Effects of counterion valency on the damping of phonons propagating along the axial direction of liquid-crystalline DNA.

The phonon propagation and damping along the axial direction of films of aligned 40 wt % calf-thymus DNA rods are studied by inelastic x-ray scattering (IXS). The IXS spectra are analyzed with the generalized three effective eigenmode theory, from which we extract the dynamic structure factor S(Q,E) as a function of transferred energy E=variant Planck's over 2piomega, and the magnitude of the transferred wave vector Q. S(Q,E) of a DNA sample typically consists of three peaks, one central Rayleigh scattering peak, and two symmetric Stokes and anti-Stokes Brillouin side peaks.

Structural investigation of bilayers formed by 1-palmitoyl-2-oleoylphosphatidylnucleosides.

Bilayers of palmitoyl-oleoylphosphatidylnucleoside derivatives (1-palmitoyl-2-oleoyl-phosphatidyl-adenosine and 1-palmitoyl-2-oleoyl-phosphatidyl-uridine) were synthesized and investigated in the low-water content regime by a combination of neutron diffraction and Fourier transform infrared linear dichroism (LD-FTIR). Attention was focused on the modulation of structural properties operated by the presence of nucleic acid bases (either adenosine or uridine, a purine and a pyrimidine that are complementary in RNA). Base substitution causes major differences in phase behavior of the phospholipids, i.

Bioengineering of a cellulosic fabric for insecticide delivery via grafted cyclodextrin.

beta-Cyclodextrin (beta-CD) can be easily grafted onto cellulosic textiles through covalent bonds. In such a way beta-CD empty cavities provide an efficient tool for entrapping different kinds of hydrophobic molecules on the surface of the fabric and releasing them slowly in time. The capability of cyclodextrins to include hydrophobic molecules such as fragrances, antimicrobial agents, and other chemicals can be then exploited to produce new grafted textiles with peculiar and useful performances.

Surfactant aggregates hosting a photoresponsive amphiphile: structure and photoinduced conformational changes.

This paper reports the aggregational and photoresponsive properties of aqueous solutions of a cationic bolaform surfactant, where an azobenzene moiety connects two identical hydrophobic chains terminated by quaternary ammonium groups. In analogy to common surfactants, the cationic bolaform molecules form supramolecular assemblies in water, and both interfacial and associative properties can be modulated and controlled by shining the sample with the appropriate wavelength radiation. Binary and ternary (BTHA/SDS/water) systems were investigated as a function of the photosurfactant concentration, sample composition and degree of irradiation.

Nanoparticles of calcium hydroxide for wood conservation. The deacidification of the Vasa warship.

The seventeenth century Swedish warship Vasa represents a unique case in the study of ancient wrecks and a challenge for finding new methods for artifacts conservation. The presence of sulfuric acid inside the wooden structure of Vasa is one of the possible causes of chemical damage of the wood. During recent investigations, pH values below 2 were observed inside the wreck in several places.

Specific anion effects on the optical rotation of glucose and serine.

Optical activity is directly related to molecular conformation through the anisotropic polarizabilities of molecules and the refractive index of materials. L-amino acids and D-sugars are characteristic essential bioactive molecules. Since molecular recognition and enzyme activity are related to the conformation of substrates, the relevance of optical activity to biological processes is evident.

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.

Effective long-range attraction between protein molecules in solutions studied by small angle neutron scattering.

Small angle neutron scattering intensity distributions taken from cytochrome C and lysozyme protein solutions show a rising intensity at a very small wave vector Q, which can be interpreted in terms of the presence of a weak long-range attraction between protein molecules. This interaction has a range several times that of the diameter of the protein molecule, much greater than the range of the screened electrostatic repulsion. We show evidence that this long-range attraction is closely related to the type of anion present and ion concentration in the solution.

Nanoparticles of Mg(OH)2: synthesis and application to paper conservation.

We report an investigation on the effects of counterions of magnesium salts on the homogeneous phase precipitation reaction to yield nanoparticles. The results provide new parameters to guide the control of the size, monodispersity, crystallinity, and morphology of Mg(OH)(2) nanoparticles. Evidence emerged that magnesium counterions affect the size of crystallites.

Nanostructured fluids based on propylene carbonate/water mixtures.

The microstructure of aggregates formed by sodium dodecyl sulfate (SDS) and 1-pentanol in mixtures of water and a polar aprotic solvent (propylene carbonate, PC) was investigated by means of pulsed gradient spin-echo NMR, dynamic light scattering, viscosity, and conductivity measurements. PC partitions itself between micelles and aqueous bulk. The fraction of micellized propylene carbonate remains constant along PC-dilution, and the phase separation takes place when the composition of continuous phase attains the PC/water miscibility gap.

The influence of superplasticizers on the first steps of tricalcium silicate hydration studied by NMR techniques.

The influence of superplasticizer sulfonated naphthalene formaldehyde (SNF) on the hydration process of tricalcium silicate (C3S) paste was investigated by (1)H nuclear magnetic resonance spin-spin and spin lattice relaxation times. The addition of SNF superplasticizer to C3S paste clearly affects the morphology and growth rates of the hydration products, mainly by increasing the dormant period length, which lasts for several hours more than in conventional C3S hydrated paste, while reducing the acceleration period length. The relaxation data indicated that a pronounced delay occurs in the C3S hardening when sulfonated polymers are added to the makeup water.

Anion effects on calixarene monolayers: a Hofmeister series study.

Due to their amphiphilic structure, calixarenes adsorb at the air/water interface and form stable Langmuir films. We have explored the effect of salts on calix[6]- and calix[8]arene spreading isotherms at the air/water interface. A wide range of different potassium salts was used in the subphase: KCl, KI, KBr, KSCN, KNO(3), CH(3)COOK, K(2)SO(4), and K(3)PO(4).

Spectroscopic and interfacial properties of myoglobin/surfactant complexes.

The complexes of horse myoglobin (Mb) with the anionic surfactant sodium dodecyl sulfate (SDS), and with the cationic surfactants cetyltrimethylammonium chloride (CTAC) and decyltrimethylammonium bromide (DeTAB), have been studied by a combination of surface tension measurements and optical spectroscopy, including heme absorption and aromatic amino acid fluorescence. SDS interacts in a monomeric form with Mb, which suggests the existence of a specific binding site for SDS, and induces the formation of a hexacoordinated Mb heme, possibly involving the distal histidine. Fluorescence spectra display an increase of tryptophan emission.

Quasielastic and inelastic neutron scattering on hydrated calcium silicate pastes.

Using the inverse geometry spectrometer QENS at the Intense Pulsed Neutron Source of the Argonne National Laboratory, we collected quasielastic and inelastic neutron scattering spectra of hydrated tricalcium and dicalcium silicate, the main components of ordinary Portland cement. Data were obtained at different curing time, from a few hours to several months. Both the quasielastic and inelastic spectra have been analyzed at the same time according to the relaxing cage model, which is a model developed to describe the dynamics of water at supercooled temperatures.

Immobilization of a fluorescent dye in Langmuir-Blodgett films.

We immobilized a hemicyanine dye, Di-8-ANEPPS, in ordered thin films of an organic matrix, dihexadecyl phosphate (DHP), and we transferred the mixed monolayers onto solid support by the Langmuir-Blodgett technique. We used gold and quartz slides and indium tin oxide (ITO) evaporated on glass slides as substrates. The multilayers formation was confirmed by ellipsometric and contact angle measurements.

N-acetylcysteine reduces malondialdehyde levels in chronic hemodialysis patients--a pilot study.

Background: Oxidative stress has been implicated in the development of endothelial damage in hemodialysis (HD). We have assessed the effects of N-acetylcysteine (NAC), a compound with antioxidant effects, on malondialdehyde (MDA), a marker of oxidative stress on lipid peroxidation.

Methods: A clinical trial was conducted in which 24 chronic HD patients were divided into 2 groups according to gender, age, time on HD and cause of renal failure.

Proteome analysis of Escherichia coli W3110 expressing an heterologous sigma factor.

The recombinant plasmid pASK18 carries a Streptomyces DNA fragment which includes an open reading frame, designated psfS (putative sigma factor, Streptomyces), as its putative product showed a high degree of similarity with RNA polymerase sigma factors. Previous results showed that PsfS causes transcription initiation within the bgl operon promoter-silencer region in Escherichia coli K12. In this study a proteomic approach has been applied in order to perform a comparative analysis of E.

Synthesis and characterization of gels from polyallylamine and carbon dioxide as gellant.

The synthesis and characterization of a novel series of polymer gels are reported. They are formed at ambient temperatures by bubbling CO(2) through solutions of polyallylamine (PAA; a latent gellant) in several organic liquids, including aliphatic alcohols and 1-methyl-2-pyrrolidone. The stabilities of the alcohol gels, as indicated by the (irreversible) degelation temperature, T(g)(dt), were strongly dependent on the number of carbon atoms (C(n)) in the alkyl chains of the alcohol liquids.

Photosensitizer accumulation in spontaneous multidrug resistant cells: a comparative study with Rhodamine 123, Rose Bengal acetate and Photofrine.

The influence both of overexpression of multidrug transporter proteins and of phenotype changes occurring in cells developing spontaneous resistance on the accumulation of photosensitizer molecules was studied on two tumor-derived cell lines (B16, A2780) expressing the MDR-1 phenotype. Rhodamine 123, Rose Bengal acetate (a fluorogenic substrate that is restored to the native active molecule by specific enzyme activity inside cells) and Photofrin were considered. The two resistant variants accumulate Rhodamine 123 to a lesser extent than the respective wild types.

Water absorbency by wool fibers: Hofmeister effect.

Wool is a complex material, composed of cuticle and epicuticle cells, surrounded by a cell membrane complex. Wool fibers absorb moisture from air, and, once immersed in water, they take up considerable amounts of liquid. The water absorbency parameter can be determined from weight gain, according to a standard method, and used to quantify this phenomenon.

A new lipophilic fluorescent probe for interaction studies of bioactive lipopeptides with membrane models.

The new fluorescent lipophilic moiety 11-[(7-amino-4-methyl-2-oxo-2H-1-benzopyran-3-acetyl)amino]undecanoic acid (AMCA-omegaAud-OH) was introduced by SPPS at the N-terminus of the immunodominant epitope GpMBP(74-85). FRET experiments using the new fluorescent lipopeptide demonstrate that the peptide interacts with much more affinity with the membrane compared to the lipid free analogue.

Rotational dynamics of hydration water in dicalcium silicate by quasielastic neutron scattering.

Quasielastic neutron scattering (QENS) has been used to investigate the single-particle dynamics of interfacial water in dicalcium silicate (C2S)/water paste. Our previous neutron-scattering studies on interfacial water have focused attention on the translational dynamics of the center of mass of water molecules. In this paper, we have collected QENS data on a wider range of wave-vector transfer so that both translational and rotational motions of water molecules are detected.

Percolation phenomenon of calcium bis(2-ethylhexyl) sulfosuccinate water-in-oil microemulsions by conductivity and dielectric spectroscopy measurements.

The sodium counterion (Na+) of the sodium bis(2-ethylhexyl) sulfosuccinate (AOT) surfactant was exchanged with calcium Ca2+ to investigate the counterion charge effect on the structure of water in normal decane microemulsions. Ohmic conductivity and dielectric permittivity measurements were performed on samples at constant water to surfactant mole ratio [water]/[Ca(AOT)(2)]=26.6.

Dynamic scaling of quasielastic neutron scattering spectra from interfacial water.

A method for analysis of high-resolution quasielastic neutron scattering (QENS) spectra of water in porous media is proposed and applied to the case of water in hydrated tricalcium and dicalcium silicates. We plot the normalized frequency-dependent susceptibility as a function of a scaling variable [omega]/omega(p), where omega(p) is the peak position of the susceptibility function. QENS data have been scaled into a single master curve and fitted with an empirical formula proposed by Bergman to obtain three independent parameters describing the relaxation dynamics of hydration water in calcium silicates.

ESA payloads and experiments on the Foton-12 mission.

The international Foton-12 mission in September 1999 was a milestone in terms of payload mass, complexity and scientific diversity. ESA's contribution amounted to an unprecedented 240 kg--almost half of Foton's total payload. The Agency's 11 experiments covered fluid physics, biology, radiation dosimetry, materials science and meteoritics.