Direct biocatalysed synthesis of first sulfur-, selenium- and tellurium- containing l-ascorbyl hybrid derivatives with radical trapping and GPx-like properties.

6-O-l-Ascorbyl selenoesters, thioesters and telluroesters can be efficiently and directly prepared from l-ascorbic acid and suitable functionalised chalcogenoesters through lipase-catalysed transesterification reactions. Novel synthesised l-ascorbyl derivatives exhibited remarkable chain breaking and glutathione peroxidase-like activities.

Hofmeister effect of anions on calcium translocation by sarcoplasmic reticulum Ca(2+)-ATPase.

The occurrence of Hofmeister (specific ion) effects in various membrane-related physiological processes is well documented. For example the effect of anions on the transport activity of the ion pump Na(+), K(+)-ATPase has been investigated. Here we report on specific anion effects on the ATP-dependent Ca(2+) translocation by the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA). Current measurements following ATP concentration jumps on SERCA-containing vesicles adsorbed on solid supported membranes were carried out in the presence of different potassium salts. We found that monovalent anions strongly interfere with ATP-induced Ca(2+) translocation by SERCA, according to their increasing chaotropicity in the Hofmeister series. On the contrary, a significant increase in Ca(2+) translocation was observed in the presence of sulphate. We suggest that the anions can affect the conformational transition between the phosphorylated intermediates E1P and E2P of the SERCA cycle. In particular, the stabilization of the E1P conformation by chaotropic anions seems to be related to their adsorption at the enzyme/water and/or at the membrane/water interface, while the more kosmotropic species affect SERCA conformation and functionality by modifying the hydration layers of the enzyme.

Effects of solvent and alkaline earth metals on the heat-induced precipitation process of sodium caseinate.

The precipitation temperatures of sodium caseinate in H(2)O and D(2)O in the presence of Mg(2+), Ca(2+), Sr(2+) and Ba(2+) were investigated through fluorescence, turbidity and conductivity experiments. As for the ability of the divalent cations (1-17.5mM) to induce the precipitation process in H(2)O, the sequence Ba(2+) ≥ Ca(2+)>Mg(2+)>Sr(2+) was found. Remarkably, while at low salt concentrations (<10mM) precipitation temperatures (T(Ps)) were found to change significantly depending on the specific cation, at higher concentrations (>10mM) the differences among the different cations were greatly reduced. By fitting these results with a modified Jones-Dole equation, we confirmed that the less hydrated ions possess a greater capacity to induce precipitation. In D(2)O, the order of ion ability to induce caseinate precipitation was Ba(2+)>Ca(2+)>Sr(2+)>Mg(2+). The different hydrophobicity between D(2)O and H(2)O was shown to affect significantly the T(Ps) of caseinate in the presence of calcium, strontium and barium.

Organogels from a vitamin C-based surfactant.

A new double chained surfactant, 2-octyl-dodecanoyl-6-O-ascorbic acid (8ASC10), with a L-ascorbic acid unit as the polar headgroup was synthesized for the first time. The behavior of the compound in the dry solid state has been characterized through DSC, XRD, and SAXS measurements. The surfactant forms stable viscous organogels in the presence of suitable organic solvents and also water-induced organogels upon addition of water to the organogel. These mixtures show shear-thinning properties and are birefringent. The behavior and properties of the organogels have been studied through rheology, DSC, and SAXS experiments. The organogels possess the same antioxidant properties of the original L-ascorbic acid ring and can be used to solubilize and protect valuable organic molecules.

Insights into hofmeister mechanisms: anion and degassing effects on the cloud point of dioctanoylphosphatidylcholine/water systems.

Water dispersions of dioctanoylphosphatidylcholine (diC8PC) exhibit upper consolute curves. How they are affected by some salts and other additives (D2O, urea) has already been explored and the phase separation has been interpreted within the framework of the Blankschtein-Thurston-Benedek (BTB) model. This deduces the chemical potential gain in micellar growth (Deltamu) and the intermicellar interaction coefficient (C) as fitting parameters from the coexistence curves. But, the specific mechanisms that drive such phenomena have remained obscure. To identify these mechanisms, we investigate the effects of a range of anions on the cloud points of diC8PC/H2O systems and extract the phenomenological parameters of the BTB model. We show how these parameters, for micellar growth, i.e., surface, intramolecular interactions, and for interaggregate interactions, i.e., bulk solute effects, are connected to anionic polarizabilities. Nonelectrostatic (NES) quantum mechanical fluctuation (Lifshitz or dispersion) forces missing from conventional theories are then shown to regulate lyotropic Hofmeister effects, both explicitly and implicitly.

Incorporation of the sunscreen agent, octyl methoxycinnamate in a cellulosic fabric grafted with beta-cyclodextrin.

The aim of the study was to investigate the incorporation of the sunscreen agent, octyl methoxycinnamate into cyclodextrin cavities covalently bound to cloth fibres. Tencel, a cellulosic fabric, was grafted with beta-cyclodextrin molecules through reaction with monochlorotriazinyl-beta-cyclodextrin (beta-CDMCT). The finished and untreated textiles were soaked in water-methanol mixtures containing 2% (v/v) of sunscreen agent and subsequently subjected to several washing cycles. The unmodified and modified fabrics were characterized by UV spectrophotometry and thermogravimetric analysis. The level of octyl methoxycinnamate entrapped in the Tencel tissue was determined by high-performance liquid chromatography and was found to be much higher (0.0203%, w/w) for the textile functionalised with beta-CDMCT compared to the unmodified fabric (0.0025%, w/w). In addition, spectrophotometric assessment of UV transmission through the fabric samples using the Transpore test showed that the in vitro sun protection factor of the textile support was markedly enhanced (3.2-fold increase) by impregnation with octyl methoxycinnamate of the beta-CDMCT grafted textile. Hence, even after repeated washings, the beta-CD finished fabric exhibits higher sunscreen agent retention and photoprotective properties than the unmodified textile material.

Enzymatic Treatments on Tencel in Water and Microemulsion.

Tencel is a relatively new fabric, obtained from wood pulp, that looks like natural cotton. In order to be suitable for commercial purposes, Tencel must be processed to improve its qualities. In this paper we report our studies on the enzymatic defibrillation of Tencel, in which we checked the different behavior of the same set of enzymes dispersed in pure water and in a microemulsion system. Surface properties, such as scanning electron microscopy, contact angle, porosimetry, breaking load, and thickness, were determined, in order to monitor the surface modification of the fabric upon enzymatic defibrillation, and indicate that the process is more efficient and less damaging when carried out in the microemulsion medium. Furthermore, we chemically modified Tencel by attaching fluorinated chains to the fabric surface. Surface properties show that fluorination of Tencel leads to a high degree of water- and oil-repellency in the fabric. Copyright 2001 Academic Press.