Interaction of Polyelectrolyte with Fluorocarbon Surfactant in Aqueous Solution

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Kinetic and Mechanistic Studies on [Zn(II)-Gly-Phe]+–Ninhydrin Reaction in Aqueous and Cationic CTAB Surfactant Micelles

The rates of reaction between metal-dipeptide complex ([Zn(II)-Gly-Phe]⁺) and ninhydrin have been determined in aqueous and aqueous–cationic micelles of cetyltrimethylammonium bromide (CTAB) at 70°C and pH 5.0. The rate data indicate that the reaction follows the template reaction mechanism in both the media. The reaction followed a first-order and fractional-order kinetics with respect to [Zn(II)-Gly-Phe]⁺ and [ninhydrin], respectively, in the excess of ninhydrin over [Zn(II)-Gly-Phe]⁺. The rate constant is affected by [CTAB] changes and maximum rate enhancement is approximately three-fold. CTAB micelles decrease the activation enthalpy and make the activation entropy less negative. Quantitative kinetic analysis of rate constant (k _ψ)–[CTAB] data was performed on the basis of pseudophase model of the micelles (proposed by Menger and Portnoy and developed by Bunton). The values of binding constants K _S for [Zn(II)-Gly-Phe]⁺ and K _N for ninhydrin with micelles are calculated with the help of observed kinetic data. The results obtained in micellar medium are treated quantitatively on the basis of pseudophase model.     

Study of the Interaction between Cationic Surfactant and Polyacryldmide with Various Hydrolysis Degree

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Probing the Interaction Between a Surfactant–Cobalt(III) Complex and Bovine Serum Albumin

The mechanism of binding of the surfactant–cobalt(III) complex, cis-[Co(phen)₂(C₁₄H₂₉NH₂)Cl](ClO₄)₂⋅3H₂O (phen = 1,10-phenanthroline, C₁₄H₂₉NH₂ = tetradecylamine) with bovine serum albumin (BSA) was investigated by UV–vis absorption, circular dichroism (CD) and fluorescence spectroscopic techniques. The results of fluorescence titration revealed that the surfactant–cobalt(III) complex quenched the intrinsic fluorescence of BSA through a combination of static and dynamic quenching. The apparent binding constant (K _a) and number of binding sites (n) were calculated below and above the critical micelle concentration (CMC). The thermodynamic parameters determined by the van’t Hoff analysis of the constants (ΔH ^∘=14.87 kJ⋅mol⁻¹; ΔS ^∘=152.88 J⋅mol⁻¹⋅K⁻¹ below the CMC and 25.70 kJ⋅mol⁻¹ and 243.14 J⋅mol⁻¹⋅K⁻¹, respectively, above the CMC) clearly indicate that the binding is entropy-driven and enthalpically disfavored. Based on F?rster’s theory of non-radiation energy transfer, the binding distance, r, between donor (BSA) and the acceptor (surfactant–cobalt(III) complex) was evaluated. UV–vis, CD and synchronous fluorescence spectral results showed that the binding of the surfactant–cobalt(III) complex to BSA induced conformational changes in BSA.     

UV–Spectral Study on the Effects of Inert Salts on the Nonionic Micellar Solubilization of Phenyl Salicylate in the Absence and Presence of a Cationic Surfactant Under Alkaline Aqueous Medium

The values of the fraction of ionizes phenyl salicylate, f_PS-, obtained from initial absorbance measurement of phenyl salicylate at 350 nm, remain unchanged with the increase in [CH₃CO₂Na] from 0.0 to 0.7 M at 0.01 M NaOH (f_PS- ≈ 0.70) and 0.02 M NaOH (f_PS- ≈ 0.93). The values of f_PS- decrease from ～ 1.0 to 0.90 and ～ 1.0 to 0.84 with the increase in respective [CH₃CO₂Na] and [NaBr] from 0.0 to 0.6 M at 0.01 M NaOH, 0.02 M C₁₂E₂₃(=C₁₂H₂₅(OCH₂CH₂)₂₃OH) and 0.01 M CTABr (=C₁₆H₃₃NMe₃Br).     

Kinetics and Mechanism of 4-Nitrotoluene Oxidation with Ozone in an Acetic Acid Solution in the Presence of a Metal–Bromide Catalyst

The kinetics and mechanism of a reaction between ozone and 4-nitrotoluene in an acetic acid solution in the presence of a cobalt–bromide catalyst were studied at 100°. Under these conditions, 4-nitrobenzoic acid was the main reaction product (96.6%). The rate of oxidation exhibited a first order with respect to the substrate, ozone, and the catalyst and a zero order with respect to oxygen. The main stages of the catalytic cycle were considered. It is believed that the selective oxidation of 4-nitrotoluene at the methyl group in the presence of a catalyst occurs as a nonchain ion–radical process, in which the role of ozone is reduced to the generation of an active catalyst species (Co³⁺Br^– Co²⁺Br^·). This species involves 4-nitrotoluene in the oxidation process at a high rate.     

Inclusion Complex of β-cyclodextrin with CTAB in Aqueous Solution

Cetyltrimethylammonium bromide (CTAB)/potassium bromide (KBr) micellar system has been used as a viscosity probe to study the inclusion complexation between β-cyclodextrin (β-CD) and CTAB. Viscosity measurements show that the inclusion complexation between β-CD and CTAB may cause the breakdown of CTAB/KBr wormlike micelles, resulting in the decrease of the solution viscosity. The viscosity minimum at C_β-CD/C_CTAB=2 indicate the molecular ratio of host molecule to guest molecule is 2:1 in the β-CD/CTAB inclusion complex.     

Interaction of the La(III)–Morin Complex with Human Serum Albumin

Journal of Solution Chemistry - Lanthanum (La) is one of the most reactive rare earth elements, whose carbonate had been approved by the FDA for marketing as a treatment drug for hyperphosphatemia....     

Spectroscopic Study on Interaction of Lomefloxacin with Human Serum Albumin in the Presence of Copper Ion

The interaction of lomefloxacin （LMF） with human serum albumin （HSA） in the presence of copper ions in a physiological medium and its thermodynamic characteristics were investigated by multi-spectroscopy. The experimental results showed that both LMF and LMF-Cu^2＋ could quench the fluorescence of HSA with a static quenching mechanism, indicating that LMF or LMF-Cu^2＋ could react with HSA. The apparent binding constants/numbers of binding sites were estimated as 4.924± 105 Lomol 1/1.473 for LMF-HSA, 8.990± 104 L·mol^-1/1.785 for LMF- Cu^2＋-HSA, 1.10± 105 L·mol^-1/1.21 for LMF-Cu^2＋ and 7.30± 102 L·mol^-1/0.82 for HSA-Cu^2＋, respectively. AH and AS for LMF-HSA system were calculated to be --2.189 kJ·mol^-1 and 61.25 J·mol^-1·K^-1, while those for LMF-Cu^2＋-HSA system were -7.401 kJ·mol^-1 and 47.63 J·mol^-1·K^-1 Although the values of AH and AS in these two systems were different, the treads were similar, which indicated that electrostatic interactions in these two systems played a major role. According to Forster theory, the distances were given as 5.006 nm for HSA-LMF and 4.709 nm for HSA-LMF-Cu^2＋. Synchronous fluorescence and circular dichroism spectra confirmed further that the conformations of human serum albumin before and after interacting with LMF or LMF-Cu^2＋ were different. All the results revealed that copper ions promoted the interaction of lomefloxacin with human serum albumin.     

Experimental and Theoretical Study of the Stability of the Complex Fisetin–Cu(II) and A Comparative Study of Free Ligand and Complex Interaction with Molecular Singlet Oxygen

In this work, the flavonol fisetin was selected in order to study its reactivity against Cu(II), a metal ion of interest in biological media and industry. The stoichiometry and apparent formation constant of the complex in ethanolic medium at 25°C were evaluated using spectrophotometric techniques. The resulting stoichiometry was a 1:1 ligand:metal complex, and a log K = 5.17 ± 0.12 was determined. Since two possible chelation sites can be proposed for the complex formation, quantum chemistry calculations were performed on these structures. Calculations suggest that the hydroxyl-keto site is more stable for the complex formation than the catechol site. Flavonoids could exert protection against oxidative damage caused by reactive oxygen species, and this biological activity could be affected by chelation with metal ions. This led us to perform a study on the interaction of both, free flavonoid and complex, with reactive oxygen species. Our results showed both compounds quench molecular singlet oxygen photogenerated with visible light, mainly in a physical fashion. In order to analyze a possible protective effect of flavonoid and its complex against oxidative damage in biological environments, the amino acid tryptophan was selected as a model oxidation system. Free flavonoid does not have a marked protective effect, whereas its complex showed a relevant protective effect.     

Interaction of Fluorinated Alcohols with the β-Cyclodextrin/Acridine Complex

Abstract

The role of hydrogen bonding vs. hydrophobic interactions are evaluated with respect to the driving forces for alcohol complexation with β-cyclodextrin (β-CD). Simultaneous information is gathered regarding these considerations in the binding of acridine to the β-CD molecule.     

Anomeric and Enantiomeric 2’-Deoxycytidines: Base Pair Stability in the Absence and Presence of Silver Ions

Dodecamer duplex DNA containing anomeric (α/β-d ) and enantiomeric (β-l /β-d ) 2’-deoxycytidine mismatches was studied with respect to base pair stability in the absence and presence of silver ions. Stable duplexes with silver-mediated cytosine–cytosine pairs were formed by all anomeric and enantiomeric combinations. Stability changes were observed depending on the composition of the mismatches. Most strikingly, the new silver-mediated base pair of anomeric α-d -dC with enantiomeric β-l -dC is superior to the well-noted β-d /β-d -dC pair in terms of stability. CD spectra were used to follow global helical changes of DNA structure.     

Formation and Extraction of Niobium(V) Complex with Xylenol Orange in the Presence of a 4-Pyridone Derivative

Xylenol orange (XO) is a suitable reagent for the spectrophotometric determination of niobium in a weakly acidic medium. The present study shows that the addition of 3-hydroxy-2-methyl-1-phenyl-4-pyridone (HX) influences the complex formation as well as the spectroscopic properties of this colored system. To prevent formation of niobium(V) hydrolyzed species in water, tartaric acid was used when preparing the niobium stock solution. The red-violet colored complex formed by heating niobium(V) with xylenol orange (XO) in the presence of HX at pH=3 has a maximum absorption wavelength at 565 nm. The complex can be extracted by a chloroform solution of tetraphenylphosphonium (TPP) chloride. The optimum reaction conditions and other parameters for complex formation have been evaluated. The mechanism of extraction is probably based on the formation of the associated ion pair between the tetraphenylphosphonium cation and the mixed Nb(V)-XO-HX anion. The extracted complex in chloroform showed a maximum absorbance at 585 nm with the corresponding molar absorption coefficient being 3.72×10⁴ L⋅mol⁻¹⋅cm⁻¹, and obeys Beer’s law in the range 3×10⁻⁶ to 3×10⁻⁵ mol⋅L⁻¹.     

Physicochemical and Catalytic Properties of Ni,H/ZSM-5 and Ni,H/ZSM-5–Binder Catalysts Prepared in the Absence and in the Presence of Binder

Kinetics and Catalysis - Physicochemical and catalytic properties of H/ZSM-5 and Ni,H/ZSM-5 along with Ni,H/ZSM-5–Al2O3 (1 : 1) systems were examined. The systems with a binder were prepared...     

Studies of the Interaction of the Salicylideneserinatecopper(II) Complex with β-Cyclodextrin: Characterization and Reactivity of the Inclusion Compound

The compound formed by the copper-Schiff base complex salicylideneserinatecopper(II), [Cu(sal-ser)(H2O)], interacting with -cyclodextrin was prepared, and characterized in the solid state by infrared, UV-visible and EPR spectroscopies, X- ray diffraction, and thermoanalytical techniques. The catalytic activity of this compound, [Cu(sal-ser)CD], in the decomposition of hydrogen peroxide, and in the dismutation of superoxide radicals was also verified, in comparison with the reactivity of the free complex, in aqueous solution. In both cases, a decreasing in the reaction rate was observed for the CD-containing compound. The results of structural characterization, in addition to the substantial differences observed in the catalytic activities of the compounds, are indicative of partial insertion of the copper complex in the cavity of the oligosaccharide.     

Alkylation of 2-Sulfanylbenzoxazole with α-Iodoketones in the Absence of Bases

Reaction of 2-sulfanylbenzoxazole with 1-iodopropan-2-one, 2-iodo-1-phenylethanone, and 2-iodo-1-(thiophen-2-yl)ethanone without solvent and bases afforded bis(benzoxazol-2-yl)disulfonium derivatives in a single preparative stage. The reaction proceeds as a domino-process and includes the alkylation of a sulfanyl group of benzoxazole, the reduction of iodoketone with hydrogen iodide, the oxidation of 2-sulfanylbenzoxazole to disulfide, the alkylation of disulfide atoms of sulfur, and the formation of triiodideanions. The yield of disulfonium derivatives increases twice in the presence of equimolar amount of iodine.     

Synthesis of Metal Porphyrins Tailed with Salicylic Acid and their Interaction with Bovine Serum Albumin

A synthetic method of porphyrins tailed with salicylic substituents is described.Reaction of bromoalkoxyphenyl porphyrin 1 with salicylic acid gave porphyrins 2-5. These new compounds were confirmed by ^1H NMR, IR, UV-vis, MS and elemental analysis, and observed their interaction with bovine serum albumin (BSA) in fluorescence spectrum.