chemical affinity between the nitrogen atom of the phenanthroimidazole and Fe(2+) and Fe(3+) ions on the surface of the nano-oxide may result in strong binding of the phenanthroimidazole derivative with the nanoparticles. The electron injection from the photoexcited phenanthroimidazole to the iron oxides conduction band explains the enhanced fluorescence.

Discovery of a new class of natural product-inspired quinazolinone hybrid as potent antileishmanial agents

The high potential of quinazolinone containing natural products and their derivatives in medicinal chemistry led us to discover four novel series of 53 compounds of quinazolinone based on the concept of molecular hybridization. Most of the synthesized analogues exhibited potent leishmanicidal activity against intracellular amastigotes (IC50 from 0.65 ± 0.2 to 7.76 ± 2.1 μM) as compared to miltefosine (IC50 = 8.4 ± 2.1 μM) and nontoxic toward the J-774A.1 cell line and Vero cells. Moreover, activation of Th1 type and suppression of Th2 type immune responses and induction in nitric oxide generation proved that 8a and 8g induce murine macrophages to prevent survival of parasites. Compounds 8a and 8g exhibited significant in vivo inhibition of parasite 73.15 ± 12.69% and 80.93 ± 10.50% against Leishmania donovani /hamster model. Our results indicate that compounds 8a, 8g, and 9f represent a new structural lead for this serious and neglected disease.