Fluorimetric investigation of supramolecular system by modified β-cyclodextrin and its analytical application

The supramolecular interaction of MAH-β-cyclodextrin (MAH-β-CD, a modified β-cyclodextrin carrying seven vinyl carboxylic acid groups) and meferamic acid (MF) has been studied by spectrofluorimetry. The results showed that MAH-β-CD reacted with MF to form a host-guest complex (MAH-β-CD-MF) with stoichiometry (1:1) and the inclusion constant (K=7.15×10(2) L/mol) was ascertained by the typical double reciprocal plots. From the phase-solubility diagram, an increase in the water solubility of the drug was observed and the apparent stability constant (K(1:1)) was calculated to be 8.62×10(2) L/mol. Furthermore, the thermodynamic parameters (ΔG°, ΔH° and ΔS°) of MAH-β-CD-MF were obtained and the inclusion mechanism was also preliminarily discussed. In order to further confirm the experimental results, investigation on the molecular modeling was performed. On the basis of the significant enhancement of the fluorescence intensity of MF, a spectrofluorimetric method for MF determination in bulk aqueous solution in the presence of MAH-β-CD was developed. The linear range was 2.00×10(-8)-9.00×10(-5) mol/L and the detection limit was 3.36×10(-9) mol/L. The proposed method was successfully applied to determine MF in tablets, serum and urine with the satisfactory result.     

Resonance Rayleigh scattering study of the interaction of bleomycinA_5 with nucleic acids and its analytical application

The interaction of bleomycinA5 with nucleic acids has been investigated by using resonance Rayleigh scattering (RRS), molecular absorption and fluorescence spectra. The result shows that in near pH 2.2 buffer medium and absence of any metal ions, nucleic acids are capable of binding with bleomycinA5 (BLMA5) to form complexes which can remarkably enhance the RRS intensity and result in batho- chromic and hyperchromic molecular absorption of nucleic acids and fluorescence quenching of bleomycinA5. The RRS spectral characteristics for the binding products of bleomycinA5 with various DNA and RNA are similar, and the maximum RRS peaks are at 301 nm for ctDNA and sDNA, 370 nm for hsDNA, 310 nm for RNAtypeVI and RNAtypeIII, respectively. The increments of RRS intensity are greatly different in which DNA enhances greatly and RNA enhances lightly. In this work, the optimum condi- tions of the interaction and some influencing factors have been investigated. The reaction mechanism and a binding model for the interaction of BLMA5 with the nucleic acids are discussed. In addition, a highly sensitive, simple and rapid new method for the determination of DNA has been developed. The detection limits (3σ) are 5.7 ng/mL for ctDNA, 7.4 ng/mL for sDNA and 9.2 ng/mL for hsDNA, respectively. The method can be applied to determination of trace amounts of DNA.     

Study on the resonance Rayleigh scattering spectra and resonance non-linear spectra of congo red-amikacin system and its analytical application

The interaction between congo red (CR) and amikacin (AMK) was studied by resonance Rayleigh scattering (RRS), frequency doubling scattering (FDS) and second-order scattering (SOS) combining with absorption spectrum. In a weak acidic medium, CR combined with AMK to form an ion association complex with the composition ratio of 1∶1 by electrostatic interaction, hydrophobicity and charge transferring effect. As a result, the new spectra of RRS, FDS, and SOS appeared and their intensities were enhanced greatly. The maximum wavelengths of RRS, FDS and SOS were located at 563 nm, 475 nm and 940 nm, and the scattering intensities were proportional to the concentration of AMK. These three methods have very high sensitivities, and the detection limits were 4.0 ng·mL?1 for RRS, 3.6 ng·mL?1 for FDS and 1.9 ng·mL?1 for SOS, respectively. At the same time, the methods have better selectivity. A new method for the determination of trace amounts of AMK with congo red by resonance scattering technique has been developed. The recovery for the determination of AMK in blood serum and urine sample was between 95.5% and 105.5%. In this study, the properties, such as enthalpy of formation, charge distribution and mean polarizability, were calculated by AM1 quantum chemistry method. In addition, the reaction mechanism and the reasons for the enhancement of scattering spectra were discussed.     

Voltammetric studies on the interaction of amikacin with methyl blue and its analytical application

A new method to determine the concentration of amikacin(AMK)using methyl blue(MB)as electrochemical probe was developed in this paper.In pH 4.5 Britton-Robinson(B-R)buffer solution,the MB reacted with AMK to form ion association complexes,which led to the reductive peak current of MB at-0.275 V(versus SCE)to decrease,and the decreases were linear with the concentration of AMK in the range of 1.0-60.0 mg/L,the regression of equation isΔIp(nA)=-8.48 102.36c(mg/L), correlation coefficientγis 0.997.The conditions for determining the concentration of AMK using linear sweep voltammetry(SLV) were optimized.The method was used to determine the content of amikacin commercially available with satisfactory results.     

The effect of γ-ray-irradiated conducting polymer electrolyte and its application of dye-sensitized solar cells to building window glass system

Journal of Solid State Electrochemistry - In the present study, γ-ray-irradiated and un-irradiated PVA/PPy/KI/I2 conducting polymer electrolytes have been prepared for dye-sensitized solar...     

The resonance Rayleigh scattering of the interaction of copper(Ⅱ)-bleomycinA2 with DNA and its analytical application

The forming of bleomycinA2-Cu(Ⅱ) cationic chelate and the interaction of the chelate with DNA have been investigated by using resonance Rayleigh scattering(RRS),molecular absorption and fluorescence spectra.The result shows that in aqueous solution,bleomycinA2(BLMA2) can react with Cu(Ⅱ) to form 1:1 cationic chelate which contributes to the changes of the absorption spectra and the quenched fluorescence of BLMA2.When the cationic chelate further bound with DNA to form ternary ion-association complexes,the r...     

The cavity size effect on the fluorescence properties of 4′-dimethylaminoacetophenone complexed with cyclodextrins

Fluorescence properties of excited 4^′-dimethylaminoacetophenone (DMAAP) complexed with α-, β-, and γ-cyclodextrins (CDs) were studied by means of steady state and time-resolved laser spectroscopy. The 1:2 DMAAP–α-CD and 1:1 DMAAP–β-CD complexes exhibited dual fluorescence in neutral aqueous solutions while only the fluorescence from the locally excited state was observed in the case of DMAAP complexed with γ-CD. The CD cavity size effect on the excited state dynamics of DMAAP–CD complexes was further discussed. It revealed that polarity effect introduced by the hydrophobic cavity is more important in controlling of the photochemistry of DMAAP than the restriction of molecular motion inside the CD cavity.     

Conia-ene annulation of the α-cyano β-TMS-capped alkynyl cycloalkanone system and its synthetic application

Under catalysis with ZnI(2), an effective annulation process of ω-silylacetylenic α-cyano ketones, leading to the formation of various bicyclic frameworks characterized with a TMS-containing methylenecyclopentane ring, has been developed.     

Fluorescence enhancement effect and the interaction between donor and acceptor

A new theoretical equation for fluorescence enhancement effect between donor and acceptor has been introduced.By using it we determined the binding constants and numbers of binding sites of five medicines,including chlorogenic acid,forsythiaside norfloxacin,Ciprofloxacin and fluorenone,to γ-globulin.     

The structure of 6,6′-biquinolyl and its dication in solution

Conformational analysis of 6,6-biquinolyl and its dication was performed using dipole moments and data from electric and magnetic birefringence. The rotation angles between the quinoline rings for thecis- andtrans-conformers in solution are 50°. The emergence of positive charges on both heteroaromatic rings does not result in noticeable changes in the spatial structure.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 330–332, February, 1994.     

Study on β-cyclodextrin inclusion of Zn(II) aromatic complex and its analytical application

A new β-cyclodextrin (β-CD) inclusion compound Zn(2H1NA)₂·2β-CD (2H1NA = 2-hydroxy-1-naphthoic acid) was prepared. The structure was characterized by ¹H NMR, IR, the fluorescence spectra, thermogravimetric analysis (TG–DTA) and elementary analysis. Meanwhile, the mechanism of the formation of the supramolecular system (2H1NA:Zn(II):β-CD) was studied and discussed by spectrofluorimetry. The results showed that the naphthalene rings of the Zn(II) aromatic complex Zn(2H1NA)₂ were encapsulated within the β-CD's cavity to form a 2:1 stoichiometry host–guest compound. The inclusion constant calculated was 1.27 × 10⁴ (L/mol)². A spectrofluorimetric method for the determination of 2H1NA in bulk aqueous solution in the presence of β-CD was developed based on the great enhancement of the fluorescence intensity of 2H1NA. The linear relationship was obtained in the range of 9.00 × 10^?7 to 2.50 × 10^?5 mol/L and the detection limit was 8.00 × 10^?7 mol/L. The proposed method was successfully applied to determine 2H1NA in waste water with recoveries of 97–104%.     

Excimer fluorescence and structures of the inclusion complexes of β-cyclodextrin with naphthalene and its derivatives

Fluorescence of the inclusion complexes with different compositions formed by naphthalene-h₈, naphthalene-d₈, 2,7-dimethylnaphthalene (DMN), and 2-benzylnaphthalene (BN) with β-cyclodextrin (β-CD) in water was studied. Two types of fluorescence are observed, monomer (MF) and excimer (EF_ fluorescence. The excimer fluorescence of the 2∶2 complex emitted by aggregated light-dispersing crystals forming a precipitate, whereas is the MF is concentrations, EF predominates for the resulting complexes. A proposed structure of the inclusion complexes was derived from MNDO/PM3 semiempirical quantum-chemical calculations. The EF is caused by the structure of the complex, in which both naphthalene molecules are separated by a distance of 4.7 Å: they lie in parallel orientation to each other, whereby one ring is displaced from the other by one-fourth of the length of the naphthalene ring. The complexes of 2,7-DMN and 2-benzylnaphthalene with β-CD do not exhibit EF. For the 2∶2 complex of 2,7-DMN with β-CD, this is due to the fact that the aromatic fragments are removed too far from one another 2-Benzylnaphthalene is unable to form an inclusion complex with β-CD, in whose structure the aromatic fragments inside the cavity could be arranged in parallel planes; instead, it forms a 1∶2 complex with β-CD.     

β-Cyclodextrin functionalized gold nanoparticles: characterization and its analytical application for l-tyrosine

β-Cyclodextrin functionalized gold nanoparticles (β-CD-Au NPs) were synthesized and characterized. The interaction of β-CD-Au NPs with l-tyrosine (l-Tyr) is studied by fluorescence and absorption spectroscopy. β-CD-Au NPs was found to remarkably quench fluorescence of l-Tyr at 305 nm. Experimental conditions including media acidity, temperature and concentration of buffer were examined for the inclusion formation. Furthermore, fluorescence resonance energy transfer occurred with Föster radius 2.39 nm. Apparent binding constants and corresponding thermodynamic parameters at different temperatures were calculated by Stern–Volmer equation and thermodynamic formula, respectively. The binding constant declines with the increasing temperature illustrating static quenching exists and the binding l-Tyr on β-CD-Au NPs is a spontaneous molecular interaction process in which entropy and Gibbs free energy decreases. Hydrophobic interaction and van der Waals forces could be in dominant action in the formation of the complex. The concentration of l-Tyr is proportional to decrease of the fluorescence intensity in the range of 0.02–1.5 μM with the detection limit (S/N = 3) of 1.6 nM. There is little interference from the coexisting substances normally used as the pharmaceutical main compositions. The proposed method combined the unique physical and chemical properties of the gold core with the molecular recognition ability of β-CD and possessed high sensitivity and good selectivety. It has been successfully applied to determination of l-Tyr in compound amino acid injection.     

Synergistic enhancement of the fluorescence intensity of 4,5-benzopiaselenol by surfactants and β-cyclodextrin in aqueous solution

The synergistic enhancement of the fluorescence intensity of 4,5-benzopiaselenol (I _F ^Se-DAN ) by surfactants (Sf) and -cyclodextrin (-CD) has been studied. The (I _F ^Se-DAN ) in sodium dodecyl sulfate (SDS)//gb-CD was approximately 30 times greater than that in water, and 5–6 times greater than that in either SDS or -CD solutions alone, and a blue-shift of the emission wavelength was observed.¹H-NMR experiments and determination of CMC values of Se-DAN/-CD, Se-DAN/SDS, and Se-DAN/SDS/-CD systems reveal that the synergistic fluorescence enhancement was produced by the SDS monomer/-CD inclusion complex. In essence, the synergistic enhancement is due to the altered microenvironment experienced by Se-DAN upon its transfer from water to the hydrophobic cavity upon complexation.     

Spectrofluorometry study of β-cyclodextrin and N-phenyl-1-naphthylamine inclusion complex and its analytical application via artificial neural network

The interaction between β-cyclodextrin (βCD) and N-phenyl-1-naphthylamine has been studied spectrofluorimetrically and found to form a 1:1 (βCD:NPN) inclusion complex at optimum conditions of pH 8 with the formation time of 120?s. The association constant of the complex was established to be 6.0?×?10²?M, while a remarkable enhancement in fluorescence intensity was also observed at 445?nm with excitation of 334?nm. A spectroflurometric method for the detection of N-phenyl-1-naphthylamine has been developed having a dynamic range linear up to 4.67?×?10^?7?M with a limit of detection of 0.58?nM. The repeatability study at two different βCD concentrations of 1.0?×?10^?4 and 4.0?×?10^?4?M was found to give RSD values of 2.40 and 1.42%, respectively. Artificial neural network (ANN) has been utilised to model the analytical system and successfully extended the analytical dynamic range up to 8.0?×?10^?7?M from the original 4.67?×?10^?7?M, brief network training and the optimum parameters of are described in this work.     

The effect of aluminum additions on the structural and hydrogen absorption properties of AB5 alloys with particular reference to the LaNi5−xAlx ternary alloy system

The dissociation pressures of the hydrides LaNi_4.6Al_0.4H₆, LaNi_4.5Al_0.5H₆, CFMNi_4.8Al_0.2H₆ (CFM = cerium-free mischmetal), CFMNi_4.6Al_0.4H₆ and YNi₄AlH₄ were studied. In all cases, the aluminum additions were found greatly to reduce the plateau pressure of the ANi_5−x Al_x hydride compared with that of the corresponding ANi₅ hydride (A = La, CFM, Y). LaNi_4.6Al_0.4 and LaNi_4.5Al_0.5 were specially prepared homogeneous alloys whose enthalpies and entropies of transition were calculated as − 8.7 kcal (mol H₂)⁻¹, − 9.2 kcal (mol H₂)⁻¹ − 26.1 cal (mol H₂)⁻¹ deg⁻¹ and 26.6 cal (mol H₂)⁻¹ deg⁻¹, respectively. A crystallographic model of LaNi₄Al is shown and consideration of the nearest neighbor atom distribution leads to a rationalization of the observed linear relationship between the enthalpy change ΔH and the Al composition. A recently proposed model of hydrogen interstitial site occupation is examined in the light of the present data. Finally, correlations of hydride dissociation pressures with either alloy heats of formation or alloy cell volumes are discussed.     

The preparation and fluorescence properties of europium nanoparticles

A new structured metallic nanomaterial of europium nanoparticle was prepared using tannic acid as the reductive agent,and nanoeuropium protein conjugates were synthesized by the method of lipoic acid modification on the surface of nanoparticle,which opens a new field of application of lanthanides in nanotechniques.Their properties were also characterized by UV-vis absorption spectroscopy,transmission electron microscopy (TEM),and fluorescence spectroscopy.The europium nanoparticle and its protein conjugates solution were stable and water-soluble.The fluorescence intensity of the composite europium nanoparticles was significantly increased in the presence of trace protein,and was linear proportional to the concentration of proteins under optimum conditions.According to this,a fluorimetric method for the determination of protein was developed in this paper.