Interactions between β-cyclodextrin and an amino acid-based anionic gemini surfactant derived from cysteine.

The interaction between β-cyclodextrin (β-CD) and an amino acid-based anionic gemini surfactant derived from cysteine (C(8)Cys)(2) was studied by three independent techniques: electrical conductivity, UV-Vis spectral displacement technique using phenolphthalein as probe, and (1)H NMR spectroscopy. The data obtained indicated the formation of a 1:1 inclusion complex between β-CD and the gemini surfactant studied and allowed for the determination of the binding constant, K(1), by considering this stoichiometry. Electrical conductivity, spectral displacement technique, and NMR chemical shift measurements, obtained for aqueous β-CD-surfactant systems, yielded consistent K(1) values in the order of 10(2) dm(3) mol(-1), typical of a weakly bound β-CD-surfactant complex.

Enzymatic Synthesis of the Flavone Glucosides, Prunin and Isoquercetin, and the Aglycones, Naringenin and Quercetin, with Selective α-L-Rhamnosidase and β-D-Glucosidase Activities of Naringinase.

The production of flavonoid glycosides by removing rhamnose from rutinosides can be accomplished through enzymatic catalysis. Naringinase is an enzyme complex, expressing both α-L-rhamnosidase and β-D-glucosidase activities, with application in glycosides hydrolysis. To produce monoglycosylated flavonoids with naringinase, the expression of β-D-glucosidase activity is not desirable leading to the need of expensive methods for α-L-rhamnosidase purification.

Mixed micelle formation between amino acid-based surfactants and phospholipids.

The mixed micelle formation in aqueous solutions between an anionic gemini surfactant derived from the amino acid cystine (C(8)Cys)(2), and the phospholipids 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC, a micelle-forming phospholipid) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC, a vesicle-forming phospholipid) has been studied by conductivity and the results compared with the ones obtained for the mixed systems with the single-chain surfactant derived from cysteine, C(8)Cys. Phospholipid-surfactant interactions were found to be synergistic in nature and dependent on the type of phospholipid and on surfactant hydrophobicity. Regular solution theory was used to analyse the gemini surfactant-DHPC binary mixtures and the interaction parameter, β(12), has been evaluated, as well as mixed micelle composition.

Dimeric and monomeric surfactants derived from sulfur-containing amino acids.

Anionic urea-based dimeric (gemini) surfactants derived from the amino acids L-cystine, D-cystine and DL-cystine, as well as monomeric surfactants derived from L-cysteine, L-methionine and L-cysteic acid were synthesized and their solution properties characterized by electrical conductivity, equilibrium surface tension, and steady-state fluorescence spectroscopy techniques. The geminis studied showed the lowest critical micelle concentration (cmc) values, however the monomeric cysteine counterpart exhibited superior efficiency in lowering surface tension, an unusual finding that can be attributed to the free sulfhydryl group. Chirality seems to play a role in the surface active properties of the gemini surfactants, but not on micelle formation.

α-Rhamnosidase and β-glucosidase expressed by naringinase immobilized on new ionic liquid sol-gel matrices: Activity and stability studies.

Novel ionic liquid (IL) sol-gel materials development, for enzyme immobilization, was the goal of this work. The deglycosylation of natural glycosides were performed with α-l-rhamnosidase and β-d-glucosidase activities expressed by naringinase. To attain that goal ILs with different structures were incorporated in TMOS/Glycerol sol-gel matrices and used on naringinase immobilization.

Gemini surfactant-protein interactions: effect of pH, temperature, and surfactant stereochemistry.

The interactions between bovine serum albumin (BSA) and gemini surfactants derived from cystine have been investigated and were compared with the conventional single-chain surfactant derived from cysteine. The influence of the stereochemistry of the gemini surfactant on its behavior toward BSA was also investigated, as well as the effects of pH and temperature. Electrical conductivity and surface tension measurements were used to obtain important system parameters such as critical aggregation concentration (cac), polymer saturation point (psp), degree of ionization (alpha), and the amount of surfactant binding to protein (M).

New urea-based surfactants derived from alpha,omega-amino acids.

New anionic urea-based surfactants derived from alpha,omega-amino acids and in particular from beta-alanine were synthesized and their solution properties characterized by electrical conductivity, equilibrium surface tension, and steady-state fluorescence spectroscopy techniques. Double-chain surfactants and the single-chain surfactant containing a sulfate head group exhibited the lowest critical micelle concentration (cmc) values and superior efficiency in lowering surface tension. All surfactants promoted adsorption relative to micellization, and micellar parameters were sensitive to the hydrophobicity of the amino acid residue.

Unusual solvent effect on a SN2 reaction. A quantum-mechanical and kinetic study of the Menshutkin reaction between 2-amino-1-methylbenzimidazole and iodomethane in the gas phase and in acetonitrile.

The quaternization reaction between 2-amino-1-methylbenzimidazole and iodomethane was investigated in the gas phase and in liquid acetonitrile. Both experimental and theoretical techniques were used in this study. In the experimental part of this work, accurate second-order rate constants were obtained for this reaction in acetonitrile from conductivity data in the 293-323 K temperature range and at ambient pressure.

The quaternisation reaction of phosphines and amines in aliphatic alcohols. A similarity analysis using the isokinetic, isosolvent and isoselective relationships.

Accurate second-order rate constants were measured at 5 K intervals in the temperature range 298.15-328.15 K for the quaternisation reaction of triethylphosphine with iodoethane in methanol, ethanol, propan-1-ol and butan-1-ol.