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ABSTRACT: A novel, simple but highly selective fluorescent probe is developed for the direct detection of sulfide ions [S(2-)] based on the fluorescence quenching of the functionalized CdS QDs in aqueous solution at trace levels and successfully applied for quantitation of S(2-) from water samples in a complex matrix pretreatment exclusive of pretreatment by a standard addition method.
The Analyst 01/2013; · 4.23 Impact Factor
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ABSTRACT: In the present study, fluorescence spectroscopy in combination with UV–vis absorption spectroscopy and synchronous fluorescence spectroscopy (SFS) was employed to investigate the binding affinity of pyrimidine derivative, 2-amino-6-hydroxy-4-(3,4-dimethoxyphenyl)-pyrimidine-5-carbonitrile (AHDMPPC) to human serum albumin (HSA) under the physiological conditions. In the mechanism discussion, it was proved that the fluorescence quenching of HSA by AHDMPPC is a result of the formation of AHDMPPC–HSA complex. The quenching mechanism and number of binding sites (n ≈ 1) were obtained by fluorescence titration data. Binding parameters calculated from Stern–Volmer method showed that the AHDMPPC bind to HSA with the binding affinities of the order 104 L mol–1. The thermodynamic parameters studies revealed that the binding was characterized by negative enthalpy and positive entropy changes −13.06 kJ/mol and 51.34 J/mol K–1 (from the Van’t Hoff equation) and suggest that the binding reaction was exothermic and hydrophobic interaction is the predominant intermolecular forces stabilizing the complex. The specific binding distance (r = 2.25 nm) between donor HSA and acceptor AHDMPPC was obtained according to fluorescence resonance energy transfer (FRET). Furthermore, the synchronous spectral result, three–dimensional fluorescence spectra and circular dichroism (CD) indicates that the secondary structure of HSA was changed in the presence of AHDMPPC.
Industrial & Engineering Chemistry Research 12/2012; 51(1):95–102. · 2.24 Impact Factor
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ABSTRACT: In the present study, fluorescence spectroscopy in combination with UV–vis absorption spectroscopy and synchronous fluorescence spectroscopy (SFS) was employed to investigate the binding affinity of pyrimidine derivative, 2-amino-6-hydroxy-4-(3,4-dimethoxyphenyl)-pyrimidine-5-carbonitrile (AHDMPPC) to human serum albumin (HSA) under the physiological conditions. In the mechanism discussion, it was proved that the fluorescence quenching of HSA by AHDMPPC is a result of the formation of AHDMPPC–HSA complex. The quenching mechanism and number of binding sites (n ≈ 1) were obtained by fluorescence titration data. Binding parameters calculated from Stern–Volmer method showed that the AHDMPPC bind to HSA with the binding affinities of the order 104 L mol–1. The thermodynamic parameters studies revealed that the binding was characterized by negative enthalpy and positive entropy changes −13.06 kJ/mol and 51.34 J/mol K–1 (from the Van’t Hoff equation) and suggest that the binding reaction was exothermic and hydrophobic interaction is the predominant intermolecular forces stabilizing the complex. The specific binding distance (r = 2.25 nm) between donor HSA and acceptor AHDMPPC was obtained according to fluorescence resonance energy transfer (FRET). Furthermore, the synchronous spectral result, three–dimensional fluorescence spectra and circular dichroism (CD) indicates that the secondary structure of HSA was changed in the presence of AHDMPPC.
Industrial & Engineering Chemistry Research 12/2012; 51(1-DOI: 10.1021/ie202005c):95–102. · 2.24 Impact Factor
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ABSTRACT: Steady state fluorescence and UV–vis absorption spectroscopic techniques have been exploited to explore
the binding interaction of a antibacterial pyrimidine derivative 2-amino-6-hydroxy-4-(4-hydroxyphenyl)-
pyrimidine-5-carbonitrile (AHHPPC) with the model transporter protein, human serum albumin
(HSA) under the physiological conditions. It exhibits antibacterial activity against Escherichia coli and
Staphylococcus aureus. Analysis of fluorescence quenching data of HSA at different temperatures using
Stern–Volmer methods revealed the formation of AHHPPC–HSA complex with binding affinities of the
order 104 M�1. The binding site number (n � 1) and corresponding thermodynamic parameters (DG),
(DH) and (DS) were calculated, indicated that binding reaction was endothermic and the hydrophobic
interactions plays a major role in stabilizing the complex. The binding distance (r = 3.13 nm) between
donor (HSA) and acceptor (AHHPPC) was obtained according to FRET. Changes in the albumin secondary
structure imparted by the compound was confirmed using synchronous fluorescence, electronic absorption,
circular dichroism (CD) and three-dimensional (3D) fluorescence spectroscopy. All these experimental
results clarified that AHHPPC could bind to HSA and be effectively transported and eliminated in body,
which could be a useful guideline for further drug design.
Journal of Photochemistry and Photobiology B Biology 10/2012; 118:1-8. · 2.81 Impact Factor
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ABSTRACT: The molecular interactions between salicylic acid (SA) and proflavin hemisulfate (PF) were investigated using fluorescence and UV-VIS absorption spectroscopy in an aqueous micellar environment. Changes in the absorption spectra of SA in the presence of PF indicate a ground state interaction between salicylate and proflavine hemisulfate ions to form a complex. The excitation bands of SA monitored at its emission wavelength reveal a red spectral shift of 8390.54 and 2037.75 cm(-1) when compared with absorption bands. The intensity of both excitation bands decreased in the presence of increasing amounts of PF. The absence of excitation bands of PF rules out the possibility of its direct excitation and suggests energy transfer from excited SA to PF, resulting in quenching of the SA fluorescence. The fluorescence quenching results were found to fit the well-known Stern-Volmer (S-V) relation. S-V plots at different temperatures were used to further evaluate thermodynamic parameters such as ∆G, ∆H and ΔS. The thermodynamic and kinetic data obtained from the quenching results were used to investigate the possible mechanism of binding, the nature of the binding force and the distance between SA and PF molecules. The linear relation between SA fluorescence quenching and PF concentration used to develop an analytical method for the determination of PF from Lorexane (a veterinary cream) using a fluorescence quenching method. Copyright © 2012 John Wiley & Sons, Ltd.
Luminescence 10/2012; · 1.73 Impact Factor
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ABSTRACT: Current study employs fluorescence spectroscopy, UV–Vis absorbance spectroscopy, dynamic light scattering (DLS) and cyclic voltammetry (CV) to investigate the interaction of safranine dye with spherical
shaped silver nanoparticles (AgNPs) coated with trisodium citrate. In fluorescence spectroscopic study
we used the AgNPs and safranine dye as component molecules for the construction of FRET, whereas
AgNPs serve as donor fluorophore and safranine as acceptor. The fluorescence quenching of AgNPs followed by sensitization of safranine occurs almost simultaneously by addition of safranine dye with different concentrations, indicating fluorescence energy transfer observed between them. Interaction
between safranine and AgNPs is also confirmed by using UV–Vis absorption spectroscopy. Addition of safranine results in the significant decrease in the absorbance of AgNPs at 423 nm and simultaneous
increase in the absorbance of safranine at 518, 276 and 248 nm which is indication of rapid binding of
safranine molecules with AgNPs. However CV measurements reveals that the safranine molecule does
not alter the redox properties of the AgNPs but the safranine molecule lose their redox properties upon
getting bonded with AgNPs. This clearly confirms that the safranine molecules get attached on the surface
of AgNPs which was also supported by the DLS as well as zeta potential measurement.
Journal of Photochemistry and Photobiology B Biology 05/2012; 113(http://dx.doi.org/10.1016/j.jphotobiol.2012.05.006):63-69. · 2.81 Impact Factor
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ABSTRACT: Current study employs fluorescence spectroscopy, UV-Vis absorbance spectroscopy, dynamic light scattering (DLS) and cyclic voltammetry (CV) to investigate the interaction of safranine dye with spherical shaped silver nanoparticles (AgNPs) coated with trisodium citrate. In fluorescence spectroscopic study we used the AgNPs and safranine dye as component molecules for the construction of FRET, whereas AgNPs serve as donor fluorophore and safranine as acceptor. The fluorescence quenching of AgNPs followed by sensitization of safranine occurs almost simultaneously by addition of safranine dye with different concentrations, indicating fluorescence energy transfer observed between them. Interaction between safranine and AgNPs is also confirmed by using UV-Vis absorption spectroscopy. Addition of safranine results in the significant decrease in the absorbance of AgNPs at 423 nm and simultaneous increase in the absorbance of safranine at 518, 276 and 248 nm which is indication of rapid binding of safranine molecules with AgNPs. However CV measurements reveals that the safranine molecule does not alter the redox properties of the AgNPs but the safranine molecule lose their redox properties upon getting bonded with AgNPs. This clearly confirms that the safranine molecules get attached on the surface of AgNPs which was also supported by the DLS as well as zeta potential measurement.
Journal of photochemistry and photobiology. B, Biology 05/2012; 113:63-9. · 1.87 Impact Factor
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ABSTRACT: The binding of riboflavin (RBF) to norfloxacin (NF) was investigated by spectroscopic techniques. The results revealed that
RBF caused the fluorescence quenching of NF by complex formation. The binding parameters and corresponding thermodynamic parametersΔH, ΔG and ΔS at different temperatures were calculated. The negative enthalpy(ΔH) and positive entropy(ΔS) values indicated that both hydrogen bond and hydrophobic forces played major roles in the binding of RBF to NF. The distance
r between donor (NF) and acceptor (RBF) was obtained according to the Forster’s theory of non-radiative energy transfer. The
method of quenching was successfully applied for the determination of riboflavin from pharmaceutical samples.
Journal of Solution Chemistry 04/2012; 39(1):97-106. · 1.41 Impact Factor
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ABSTRACT: A fluorimetric method based on fluorescence enhancement effect was developed for the determination of adenosine 5'-monophosphate (AMP) with 9-anthracene carboxylic acid (9-ANCA)-cetyl trimethyl ammonium bromide (CTAB) system. Fluorescence intensity of 9-ANCA was decreased by the addition of CTAB but addition of AMP again rose the intensity of 9-ANCA gradually. The observed fluorescence enhancement is attributed to the competitive binding reaction of 9-ANCA and adenosine to CTAB. The enhancement in the fluorescence intensity was found proportional to the concentration of AMP over the range 2.0 × 10(-4) to 1.2 × 10(-3) mol dm(-3). The ion pair complex is formed spontaneously between 9-ANCA and CTAB. Since the binding interaction is larger for the adenosine-CTAB pair, the fluorophore 9-ANCA will be released. The quantum yield of free 9-ANCA is higher therefore its fluorescence observed at 417 nm wavelength is enhanced. This mechanism of competitive molecular interaction is further confirmed by conductometric measurements. The method was applied successfully for the determination of AMP from pharmaceutical sample. The method is more selective, sensitive and relatively free from interferences.
Journal of Fluorescence 06/2011; 21(5):1997-2003. · 2.11 Impact Factor
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ABSTRACT: Benzoxazine, Benzothiazines have been synthesized in excellent yields at ambient temperature by
PEG -400 mediated protocol under solvent free conditions. The enviourment freely protocol with
excellent yields are the interesting features of the present method. All the synthesized compounds
have been tested for their anti-bacterial and anti-fungal activity.
Scholars Research Library Der Pharma Chemica. 03/2011;
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ABSTRACT: The interaction between Norfloxacin (NF) and Proflavine hemisulphate (PF) was investigated by spectroscopic tools like UV-VIS absorption and Fluorescence spectroscopy. It was proved that fluorescence quenching of NF by PF is due to the formation of NF-PF complex which was supported by UV-VIS absorption study. The study of thermodynamic parameters suggested that the key interacting forces are hydrogen bond and van der Waal's interactions and the binding interaction was spontaneous. The distance r between NF and PF was obtained according to the Förster's theory of non-radiative energy transfer. The fluorescence quenching mechanism was applied to estimate PF directly from pharmaceutical samples.
Journal of Fluorescence 03/2011; 21(4):1789-96. · 2.11 Impact Factor
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ABSTRACT: The silica sulfuric acid (SSA) serves as mild, efficient and reusable catalyst for the synthesis of aryl benzothiazole in one pot conversion with excellent yield. The reusability, excellent yields with easy work up make it an interesting alternative for the synthesis of aryl benzothiazole.
Der Pharma Chemica. 01/2011; 3:189-193.
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ABSTRACT: A simple, sensitive, and selective stability indicating high performance liquid chromatographic method has been developed and validated for quantitative analysis of carprofen (CPF) in presence of its degradation products. All degradation products in acid hydrolysis and photolysis were separated, identified by mass spectroscopic method and probable structures were elucidated. The forced degradation studies were performed on a bulk sample of CPF by using various methods like 0.1 M hydrochloric acid, 0.1 M sodium hydroxide, 0.33% hydrogen peroxide (H(2)O), heating at 60°C and exposure to UV light at 254 nm. A 5 μm particle octa desyl silane (ODS) column (150 mm × 4.6 mm) was used with acetonitrile-ammonium acetate (100 mM, pH-6.7) 40:60 (v/v) as a mobile phase at flow rate of 1.2 mL/min. Column oven temperature was maintained at 30°C and quantitation was achieved at 239 nm on the basis of peak area. The linear range and correlation coefficient (r(2)) was found 0.5-60 μg/mL and 0.9999 respectively. The limit of detection (LOD) and limit of quantitation (LOQ) were obtained 0.066 μg/mL and 0.20 μg/mL respectively . The proposed method was found to be suitable and accurate for quantitative analysis, stability study and characterisation of degradation product of CPF.
Journal of chromatographic science 01/2011; 49(6):434-8. · 0.88 Impact Factor
