A 1H NMR study of 1,4-bis(N-hexadecyl-N, N-dimethylammonium)butane dibromide/sodium anthranilate system: spherical to rod-shaped transition

The effect of addition of sodium anthranilate to 5 mM micellar solutions of gemini surfactant 1,4-bis(N-hexadecyl-N,N-dimethylammonium)butane dibromide is investigated by ¹H NMR. The solubilization site of anthranilate anion near the micellar surface is inferred. In the micelles, the An⁻ ions intercalate among the surfactant headgroups producing morphological changes.     

MICELLIZATION STUDIES OF DODECYL BENZENESULFONIC ACID AND ITS INTERACTION WITH POLYVINYLPYRROLIDONE

Dodecyl benzenesulfonic acid (DBSA) surfactant was used in the present study to find the effect of concentration on its electrical conductance in solution from 293-323K above and below the critical micelle concentration (CMC). The micellization parameters i.e. degree of counter ion binding (β), aggregation number (n) and number of counter ion micelle(m) were measured. The interaction of DBSA with polyvinylpyrrolidone (PVP) was also studied at 293K throughconductance and surface tension measure ments. A number of important parameters i.e. critical aggregation concentration (CAC), Gibb‘s free energy (△G) and binding ratio (R) were determined and the effect of NaCl on the CAC and polymer saturation point (PSP) was also investigated.     

O-silylated enolate phenylthialkylation: A synthesis of α,β-unsaturated 5- and 6-membered lactones.

ZnBr₂-catalysed phenylthioalkylation of ketene bis(trimethylsilyl)acetals, obtained from carboxylic acids, with appropriate α-chlorosulphides can be used to prepare γ- and δ- lactones.     

Enantiomeric Separation of Adrenergic Amines in Citrus Species, Related Genera and Dietary Supplements by Capillary Electrophoresis

Citrus aurantium L. (Rutaceae) fruit extracts have recently been used for weight loss. Among the adrenergic amines the most important active constituent is the sympathomimetic compound synephrine and commercially available extracts are standardized for their content of this active principle. A capillary electrophoresis method was developed for the quantitative and qualitative determination of d-synephrine, l-synephrine, d-octopamine, l-octopamine, tyramine, n-methyl tyramine and hordenine. The electrophoretic separation was performed using a 75 cm × 50 µm ID (66.5 cm effective length) fused silica capillary. The samples were injected by pressure for 5s at 50 mbar and the running voltage was 30 kV at the injector end of the capillary. The method developed was successively applied to the determination of the adrenergic amines in dietary supplements, in various Citrus species including Citrus aurantium, jams and juices. Synephrine was the main component and present in the levels from 0.02–0.17% in various Citrus species and 0.42–69.28 mg in dietary supplements claiming to contain Citrus aurantium. Parameters affecting the resolution between (+) and (−)-enantiomers, such as pH, cyclodextrin concentration, temperature, organic modifier, buffer concentration and capillary dimensions were reported.     

Helical poly(3-methyl-4-vinylpyridine)/amino acid complexes: preparation, characterization, and biocompatibility

Helical poly(3-methyl-4-vinylpyridine) (P3M4VP)/amino acid complexes have been prepared via acid-base reaction of the achiral polymer with D and L amino acids: alanine, leucine, valine, serine and phenylalanine. The circular dichroism (CD) spectra of P3M4VP/D- and L-alanine complexes in CH(3)OH/H(2)O show opposing (near mirror image) Cotton effect signals at 278.4, 274.8 and 270.8 nm, indicating the formation of enantiomeric secondary structures. The formation of the enantiomeric structures is supported by observed [alpha](D)(25) values of -3.0 and +3.0 for the P3M4VP/D-alanine and P3M4VP/L-alanine complexes, respectively. The preparation of helical P3M4VP/amino acid complexes has been carried out in CH(3)OH and H(2)O at pH 1.8 and 2.7. The intensities of the Cotton effect signals were good. For example, for the P3M4VP/L-alanine complexes in CH(3)OH/H(2)O and H(2)O (pH 1.8), the second Cotton effect signal around 275-277 nm show [theta;] values of 49 980 and 79 210 deg . cm(2) . dmol(-1), respectively. The formation of the helical secondary structure is rapid. The acid-base reaction between P3M4VP and L-alanine in CH(3)OH/H(2)O, in 10 min, show a CD spectrum with Cotton effect signals at 274 and 272 nm with [theta] values of 27,000 deg . cm(2) . dmol(-1) and -36,000 deg . cm(2) . dmol(-1), respectively. P3M4VP permits ready conformational reorientation on complexation with amino acids, but once the helical P3M4VP/amino acid complexes are formed, it is stable at room temperature. P3M4VP is not compatible with HeLa ovarian cancer cells, but the helical P3M4VP/amino acid complexes are compatible with HeLa cells. The complexes minimally interfere with the adhesion and growth of HeLa cells on complex surfaces. Helical poly(3-methyl-4-vinylpyridine)/D- and L-alanine complexes support the attachment and growth of HeLa cells. The micrographs shows HeLa cells after three days: left panel: on P3M4VP/L-alanine complex; right panel: on P3M4VP/D-alanine complex.     

Transient rheological behavior of lyotropic (acetyl)(ethyl)cellulose/m-cresol solutions

The chiroptical properties and transient rheological behavior of (acetyl)(ethyl)cellulose (AEC) m-cresol liquid crystalline solutions have been investigated. Chiroptical properties were manipulated through (i) increasing degree of acetylation of ethyl cellulose (EC), and (ii) blending AEC with EC. At the same average degree of acetylation (DA), the chiroptical properties of pure AEC were different from those of the EC/AEC mixtures. However, at the same DA, the AEC and mixed AEC/EC solutions showed similar steady state flow and oscillatory behaviors, but the transient behaviors were different. At high flow rates the mixed AEC/EC solutions exhibited double recoil after cessation of steady-state flow, whereas the AEC solutions showed double recoil only in the high DA AEC solutions. All solutions, pure and mixed, had the same stress relaxation behavior. Both pitch and handedness affected the transient behavior. After cessation of high shear rate flow, the rate of modulus evolution decreased with increasing pitch, and was faster in right-handed mesophases than in left-handed ones at a similar pitch.     

Novel laccase redox mediators: spectral, electrochemical, and kinetic properties

The screening of potential redox mediators for laccase was performed using homogeneous enzyme preparations from Coriolus hirsutus and Coriolus zonatus. It was discovered that derivatives of 1-phenyl-3-methyl-pyrazolones were efficient substrates for the laccases. The characterization of two representatives of the 1-phenyl-pyrazolone class, sodium 1-phenyl-3-methyl-4- methylamino-pyrazolone-5-N(4)-methanesulfonate and 1-(3'-sulfophenyl)-3- methylpyrazolone-5, in the reaction catalyzed by laccase was carried out using spectral, electrochemical, and enzyme kinetics methods. The kinetic parameters for the oxidation of the newly discovered substrates were comparable with those for 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) oxidation by laccase. Electrochemical experiments demonstrated that oxidation of these compounds yielded two high-potential intermediates capable of oxidizing veratryl alcohol, which was used as a lignin model substrate, to the corresponding aldehyde and acid. 1-(3'-Sulfophenyl)-3- methylpyrazolone-5 was about 30-40% as effective in degrading veratryl alcohol compared to ABTS as judged from high-performance liquid chromatography kinetic studies. 1-Phenyl-3-methyl-pyrazolones may be of commercial interest for oxidoreductase-catalyzed biodegradation of organic compounds.     

Thermostability of <Emphasis Type="Italic">Cromobacterium viscosum</Emphasis> lipase in AOT/isooctane reverse micelle

The thermostability of Cromobacterium viscosum lip ase (EC 3.1.1.3) entrapped in AOT (sodium bis-[2-ethylhexyl] sulfosuccinate) reverse micelles was in creased by the addition of short-chain polyethylene glycol (PEG 400). Two different approaches were considered: (1) the determination of half-life time and (2) the mechanistic analysis of deactivation kinetics. The half-life of lipase entrapped in AOT/isooctane reverse micelles with PEG 400 at 60°C was 28h, ninefold higher than that in reverse micelles without PEG 400. The lip ase entrapped in both reverse micellar systems followed a series-type deactivation mechanism involving two first-order steps. The deactivation constant for the first step at 60°C in PEG containing reverse micelles was 0.055 h¹¹, 11-fold lower than that in reverse micelles without PEG, whereas it remained almost constant for the second step. The inactivation energy of the lip ase entrapped in reverse micelles with and without PEG 400 was 88.12 and 21.97 kJ/mol, respectively.     

Effects of

Effects of cetyltrimethylammonium bromide (CTABr) micelles on second-order rate constants (k(n)(obs)) for nucleophilic reactions of amines (piperidine and n-butylamine) with ionized phenyl salicylate (PS(-)) reveal a nonlinear decrease with the increase in [D(n)] (where [D(n)] = [CTABr](T) - cmc) at a constant [NaBr] and 35 degrees C. The observed data, at a constant [NaBr], fit reasonably well to a pseudophase model of micelles, and such a data fit gives kinetic parameters such as CTABr micellar binding canstant (K(S)) of PS(-). The effect of [NaBr] upon K(S) is explained with the empirical relationship K(S) = K(S)(0)/(1 + psi[NaBr]), where psi is an empirical parameter.     

Changes produced in the electrical resistivity of ErH2 thin films when converted to ErH3 due to hydrogen treatment

The resistivity of thin films (80–200 Å) of ErH₂ increases sharply when heated for 2 h at 300 °C in vacuum in the presence of hydrogen gas at 10^–2 Torr. This confirms that the films, originally metallic conductor, have become converted to semiconducting ErH₃ which is in conformity with the structural studies. The negative values of TCR also indicate the semiconducting nature of the hydrogen treated films. Activation energies of the films have been evaluated.