Pierandrea Lo Nostro

Specific ion effects on the growth rates of Staphylococcus aureus and Pseudomonas aeruginosa

Motivated by recent advances in the physical and chemical basis of the Hofmeister effect, we measured the rate cell growth of S. aureus--a halophilic pathogenic bacterium--and of P. aeruginosa, an opportunistic pathogen, in the presence of different aqueous salt solutions at different concentrations (0.2, 0.6 and 0.9 M). Microorganism growth rates depend strongly on the kind of anion in the growth medium. In the case of S. aureus, chloride provides a favorable growth medium, while both kosmotropes (water structure makers) and chaotropes (water structure breakers) reduce the microorganism growth. In the case of P. aeruginosa, all ions affect adversely the bacterial survival. In both cases, the trends parallel the specific ion, or Hofmeister, sequences observed in a wide range of physico-chemical systems. The correspondence with specific ion effect obtained in other studies, on the activities of a DNA restriction enzyme, of horseradish peroxidase, and of Lipase A (Aspergillus niger) is particularly striking. This work provides compelling evidence for Hofmeister effects, physical chemistry in action, in these organisms.

Phase separation properties of fluorocarbons, hydrocarbons and their copolymers

Abstract In spite of their apparently similar structures, fluorocarbons (FC) and hydrocarbons (HC) possess very different properties, and their mixtures produce experimental evidences for the formation of microdomains in the solid and in the liquid state as well. Some theoretical treatments have been proposed to explain the surprising and highly non-ideal phase separation behavior of fluorocarbons/hydrocarbons mixtures, but none of them can exhaustively offer a general and realistic framework in agreement with the experimental results. The addition of semifluorinated copolymers to FC/HC mixtures enhances their mutual solubility, and leads to the formation of supramolecular structures in the liquid state.

Modification of a Cellulosic Fabric with β-Cyclodextrin for Textile Finishing Applications

Grafting of cyclodextrin (CD) molecules on suitablefabrics provides hosting cavitiesthat can include a large variety of chemicals forspecific textile finishing. In this studywe permanently grafted β-CD onto the surfaceof a cellulosic fabric, namelyTencel® according todifferent procedures. After the treatment, benzoicacid, vanillin, iodine, N,N-diethyl-m-toluamide,and dimethyl-phthalate wereloaded, by either spraying their solutionson the CD-grafted fabric, or by grafting thepreviously prepared inclusion compound onTencel®. The untreated andtreated fabrics were evaluated through scanningelectron microscopy, differential scanningcalorimetry, UV-vis spectra, X-ray diffractometry,water absorbency, breaking load loss,aroma and antimicrobial finishing tests. Our resultsindicate that the included compoundsare efficiently hosted in the CD cavities, and thefabrics surface properties are notsignificantly modified by the chemical treatments.

Drugs solubilization in ascorbyl–decanoate micellar solutions

Abstract Alkanoyl-6- O -ascorbic acid esters are obtained upon esterification of ascorbic acids primary hydroxyl groups with fatty acids. Being more hydrophobic than vitamin C, they dissolve in lipophilic media, and behave as surfactants in water, where they produce micellar aggregates or spreading monolayers, depending on the side chain length. These amphiphiles keep the same antioxidant activity of vitamin C, and can be used for solubilization and protection of hydrophobic species from oxidative degradation. In this paper we report a study on the micellar aggregates formed by decanoyl-6- O -ascorbic acid in water, through surface tension, conductivity, and solubility experiments, and on its coagels produced at low temperatures, by means of differential scanning calorimetry and scanning electron microscopy. Solubilization of some hydrophobic molecules (phenacetin, danthron, and griseofulvin) in ascorbyl–decanoate (ASC10) micelles confirms that the supramolecular assemblies significantly enhance the solubility of these drugs in the liquid phase.

Hofmeister Phenomena in Nonaqueous Media: The Solubility of Electrolytes in Ethylene Carbonate

The solubility of some potassium salts (KF, KCl, KBr, KI, KNO(3), KClO(4), KSCN, and KSeCN) in ethylene carbonate (EC) was determined at different temperatures with an inductively coupled plasma atomic emission spectrometer. From the solubility measurements, the thermodynamic parameters ΔG, ΔH, and ΔS, of solution and of solvation, were calculated. Measurements were carried out via XRD, ATR, and FTIR to determine the effect of each salt on the properties of the solvent. The open question of whether specific ion (Hofmeister) effects are restricted to hydration peculiar to water is resolved. As for water, the effects are due to solute (ion, dipolar) induced solvent structure not accounted for by electrostatic forces. Cooperative quantum mechanical forces are necessary to understand the phenomena.

Aggregates from semifluorinated n-alkanes: how incompatibility determines self-assembly

Recent work on semifluorinated alkanes (SFA) has augmented and extended our knowledge of characteristic phenomena displayed by these molecules; in solid, liquid and gel states. A review of new contributions that deal with SFA behavior in the solid phase, in monolayers, and in the liquid state is given. The experimental data confirm that the nanostructures formed are determined predominately by the incompatibility between fluorocarbons and hydrocarbons. New evidence has been presented.

Evaluation of the surfactant properties of ascorbyl palmitate sodium salt

In this paper we report on the physicochemical surface properties of ascorbyl palmitate (Asc16) and of its sodium salt (Asc16Na) with a view to their use as surfactants. Asc16Na was synthesized from ascorbyl palmitate by neutralizing the -OH groups in position 3 of the ascorbyl ring. The acid-base properties, thermal analysis and stability of Asc16Na monomers were determined. Self-assembling parameters of micellar aggregates in aqueous dispersions through critical micellar concentration (CMC) and critical micellar temperature (CMT) were measured. Asc16Na micellar dispersions efficiently solubilize poorly soluble drugs such as phenacetin and griseofulvin, and enhance their apparent solubility in aqueous environments. Stability tests showed that Asc16Na is more unstable than ascorbyl palmitate. Ascorbyl palmitate and its sodium salt are insoluble at room temperature in water, but their solubilities strongly depend on temperature, and largely increase above the CMT. Although Asc16Na is insoluble at room temperature, it is more soluble than Asc16, and its CMT significantly lowers in the undissociated acidic form. The apparent solubilities of phenacetin and griseofulvin are increased in Asc16Na aqueous solutions. The Asc16Na potential use as surfactant is restricted by its low stability in water, therefore the addition of some antioxidant species is necessary.

Adsorption Isotherms of Aqueous C12E6 and Cetyltrimethylammonium Bromide Surfactants on Solid Surfaces in the Presence of Low Molecular Weight Coadsorbents

In this work, we evaluate the effects of the low molecular weight compounds toluene, phenol, and 1-hexanol on the adsorption of two surfactants on one solid surface. The surfactants are cetyltrimethylammonium bromide (CTAB, cationic) and hexaethylene glycol monododecyl ether (C12E6, nonionic). The surface is gold, although X-ray photoelectron spectroscopic analysis reveals the presence of a large number of oxygenated sites that render the surface hydrophilic (contact angle 10 degrees). Adsorption isotherms are measured using a quartz crystal microbalance with dissipation monitoring (QCM-D). Although our measurements do not allow the determination of the morphology of the aggregates directly, we rationalize our results by referring to AFM images from the literature. On the basis of primarily the dissipative signal and on AFM studies done by others, our results are consistent with CTAB forming a patchy cylindrical structure and C12E6 likely yielding a monolayer structure. The presence of cosolutes almost doubles the mass of surface aggregates and increases the rigidness of the aggregates for CTAB, consistent with a morphological change from cylinders to flat bilayers. Part of the increase in adsorbed mass is likely due to increased surface area covered by admicelles. For C12E6, cosolutes cause small changes in the mass adsorption and essentially no change in the flexibility of surface aggregates.

Structural properties of vesicles produced from a new bipolar lipid

Abstract Symmetric vesicles are obtained from aqueous dispersions of a bipolar lipid, ( R, S )-3,25,(26)-bis(β- d -glucopyranosylthio)-1,6,23,28-tetraoxacyclotetratetracontan-2,5,24,27-tetrone (G44T), upon sonication and ultracentrifugation. Vesicles are produced also from mixed aqueous dispersions of G44T with diheptanoylphosphatidylcholine (DHPC). Scanning electron microscopy and dynamic light-scattering techniques give similar results for the vesicular diameter. The stability of these vesicles in time, temperature, and upon addition of DHPC is investigated.

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 Ca2+ translocation by the sarcoplasmic reticulum Ca2+-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 Ca2+ translocation by SERCA, according to their increasing chaotropicity in the Hofmeister series. On the contrary, a significant increase in Ca2+ 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.