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The effect of choline addition on the salt-induced super activity of horseradish peroxide (HRP) is investigated. HRP is presented as an efficient H2O scavenger, and choline is the precursor of glucine betaine, a strong osmoprotectant molecule.

Ordered mesoporous materials (OMMs) have a pore size suitable to host proteins. Previous works have shown how to tune the amount of adsorbed protein by changing pH or ionic strength of the adsorbing solution. Here we investigated the adsorption of lysozyme on a functionalized SBA-15 (SBA-15-NH(2)) as a function of added salts. For the first time, it was ascertained that the amount of adsorbed protein follows a reversed Hofmeister series for anions (sodium salts), SCN(-) > ClO(4)(-) > Br(-) > NO(3)(-) > Cl(-) > SO(4)(2-), whereas for cations (chloride salts) the sequence was Na(+) > Li(+) > K(+) > Cs(+). These findings not only demonstrate a specific effect of the Na(+) SCN(-) ion pair in favoring the adsorption at a solid surface but confirm also the role of the biologically important sodium ions. In addition, the process was found to be more effective at 0.2 M than at 0.8 M, thus indicating that adsorption also depends on the added salt concentration.

Here, monoolein-based nanoparticles (NPs), obtained through fragmentation of bulk liquid crystalline phases, and stabilized by two different emulsifiers, namely, Pluronic F127 (PF127) and lauroylcholine chloride (LCh), are investigated for structural features and for short-term in vitro cytotoxicity. Depending on the emulsifiers, different morphologies of the lipid NPs (cubosomes and liposomes) are obtained, as demonstrated by cryo-TEM images. Although NPs offer many advantages in medical applications and various chemicals used for their preparation are under investigation, so far there are no standardized procedures to evaluate cell biocompatibility. Two different protocols to evaluate the impact of these lipid NPs on biological systems are presented. Results show that nanoparticles stabilized by PF127 (cubosomes) display a relevant toxicity toward different cell lines, whereas those stabilized by LCh (liposomes) affect cell viability at a much lesser extent.

The phase diagram sodium bis(2-ethylhexyl) sulfosuccinate (NaAOT)/water/1-butyl-3-methylimidazolium tetrafluoborate (bmimBF(4)), a polar room temperature ionic liquid, is explored through optical microscopy in polarized light, SAXRD and NMR PGSTE techniques. The analysis of SAXRD and self-diffusion data reveals that the bmim(+) cation is strongly adsorbed at the interface. Data are accounted for by Hill's model for cooperative binding. The overall process is described as a comicellization of AOT(-) and bmim(+) involving roughly two cations for AOT(-) ion. The bmim(+) is severely involved in the structural arrangement of the interface. Indeed, a huge modification of the interfacial geometry resulting in the occurrence of micelles having positive curvature is inferred from the analysis of the self-diffusion coefficients. The analysis of the water diffusion data in the L(1) phase (according to the effective cell model) allows one to exclude the presence of oblate and/or discoid micelles. Finally, the study of the oil diffusion in samples doped with p-xylene permits one to assess furthermore not only the formation of AOT aggregates of the oil-in-water type but also the occurrence of dynamic percolation phenomena.

The entrapment of AMP, GMP, CMP, and UMP nucleotides along with two different AMP-based nucleolipids (hydrophobically functionalized nucleotides) inside the liquid crystalline phases of the monoolein/water system is investigated through optical microscopy, small-angle X-ray diffraction (SAXRD), and nuclear magnetic resonance (NMR) techniques. As ascertained mainly through (31)P NMR experiments, when included within the cubic phase, the various nucleotides undergo a slow hydrolysis of the sugar-phosphate ester bond, induced by specific interactions at the monoolein-water interface. Upon aging, the degradation of the nucleotides causes a cubic-to-hexagonal phase transition. Differently, neither hydrolysis nor alterations of the monoolein self-assembly are observed when the nucleotides are included as lipid derivatives within the cubic liquid crystalline phase. A model that explains both the hydrolysis and the consequent phase transition is presented.

Aqueous dispersions of the phospholipid dioctanoylphosphatidylcholine (diC 8PC) phase-separate below a cloud-point temperature, depending on lipid concentration. The lower phase is viscous and rich in lipid. The structure and dynamics of this system were explored via cryo-transmission electron microscopy (cryo-TEM), small-angle X-ray scattering (SAXS), and NMR. The lower phase comprises a highly interconnected tridimensional network of wormlike micelles. A molecular mechanism for the phase separation is suggested.

The present work shows that salt anions affect the activity of Pseudomonas cepacia lipase both in aqueous and in nonaqueous media (NAM) according to a Hofmeister series. The biocatalytic assay in water was the hydrolysis of p-nitrophenyl acetate, whereas the esterification between 1-hexyl-beta-D-galactopyranoside and palmitic acid was followed in an organic solvent. The solid lipase preparations to be used in NAM were obtained through lyophilization in the presence of concentrated solutions of Hofmeister salts (Na2SO4, NaH2PO4/Na2HPO4, NaCl, NaBr, NaI, NaSCN). Salts affect enzyme activity in organic media through two mechanisms: (1) enzyme protection during lyophilization; (2) enzyme activation during the reaction. At least in our case, the latter seems to be more important than the former. The decrease of the activation energy caused by the stabilization of the transition state due to "kosmotropic" anions might be the driving force of enzyme activation. According to the most recent findings, dispersion forces may be responsible of specific anion enzyme activation/deactivation in NAM.

The effects of weak and strong electrolytes on the enzymatic activity of Candida rugosa lipase are explored. Weak electrolytes, used as buffers, set the pH, while strong electrolytes regulate the ionic strength. The interplay between pH and ionic strength has been assumed to be the determinant of enzymatic activity. In experiments that probe activities by varying these parameters, there has been little attention focused on the role of specific electrolyte effects. Here we show that both buffers and the choice of background electrolyte ion strongly affect the enzymatic activity of Candida rugosa lipase. The effects here shown are dramatic at high salt concentration; indeed, a 2 M concentration of NaSCN is able to fully inactivate the lipase. By contrast, Na2SO4 acts generally as an activator, whereas NaCl shows a quasi-neutral behavior. Such specific ion effects are well-known and are classified among the "Hofmeister effects". However, there has been little awareness of them, or of their potential for optimization of activities in the enzyme community. Rather than the effects per se, the focus here is on their origin. New insights into mechanism are proposed.

Due to its potential relevance as a fully biocompatible formulation useful in cosmetic, food, and pharmaceutical applications, the glycerol trioleate/sodium oleate/water ternary system was investigated via optical microscopy and NMR methods. The ternary diagram is dominated by monophasic and biphasic regions where a lamellar phase coexists with different isotropic phases. A broad emulsion region, characterized by small oil droplets dispersed within the lamellar phase, extends from the center toward the water corner of the diagram. Information on the inner structure of these emulsion-like samples is supplied by modeling water and oil NMR self-diffusion data. Sizing of oil droplets was provided at different storage times. A highly polydisperse log-normal distribution was observed. The presence of the liquid crystalline phase is called into play for the negligible differences found in the droplets size distribution upon samples aging. Indeed, samples within this region stored at 25 degrees C did not show phase separation after several months from their preparation.

The effect of electrolytes on pH measurements via glass electrodes is explored with solutions buffered at pH 7 (phosphate and cacodylate). Salt and buffer concentrations are varied. Direct and reverse Hofmeister effects are observed. The phenomena are significant for salt concentrations above 0.1 M and for buffer concentrations below 20 mM. Changes in measured pH show up most strongly with anions. They can be related to the usual physicochemical parameters (anion molar volumes, molar refractivity, and surface tensions) that are characteristic of Hofmeister series. They correlate strongly with anionic excess polarizabilities; this suggests the involvement of non-electrostatic, or dispersion, forces acting on ions. These forces contribute to ionic adsorption at the glass electrode surface, and to the liquid junction potential.

The specific activity of lipase A (Aspergillus niger) toward the hydrolysis of p-nitrophenyl acetate (p-NPA) is shown to increase as a result of sodium salt addition according to specific ion effects of the Hofmeister series. This shows explicitly that the Hofmeister effect is due to the different specific interactions between anions and the enzymatic surface.