betadex and 2-(4-toluidino)-6-naphthalenesulfonic-acid

Reductive alkylation of the amino group of chitosan with β-cyclodextrin (CD) aldehyde derivatives, i.e., 6-deoxy-6-(4-oxobutyramido)-β-CD and 6-oxo-β-CD, gave two β-CD-linked chitosan derivatives with C4 (4-butylamido) and C0 linking arms, respectively. Degree of substitution (D.S.) of both C4-β-CD and C0-β-CD linked chitosan was controlled by the ratio of starting materials. The structures of the products were confirmed by (1)H and (13)C NMR and FT-IR spectra. Their inclusion properties of C4-β-CD (D.S. 18%) and C0-β-CD linked chitosan (D.S. 17%) with a fluorescent probe, 6-(p-toluidino)-2-napthalene-6-sulfonate (TNS) were investigated in acetate buffer (pH 4.3) at 25°C. Continuous variation of Job's method revealed that the stoichiometry of inclusion complex of C4-β-CD linked chitosan-TNS was 1:1, whereas that of C0-β-CD linked chitosan was not 1:1. The stability constant of C4-β-CD linked chitosan determined by Benesi-Hildebrand plot was 2.3×10(3)M(-1). These results suggested that length of the linking arms between CD and chitosan is influenced on their inclusion property.

Topics: beta-Cyclodextrins; Chitosan; Drug Stability; Naphthalenesulfonates

A series of substituted benzoyl modified beta-cyclodextrins, including mono-6-O-(p-methylbenzoyl)-beta-CD (1), mono-6-O-(m-methylbenzoyl)-beta-CD (2), mono-6-O-(o-methylbenzoyl)-beta-CD (3), mono-6-O-(p-methoxylbenzoyl)-beta-CD (4), mono-6-O-(m-methoxylbenzoyl)-beta-CD (5), mono-6-O-(o-methoxylbenzoyl)-beta-CD (6), mono-6-O-(m, p-dimethoxylbenzoyl)]-beta-CD (7), mono-6-O-(o,m-dimethoxylbenzoyl)-beta-CD (8), and mono-(6-O-benzoyl)-beta-CD (9) were synthesized and their inclusion properties were studied by using fluorescence spectroscopy. The binding constants (K(a)) of the modified beta-CD derivatives with 2-p-toluidinylnaphthalene-6-sulfonate (TNS) were determined on the basis of the fluorescence spectroscopy. The effect of types and location of substituted groups of the benzene ring of the modified beta-cyclodextrins on the binding property was discussed. Results indicated that the substituents had significant influences on the binding abilities of modified beta-cyclodextrins.

Topics: beta-Cyclodextrins; Naphthalenesulfonates; Spectrometry, Fluorescence

Three beta-cyclodextrin (beta-CyD) derivatives with crown ether units, that is N-(4'-benzo-15-crown-5)-6-imino-6-deoxy-beta-CyD (2), 6,6'-[N-(4,4'-dibenzo-18-crown-6)-imino]-bridged bis(beta-CyD)(3), and 2,2'-[O-(4',5'-benzo-15-crown-5)-ethyl]-bridged bis (beta-CyD)(5), were synthesized as cooperative recognition receptor models. Their molecular binding behavior with four representative fluorescent dyes, i.e., ammonium 8-anilino-1-naphthalenesulfonate (ANS), sodium-6-toluidino-2-naphthalene-sulfonate (TNS), Acridine Red (AR) and Rhodamine B (RhB), was investigated in buffer solutions (pH = 7.20) at 25 degreesC by means of circular dichroism, NMR and fluorescence spectroscopy. 2D-ROESY experiments showed that dyad host 2 and triad host 3 adopted a CyD-guest-crown ether binding mode, while triad host 5 adopted a CyD-guest-CyD binding mode, upon inclusion complexation with guest molecules. Therefore, hosts 2 and 3 showed high molecular recognition ability towards charged guests, giving an enhanced binding ability up to 115 times for ANS by 3 and fairly high molecular selectivity up to 1450 times for the ANS/AR pair by 2 as compared with native beta-CyD in an aqueous phosphate buffer solution. On the other hand, host 5 was found to be able to effectively recognize the shape of a guest molecule, showing significantly higher binding ability towards linear guests. The binding affinities and molecular recognition abilities of these CyD-crown ether conjugates towards guest molecules are discussed from the viewpoint of electrostatic and/or hydrophobic interactions, size/shape-fit concept, and multiple recognition mechanism between host and guest.

Topics: Anilino Naphthalenesulfonates; beta-Cyclodextrins; Binding Sites; Circular Dichroism; Crown Ethers; Cyclodextrins; Fluorescent Dyes; Hydrophobic and Hydrophilic Interactions; Ligands; Magnetic Resonance Spectroscopy; Models, Chemical; Models, Molecular; Molecular Structure; Naphthalenesulfonates; Rhodamines; Spectrometry, Fluorescence; Static Electricity

6-p-Toluidinylnaphthalene-2-sulfonate (TNS) is used as a fluorescent probe for exploring hydrophobic regions of several biological substances, such as proteins, and studying solution state folding behaviour. The current study examines the complexation of TNS with 2-hydroxypropyl-beta-cyclodextrin (HPbetaCD) in aqueous solution, mainly by ultraviolet spectrophotometry using various concentrations of HPbetaCD. The structure of HPbetaCD was confirmed by using positive-ion electrospray ionization (ESI+) mass spectrometry. The complex was examined for its stoichiometry applying the continuous variation (Job plot) method. Also, the kinetics of the complex formation was monitored and the determination of the stability constant was calculated. For this purpose, the spectrophotometric properties of TNS were observed in the presence of increasing concentrations of HPbetaCD applying the transformed Benesi-Hildebrand linear model as well as a nonlinear one. The results suggest that TNS forms a stable complex of 1:1 molar ratio, at least at the examined concentrations. Furthermore, from the measurements of 1H nuclear magnetic resonance (1H NMR) spectra, interactions between protons of TNS with HPbetaCD were determined.

Topics: 2-Hydroxypropyl-beta-cyclodextrin; beta-Cyclodextrins; Chemistry; Cyclodextrins; Fluorescent Dyes; Kinetics; Magnetic Resonance Spectroscopy; Models, Chemical; Models, Theoretical; Naphthalenesulfonates; Thermodynamics

The present study examines the complexation of beta-cyclodextrin (beta-CD) with 6-p-toluidinylnaphthalene-2-sulfonate (TNS), a fluorescent probe for exploring hydrophobic regions of several biological substances. The complexation was monitored in aqueous solution by ultraviolet spectrophotometry. At first, the stoichiometry of the formed complex was examined by applying the continuous variation (Job plot) method. Next, the kinetic of the complex formation as well as the determination of the stability constant were calculated by monitoring the spectrophotometric properties of TNS in the presence of increasing concentrations of beta-CD applying both linear and nonlinear models. The results suggested that TNS forms a stable complex with beta-CD with a stability constant of 1109 M(-1) and 1:1 molar ratio, at least at the examined concentrations.

Topics: beta-Cyclodextrins; Cyclodextrins; Drug Interactions; Drug Stability; Fluorescent Dyes; Food Additives; Linear Models; Naphthalenesulfonates; Nonlinear Dynamics; Spectrophotometry, Ultraviolet

The interaction of 6-p-toluidinylnaphthalene-2-sulfonate (TNS) with beta-cyclodextrin was investigated in 0.1 M phosphate buffer at pH 7.4 by fluorescence spectroscopy. Using the fluorescence enhancement of TNS in the presence of beta-cyclodextrin, the thermodynamic parameters for the formation of two kinds of the inclusion complex (molar ratio of beta-cyclodextrin to TNS = 1:1 and 2:1) were determined as follows: delta G degree 1 (1:1 complex) = -20.0 kJ mol-1 at 25 degrees C, delta H degree 1 = -19.6 kJ mol-1, delta S degree 1 = -1.7 J mol-1 K-1, delta G degree 2 (2:1 complex) at 25 degrees C = -6.14 kJ mol-1, delta H degree 2 = -2.80 kJ mol-1, delta S degree 2 = 16.7 J mol-1 K-1. From the thermodynamic parameters, the main driving force for the 1:1 inclusion complex formation was considered to be the van der Waals-London dispersion force, while the contribution of the hydrophobic interaction was small. Also, the hydrogen bonding was suggested to contribute to the inclusion complex formation. The main driving force for the 2:1 inclusion complex formation was the hydrophobic interaction. Also, from the measurements of proton nuclear magnetic resonance spectra and studies with Corey-Pauling-Koltun atomic models, the probable structure was determined and discussed in connection with the thermodynamic parameters.

Topics: beta-Cyclodextrins; Cyclodextrins; Magnetic Resonance Spectroscopy; Naphthalenesulfonates; Spectrometry, Fluorescence; Sulfhydryl Reagents; Thermodynamics