Publications

Abstract The innate immunity factor lactoferrin harbours two antimicrobial moieties, lactoferricin and lactoferrampin, situated in close proximity in the NI domain of the molecule. Most likely they cooperate in many of the beneficial activities of lactoferrin. To investigate whether chimerization of both peptides forms a functional unit we designed a chimerical structure containing lactoferricin amino acids 17-30 and lactoferrampin amino acids 265-284. The bactericidal activity of this LFchimera was found to be drastically stronger than that of the constituent peptides, as was demonstrated by the need for lower dose, shorter incubation time and less ionic strength dependency. Likewise, strongly enhanced interaction with negatively charged model membranes was found for the LFchimera relative to the constituent peptides. Thus, chimerization of the two antimicrobial peptides resembling their structural orientation in the native molecule strikingly improves their biological activity.

Abstract A thermochemical and thermophysical study has been carried out for crystalline barbital [5,5'-diethyl-barbituric acid]. The thermochemical study was made by static bomb combustion calorimetry, from which the standard (p degrees = 0.1 MPa) molar enthalpy of formation of the crystalline barbital, at T = 298.15 K, was derived as -(753.0 +/- 1.8) kJ . mol(-1). The thermophysical study was made by differential scanning calorimetry over the temperature interval (265 to 470) K. A solid-solid phase transition was found at T = 413.3 K. The vapour pressures of the crystalline barbital were measured at several temperatures between T = (355 and 377) K, by the Knudsen mass-loss effusion technique, from which the standard molar enthalpy of sublimation, at T = 298.15 K was derived as (117.3 +/- 0.6) kJ . mol(-1). The combination of the experimental results yielded the standard molar enthalpy of formation of barbital in the gaseous phase, at T = 298.15 K, as -(635.8 +/- 1.9) kJ . mol(-1). This value is compared and discussed with our theoretical calculations by several methods (Gaussian-n theories G2 and G3, complete basis set CBS-QB3, density functional B3P86 and B3LYP) by means of atomization and isodesmic reaction schemes.

Abstract The present work reports an experimental thermochemical study supported by state of the art calculations of two heterocyclic compounds containing oxygen in the ring: xanthone and tetrahydro-gamma-pyrone. The standard (pA(0)A = 0.1 MPa) molar enthalpies of formation in the condensed phase, at T = 298.15 K, were derived from the measurements of the standard molar energies of combustion in oxygen atmosphere, using a static bomb calorimeter. The standard molar enthalpies of sublimation or vaporization, at T = 298.15 K, of the title compounds were obtained from Calvet microcalorimetry measurements. These values were used to derive the standard enthalpies of formation of the compounds in the gas-phase at the same temperature, which were compared with estimated data from G3(MP2)//B3LYP computations.

Abstract The molecular stability of thioxanthene, a key species from which very important compounds with industrial relevance are derived, has been studied by a combination of several experimental techniques and computational approaches, The standard (p(o) = 0.1 MPa) molar enthalpy of formation of crystalline thioxanthene (117.4 +/- 4.1 kJ . mol(-1)) was determined from the experimental standard molar energy of combustion, in oxygen, measured by rotating-bomb combustion calorimetry at T = 298.15 K. The enthalpy of sublimation was determined by a direct method, using the vacuum drop microcalorimetric technique, and also by an indirect method, using a static apparatus, where the vapor pressures at different temperatures were measured. The latter technique was used for both crystalline and undercooled liquid samples, and the phase diagram of thioxanthene near the triple point was obtained (triple point coordinates T = 402.71 K and p = 144.7 Pa). From the two methods, a mean value for the standard (p(o) = 0.1 MPa) molar enthalpy of sublimation, at T = 298.15 K (101.3 +/- 0.8 kJ . mol(-1)), was derived. From the latter value and from the enthalpy of formation of the solid, the standard (p(o) = 0.1 MPa) enthalpy of formation of gaseous thioxanthene was calculated as 218.7 +/- 4.2 kJ . mol(-1). Standard ab initio molecular orbital calculations were performed using the G3(MP2)//B3LYP composite procedure and several homodesmotic reactions in order to derive the standard molar enthalpy of formation of thioxanthene. The ab initio results are in excellent agreement with the experimental data.

Abstract The structure and temperature behaviour of the DNA+dipalmitoylphosphatidylcholine (DPPC) bilayer as a function of ZnCl(2) concentration were examined using differential scanning calorimetry (DSC), small-angle neutron scattering (SANS) and small-angle X-ray diffraction (SAXD). Experiments revealed the coexistence of two lamellar phases in the mixture: the L(PC) phase, formed due to Zn(2+) binding to the DPPC bilayers, and the condensed lamellar phase L(DNA+PC) with DNA strands packed between the DPPC bilayers. With increasing concentration of zinc, the temperature of the gel - liquid-crystal phase transition of DPPC increases in both phases, and the volume fraction of LDNA+PC phase decreases. In the gel state (at 20 degrees C), the repeat distance of LDNA+PC phase is constant, d(DNA+PC) similar to 8.3 nm, up to 20 mmol/l of ZnCl(2), and increases for higher concentrations of the salt. The periodicity of the L(PC) lamellar phase decreases substantially with the increasing concentration of the salt in the mixture. In the liquid-crystalline state, concentrations above 20 mmol/l ZnCl(2) promote the dissolution of the LDNA+PC phase into DPPC + Zn(2+) unilamellar vesicles and DNA is neutralized by Zn(2+) ions. The screening of Zn(2+) charge and the formation of a diffuse double layer due to increasing ionic strength of solution are responsible for the observed changes.

Abstract One of the possible approaches for the development of novel solid-phase microextraction (SPME)fibers is the physical deposition of porous materials Oil to a support using high-temperature epoxy glue. However, a major drawback arises from decomposition of epoxy glue at temperatures below 300 degrees C and instability in some organic solvents. This limitation motivated us to explore the possibility of replacing the epoxy glue with a sol-gel film, thermally more stable and resistant to organic solvents. We found that functionalised silica particles could be successfully attached to a robust Ni-Ti wire by using a UV-curable sol-gel film. The particles were found to be more important than the sol-gel layer during the microextraction process, as shown by competitive extraction trials and by the different extraction profiles observed with differently functionalised particles. If a quality control microscopic-check aiming at the rejection of fibers exhibiting unacceptably low particle load was conducted, acceptable (6-14%) reproducibility of preparation of C(18)-silica fibers was observed, and a strong indication of the durability of the fibers was also obtained. A cyclohexyldiol-silica fiber was used, as a simple example of applicability, for the successful determination of benzaldehyde. acetophenone and dimethyl phenol at trace level in spiked tap water. Recoveries: 95-109%; limits of detection: 2-7 mu g/L; no competition effects within the studied range (<= 125 mu g/L).

Abstract Marine organisms are known to accumulate arsenic (As) in The range of 1-100 mg kg(-1) from their environment and food sources. The majority of arsenic is present as organoarsenic compounds, metabolized from inorganic arsenic present in seawater or accumulaled from food sources such as algae or other fish. The aim of This study was to evaluate total arsenic content in The muscle of eight fish species, three cephalopods, and one crustacean consumed in Portugal. The measurement of total arsenic (10 individuals of each species) was carried out by EDXRF (Energy Dispersive X-Ray Fluorescence Method). The highest concentrations were found in Norway lobster (30.3 +/- 8.7 mg kg(-1) wet weight), followed by common octopus (25.9 +/- 8.4 mg kg(-1) wet weight). Within fish species, wild gilthead sea bream, anglerfish, and megrim species presented values around 12 mg kg,(-1) and in the others the average was lower than 10 mg kg(-1). Taking into consideration the tolerable daily intake recommended by the World Health Organization (WHO; 0.05 mg As kg(-1) body weight) the obtained results of total arsenic in The studied species do not represent a bazard for buman consumption.

Abstract A challenge that faces the footwear market is the improvement of casual shoe comfort, being shock absorption one of the most significant properties for comfort. However, the methodologies available for the quantification of the shock absorption properties in materials for footwear applications are limited. With this work, an evaluation methodology of the shock absorption properties of rubber materials is proposed and the relationship between different test methods is established. Eight different commercial compact heeled rubber materials at six different thicknesses were prepared and characterized according to their physical and impact absorption properties. From the experimental values, the following correlations were defined: energy compression/hardness and energy compression/maximum deceleration. Shock absorption prediction curves were also determined from the experimental maximum deceleration values. Results present an excellent tool for industrial applications since they allow correlation of shock absorption properties and heel thickness, and also to predict the contribution of rubber material composition to the final product shock absorption properties.

Abstract This study intends to present some further research in polymer-dispersed liquid crystal (PDLC) systems [1]. These PDLC type cells were produced based on a low-cost commercial polymer (PVC) and liquid crystal E48 (Merck), using a modified solvent preparation method (SIPS). These cells were characterized electro-optically and by low frequency dielectric relaxation (20 Hz to 1 MHz) experiments. Results are encouraging; the prepared composites show regular microstructures and optical transmittance changes induced by the electric field, introducing an alternative way of producing low-cost PDLC electro-optical cells.