Exploration of spectroscopic, computational, fluorescence turn-off mechanism, molecular docking and in silico studies of pyridine derivative.

The present work reports pyridine-based chalones using spectroscopic techniques to use pyridine derivative analysis. The solvatochromic behavior of 3DPP in non-polar, polar protic and aprotic solvents has been investigated experimentally. The photophysical property of the compound in diverse solvents is attributed to the intra-molecular charge transfer interactions. The dipole moment of 3DPP is estimated theoretically and experimentally using various solvatochromic methods. It is observed that there is a bathochromic shift in the emission spectra of 3DPP, which confirms the π → π* transition. Fluorescence quenching of 3DPP is studied. The type of fluorescence quenching mechanism is found to be collisional quenching. A study of FRET theory on 3DPP was carried out with metal ions. There is a considerable energy transfer between 3DPP and metal ions. NLO behaviors of the compound have been revealed with the help of Kurtz-Perry powder technique. Additionally, the title molecule is docked, carried ADMET studies and drug-like activity using in silico tools. It is probed for antifungal activity through bioinformatics kit which showed potential information.

Effect of fluorescence quenching model on quinoline derivative with cobalt chloride metal ion using steady state and time resolved spectroscopic methods.

Quinoline derivative, i.e. quinilone yellow with the scientific name [sodium 2-(2,3-dihydro-1,3-dioxo-1H-inden-2-yl)quinoline-6,8-disulphonate] (SQDS) is analysed for fluorescence resonance energy transfer (FRET). Fluorescence quenching mechanism is studied by employing steady state and transient state spectroscopic measurements. Cobalt chloride is used as quencher in the present study. Linearity was observed in Stern-Volmer plots for transient state as well as steady state. This was further attributed to a mechanism of collisional quenching. Efficiency in fluorescence quenching is observed as there is a correlation between quenching constants of both transient and steady state. A significant energy transfer is reported between metal ions and SQDS molecule, according to FRET theory. Characterization results are studied and analysed. Application in the field of non-linear optics are predicted for SQDS. With Kurtz and Perry powder technique, SHG (second harmonic generation) efficiency was measured using Q-switched mode locked Nd:YAG laser emitting 1064 nm the first time with this compound.

Analysis of Fluorescence Quenching of Coumarin Derivative under Steady State and Transient State Methods.

Nature has gifted us many organic molecules which have remarkable influence in our daily life. Amongst many organic molecules, heterocyclic organic molecules have gained potential applications in the advanced field of biomedicine, pharmaceutical, electronics and many more. In the present work fluorescence quenching of biologically active fluorescent probe 8EMOHCC by aniline in different solvents have been studied at room temperature. To understand the molecular behaviour in different media, solvents of different refractive index and dielectric constant have been used. Spectroscopic measurement techniques such as UV/Vis spectroscopy and time related single photon counting are employed to characterise the molecule at room temperature. The fluorescence quenching study shows linear dependence of SV-plot in solvents of different dielectric constants. It reveals that quenching reactions are dynamic in nature. Various parameters of quenching have been determined and identified the type of quenching involved in the quenching reaction. Further, kq is found to be greater than [Formula: see text] in ACN, methanol, propanol and dioxane. Activation energy of quenching (Ea) is found to be greater than energy of diffusion (Ed) in ACN, methanol, propanol, THF solvents and Ed > Ea in dioxane, indicating that quenching reaction is not solely controlled by material diffusion but also activation process.

Investigation of interaction between boronic acids and sugar: effect of structural change of sugars on binding affinity using steady state and time resolved fluorescence spectroscopy and molecular docking.

Binding interactions of boronic acid derivatives viz. 2-Methylphenylboronic acid (B1) and 3-Methoxyphenylboronic acid (B2) with mono saccharides (arabinose, fructose and galactose) and disaccharides (sucrose, lactose and maltose) in aqueous condition at pH 7.4 by means of fluorescence spectroscopy is reported in the present investigation. Sugar sensing as well as continuous glucose monitoring (CGM) plays a significant role in diabetes regulation. Sugar sensors mediated through enzymes have their own drawbacks, which led to encouragement to search for designing new sensors through alternate approaches. Among many, fluorescence-based sensors are drawing more attention. Boronic acid-based fluorescence sensors have the capacity to bind reversibly with diols, which makes their demand high in applications. Addition of sugar reduces fluorescence intensities. Change in intensities is associated to cleavage of intermolecular hydrogen bonding which leads in reduced stability of boronate ester. Lineweaver-Burk and Benesi-Hildebrand equation is used for analysing data. Mono sugars are estimated to have higher binding constants. Mutarotation leads to structural changes in saccharides which play a key role in binding interactions. Sugars in furanose form are found to be highly favoured for binding. Molecular docking of B1 and B2 with proteins with PDB ID: 2IPL and 2IPM being periplasmic was done with the help of Schrodinger Maestro 11.2 version. GLIDE scores terms are used for expressing binding affinity.

Preparation and optical parameter characterization of two aldehyde derivative thin films for photonic applications by drop casting method.

In this study, thin films of polymer poly(methyl methacrylate) were prepared using a drop casting method. Two newly synthesized aldehyde derivatives, 2-bromomalonaldehyde and 5,6-dihydroimidazo[2,1-b]thiazole-2-carbaldehyde, were used at different concentrations to dope the films. The prepared films were transparent and therefore studied for application in photonics. Optical characterization of the samples was carried out using different spectroscopy techniques. Absorption spectra for both samples were obtained using a UV-vis light spectrophotometer. Other significant optical parameters, such as refractive index, extinction coefficient, and band gap energies, were calculated from the absorption spectra. The effect of doping concentration on these parameters was studied. Emission spectra were obtained using a fluorescence spectrophotometer and the effect of doping was observed. Fourier transform infrared spectra of the doped films were obtained and compared with the pure compound to note changes in peak values and peak intensity. This present work studied the effect of doping on optical properties and examined the application of the samples for photonics.

Photoluminescence, TGA/DSC and photocatalytic activity studies of Dy3+ doped SrY2O4 nanophosphors.

Dy3+:SrY2O4 nanophosphors were prepared via a solution combustion method using glycine as an organic fuel. The structural, optical, and thermal properties of the nanophosphors were studied. Strain and crystal size were calculated via W-H analysis. The direct energy band gap is nearly 4.9 eV and photocatalytic studies reveal that Rh-B degradation of almost 50% can be achieved.

Bimolecular fluorescence quenching reactions of the biologically active coumarin composite 2-acetyl-3H-benzo[f]chromen-3-one in different solvents.

A study on fluorescence quenching was carried out for the coumarin derivative 2-acetyl-3H-benzo[f]chromen-3-one (2AHBC) with aniline at room temperature. Efficient fluorescence quenching was observed and Stern-Volmer (S-V) plots showed upward curves from linearity in all solvents of different polarities. For the solute 2AHBC, ground state complex formation does not hold in our study. The kinetic distance (r) value was found to be greater than the encounter distance (R) and indicated that the quenching reaction was held within the sphere of action. Diffusion-limited reactions were found to be more prominent in high polarity solvents, namely dimethyl sulfoxide (DMSO), DMF, ACN, methanol, ethanol, propanol and DCM. The relationships between quenching constant (KSV ) and dielectric constants (ε) of the different solvents were studied.

Specific interactions of alcohols and non-alcohols with a biologically active boronic acid derivative: a spectroscopic study.

The photophysical properties of 4-fluoro-2-methoxyphenyl boronic acid (4FMPBA) are characterized using absorption and fluorescence techniques in series of non-alcohols and alcohols. The results are analyzed using different solvent polarity functions and Kamlet and Catalan's multiple regression approaches. The excited state dipole moment and change in dipole moment are calculated using both the solvatochromic shift method and Reichardt's microscopic solvent polarity parameter ETN. The ground state dipole moment is evaluated using quantum chemical calculations. It is found that general solute-solvent and hydrogen bond interactions are operative in this system. A red shift of ~ 9 nm in the emission spectra is observed with an increase in the solvent polarity, which depicts π→π(*) transitions, as well as the possibility of an intramolecular charge transfer (ICT) character in the emitting singlet state of 4FMPBA. The relative quantum yield, radiative and non-radiative decay constants are calculated in alkanes and alcohols using the single point method. It is found that the quantum yield of the molecule varies from 16.81% to 50.79% with the change in solvent polarity, indicating the dependence of fluorescence on the solvent environment. Copyright © 2015 John Wiley & Sons, Ltd.

Fluorescence characteristics of aryl boronic acid derivate (PBA).

The absorption and fluorescence spectra of newly synthesized aryl boronic acid derivative namely Phenyl boronic acid (PBA) have been recorded in various solvents of different polarities. The ground state dipole moment of PBA was obtained from quantum chemical calculations. Solvatochromic correlations were used to estimate the ground state (µg) and excited state (µe) dipole moments. The excited state dipole moments are observed to be greater than the ground state dipole moments. Further, the ground and excited state dipole moments are not parallel but subtend by an angle of 70°. The changes in dipole moment (Δµ) were calculated both from solvatochromic shift method and microscopic solvent polarity parameter (ET(N)), and the values are compared. Solvent effects on the absorption and fluorescence spectra were quantified using Reichardt's and bulk solvent polarity parameters were complemented by the results of the Kamlet-Taft treatment.

Solvent effect on the relative quantum yield and fluorescence quenching of a newly synthesized coumarin derivative.

We estimated the relative florescence quantum yield (Φ) of 8-methoxy-3-[1-(4,5-dicarbomethoxy-1,2,3-triazoloacetyl)]coumarin [8MDTC] using a single-point method with quinine sulfate in 0.1 M of sulfuric acid used as a standard reference. The fluorescence lifetimes, radiative and non-radiative decay rate constants are calculated. Relative quantum yields were found to be less in the non-polar solvents, indicating that the solute exhibits less fluorescence in a non-polar environment. The fluorescence quenching of [8MDTC] by aniline was studied at room temperature by examining the steady state in five different solvents in order to explore various possible quenching mechanisms. The experimental results show a positive deviation in Stern-Volmer plots in all solvents. Ground state complex and sphere of action static quenching models were used to interpret the results. Many quenching rate parameters were calculated using these models. The values of these parameters suggest that the sphere of action static quenching model agrees well with the experimental results. Further, a finite sink approximation model was used to check whether these bimolecular reactions were diffusion limited or not. The values of the distance parameter R' and the diffusion coefficient D were determined and are compared with the values of the encounter distance R and diffusion coefficient D calculated using the Stokes-Einstein equation.

"Estimation of ground and excited state dipole moments of aryl boronic acid derivative by solvatochromic shift method".

In the present work, the absorption and fluorescence spectra of newly synthesized aryl boronic acid derivative namely 2-Methylphenyl boronic acid (2MPBA) have been recorded in various solvents of different polarities. The ground state dipole moment of 2MPBA was obtained from quantum chemical calculations. Solvatochromic correlations were used to estimate the ground state (µ g ) and excited state (µ e ) dipole moments. The excited state dipole moments are observed to be greater than the ground state dipole moment and ground and excited state dipole moments are not parallel but subtend by an angle of 88(0). Further, the changes in dipole moment (Δµ) were calculated both from solvatochromic shift method and microscopic solvent polarity parameter (E T (N) ), and the value are compared. The spectral variations were analyzed by Kamlet-Taft parameters.

Solvent effect on the relative quantum yield and fluorescence quenching of 2DAM.

The relative quantum yield of diethyl 2-acetamido-2-((3-oxo-3H-benzo[f]chromen-1-yl)methyl)malonate [2DAM] is estimated using single point method with quinine sulfate as standard reference. The quantum yield varies between 0.1161 and 0.3181 depending on the nature of the solvent. The rates of radiative and non radiative decay constants are also calculated. The fluorescence quenching of [2DAM] by aniline is studied at room temperature, by steady state, in five different solvents namely acetonitrile (AN), 1,4 dioxane (DX), 1,2 dichloroethane (DCE), tetrahydrofuran (THF) and toluene (TOL), in order to explore various possible quenching mechanisms. The experimental results show a positive deviation in Stern Volmer plots for all solvents. Various parameters for the quenching process are determined by ground state complex, sphere of action static quenching model and finite sink approximation model. The magnitudes of these rate parameters indicate that positive deviation in the Stern Volmer (SV) plot is due to both static and dynamic processes. Further, finite sink approximation model is used to check whether these bimolecular reactions were diffusion limited or not. The values of distance parameter R' and diffusion co efficient D are determined and then compared with the values of encounter distance R and diffusion coefficient D calculated using Stokes-Einstein equation.

Static and dynamic model fluorescence quenching of laser dye by carbon tetrachloride in binary mixtures.

The fluorescence quenching of laser dye namely 4,4(‴)-Bis (2-butyloctyl-oxy)-p-quaterphenyl [BIBUQ] by carbon tetrachloride has been studied in different solvent mixtures of 1-4 dioxane (DN) and acetonitrile (AN) at room temperature. The quenching is found to be appreciable and a positive deviation from linearity was observed in the Stern-Volmer plot in all the solvent mixtures. Various parameters for the quenching process have been determined by sphere of action static quenching model and finite sink approximation model. The magnitudes of these rate parameters indicate that positive deviation in the Stern-Volmer (S-V) plot is both due to static and dynamic processes.

Can combination metronomic therapy overcome chemoresistance in cholangiocarcinoma? A literature review.

Cholangiocarcinoma (CCa) is relatively resistant to chemotherapy as well as radiation therapy, and complete resection is the main curative therapy for these patients. The prognosis for patients with unresectable intrahepatic CCa (iCCa) is extremely poor. A 55-year-old woman presented at our hospital with abdominal pain. After evaluation, she was diagnosed to have multifocal iCCa. She did not opt for standard chemotherapy and therefore received oral metronomic therapy with a combination of celecoxib, etoposide, and cyclophosphamide for a total of 30 months. Presently, she is 57 months post diagnosis and 27 months post cessation of all treatment and continues to be in complete radiological remission. In the present report, we review the literature and discuss whether metronomic scheduling of biologic agents and anticancer drugs will be able to overcome chemoresistance and improve the outcome in cholangiocarcinoma. References for the review were identified through searches of Pubmed for the last 10 years as well as searches of the files of the authors themselves. The final list was generated on the basis of originality and relevance to this review.

Protective effect of nebivolol on reserpine-induced neurobehavioral and biochemical alterations in rats.

Reserpine-induced orofacial dyskinesia is a model that shares some mechanists' aspects with tardive dyskinesia whose pathophysiology has been related to oxidative stress. The present study was aimed to explore neuroprotective effects of nebivolol, an antihypertensive agent, on reserpine-induced neurobehavioral and biochemical alterations in rats. Reserpine (1mg/kg, s.c.) was used to induce neurotoxicity. Administration of reserpine for 3 days every other day significantly increased the vacuous chewing movements (VCMs), tongue protrusions (TPs) and reduced the locomotor activity in rats. Pre-treatment with nebivolol (5 and 10mg/kg, p.o. for 5 days) showed dose dependant decrease in VCMs and TP induced by reserpine. Nebivolol also showed significant improvement in locomotor activity. Reserpine significantly increased lipid peroxidation and reduced the levels of defensive antioxidant enzymes like catalase (CAT), superoxide dismutase (SOD) and reduced glutathione (GSH) in rat brain. Nebivolol reversed these effects of reserpine on oxidative stress indices; indicating amelioration of oxidative stress in rat brains. The results of the present study indicated that nebivolol has a protective role against reserpine-induced orofacial dyskinesia. Thus, the use of nebivolol as a therapeutic agent for the treatment of tardive dyskinesia may be considered.

Fluorescence quenching of biologically active carboxamide by aniline and carbon tetrachloride in different solvents using Stern-Volmer plots.

Fluorescence quenching of biologically active carboxamide namely (E)-2-(4-chlorobenzylideneamino)-N-(2-chlorophenyl)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide [ECNCTTC] by aniline and carbon tetrachloride (CCl4) quenchers in different solvents using steady state method and time resolved method using only one solvent has been carried out at room temperature to understand the role of quenching mechanisms. The Stern-Volmer plot has been found to be linear for all the solvents studied. The probability of quenching per encounter p (p') was determined in all the solvents and was found to be less than unity. Further, from the studies of rate parameters and life time measurements in n-heptane and cyclohexane with aniline and carbon tetrachloride as quenchers have been shown that, the phenomenon of quenching is generally governed by the well-known Stern-Volmer (S-V) plot. The activation energy Ea (or E'a) of quenching was determined using the literature values of activation energy of diffusion Ed and the experimentally determined values of p (or p'). It has been found that, the activation energy Ea (E'a) is greater than the activation energy for diffusion Ed in all solvents. Hence, from the magnitudes of Ea (or E'a) as well as p (or p') infer that, the quenching mechanism is not solely due to the material diffusion, but there is also contribution from the activation energy.

Solvent effect on absorption and fluorescence spectra of three biologically active carboxamides (C1, C2 and C3). Estimation of ground and excited state dipole moment from solvatochromic method using solvent polarity parameters.

The absorption and fluorescence spectra of three Carboxamides namely (E)-2-(4-Chlorobenzylideneamino)-N-(2-chlorophenyl)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (C(1)), (E)-N-(3-Chlorophenyl)-2-(3, 4-dimethoxybenzylideneamino)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (C(2)) and (E)-N-(3-Chlorophenyl)-2-(3,4,5-trimethoxybenzylideneamino)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (C(3)) have been recorded at room temperature in solvents of different polarities using dielectric constant (ε) and refractive index (n). Experimental ground (µ(g)) and excited (µ(e)) state dipole moments are estimated by means of solvatochromic shift method and also the excited dipole moments are estimated in combination with ground state dipole moments. It was estimated that dipole moments of the excited state were higher than those of the ground state of all three molecules. Further, the changes in dipole moment (Δµ) were calculated both from solvatochromic shift method and on the basis of microscopic empirical solvent polarity parameter (E(N)(T)) and the values are compared.