Publications

Abstract Lactoferrin is a glycoprotein with two globular lobes, each having two domains. Since the discovery of its antimicrobial properties, efforts have been made to find peptides derived from this protein showing antimicrobial properties. Most peptides initially studied were derived from Lactoferricin B, obtained from the protein by digestion with pepsin. More recently, a new family of antimicrobial peptides (AMPs) derived from Lactoferrin was discovered by Bolcher et al, and named Lactoferrampin (LFampin). The original sequence of LFampin contained residues 268 - 284 from the N1 domain of Lactoferrin. From this peptide, the Bolscher's group synthesized a collection of peptides obtained by extension and / or truncation at the C or N-terminal sides, in order to unravel the main structural features responsible for antimicrobial action. Here, we present results for three of these peptides, namely LFampin 265 - 284, LFampin 265 - 280, and LFampin 270 - 284. The peptides were tested against bacteria (E. coli and S. sanguinis), fungi (C. albicans), and model membranes of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dimyristoyl-sn-glycero- 3-[phospho-rac-(1-glycerol)] (DMPG), and their mixtures at a ratio of 3 : 1 (DMPC : DMPG (3 : 1)). The ability to adopt a helical conformation was followed by a circular dichroism (CD), and the perturbation of the gel to the liquid-crystalline phase transition of the membrane was characterized by differential scanning calorimetry (DSC). Distinct behavior was observed in the three peptides, both from the microbiology and model membrane studies, with the biophysical results showing excellent correlation with the microbiology activity studies. LFampin 265 - 284 was the most active peptide toward the tested microorganisms, and in the biophysical studies it showed the highest ability to form an α-helix and the strongest interaction with model membranes, followed by LFampin 265 - 280. LFampin 270 - 284 was inactive, showing marginal secondary structure and no interaction with the pathogen model membranes.

Abstract In the title molecule, C24H14N2, the exterior C-C-C angle of the naphthalene ring system involving the two phenyl-substituted C atoms is 126.06 (11)degrees and the dihedral angles between the mean plane of the naphthalene ring system and those of the benzene rings are 66.63 (5) and 67.89 (5)degrees. In the crystal, molecules are linked into a ladders by four weak C-H center dot center dot center dot pi interactions.

Abstract Three kappa/iota-hybrid carrageenan polysaccharides with distinct molecular mass and content of iota-carrageenan disaccharide units were isolated from Mastocarpus stellatus seaweeds. The viscoelastic and thermal properties of 2 wt% kappa/iota-hybrid carrageenan solutions with ionic strength tuned by the addition of NaCl salt were studied by means of theological tests and differential scanning calorimetry (DSC). All solutions form a gel upon cooling. The gel elasticity decreases with the content in iota-carrageenan disaccharide units, and does not correspond to the additive elasticity of a iota- and a kappa-carrageenan networks. The highest gel elasticity is obtained with the lowest molecular mass. In 0.1 M NaCl, two gelling processes are evidenced. The first increase in solution viscosity upon cooling coincides with a thermal transition process, which is assigned to a coil-to-helix conformational transition. The transition depends on both molecular mass distribution and chemical structure. The same dependencies are observed for the gel melting behaviour as all theological and thermal processes determined are shifted to higher temperature with decreased molecular mass or increased content in iota-carrageenan disaccharide units.

Abstract In this work, the phytoremediation potential of metalaxyl, a commonly used persistent, mobile and leachy fungicide, by Solanum nigrum L plants was studied. The study revealed that this plant species can be used as an excellent metalaxyl phytoremediation tool, thus providing a cost effective and environmentally friendly clean technology for the decontamination of sites and effluents. As it can be sowed directly in the remediation site, is able to complete its life cycle without suffering major stress. Because it accumulates high amounts of the fungicide in the aboveground tissues, enables its concentration and proper disposal by cutting off the corresponding plant part. The study also suggests that the tolerance to metalaxyl is due to a suitable antioxidant response comprising proline accumulation and guaiacol peroxidase and glutathione-S-transferase enhanced activities, that reduce oxidative damage to the plant organs.

Abstract The monocyclic nonsubstituted pyrones were studied computationally using state-of-the-art ab initio composite computational techniques Combination of the accurate energies so obtained with conveniently chosen isodesmic or homodesmotic chemical reactions lead to very confident predictions of their corresponding standard enthalpy of formation The internal consistency of the results obtained from a vast number of independent chemical schemes serves as a further support of the quality of our results which are thus proposed to establish the energetics of alpha-pyrone and gamma-pyrone

Abstract A fluorescent derivatization reaction for Diltiazem drug quantification based on the condensation reaction of citric or malonic acid with acetic anhydride, catalyzed by the tertiary amine group of Diltiazem, was developed. Excitation emission matrices (EEMs) of fluorescence of the pure solvent (ethanol), standard and sample solutions following a standard addition methodology were analysed by PARAFAC based methods (PARAFAC, PARAFAC2 and PARALIND) to obtain robust calibration methodologies. The quantification results of the sample were compared with the official US Pharmacopeia high performance liquid chromatography-ultraviolet method (USP HPLC-UV). Although the experimental sets of EEM show linearity deviations all the PARAFAC based methods allow correct robust estimation of Diltiazem concentration in pharmaceutical formulations. The closest results were: derivatization with citric acid and PARAFAC2 six components non-negativity constraint model with a detection limit of 0.088 ppm; and, derivatization with malonic acid and PARAFAC six components non-negativity constraint model with a detection limit of 0.066 ppm for the malonic acid was observed. The simultaneous utilization of the three PARAFAC methods gives further information about the intrinsic structure of the data sets under analysis, i.e., it works as an efficient diagnostic tool for the existence of non-linearity and colinearity.

Abstract Based on the strong interaction of noble metal particles with the sulphur atoms of thiophene derivatives, platinum nanoparticles (Pt-NPs)-dispersed poly(3-methylthiophene) (P{3-MeTh}) thin films have been successfully prepared. Evidence of the Pt-NPs confinement in the polymer was provided by the electrocatalytic activity of the modified electrodes towards the dissolved oxygen reduction reaction. The efficient immobilization by self-assembly of thiolated oligonucleotides on the embedded Pt-NPs could be monitored by electrochemical quartz crystal microbalance (EQCM) as well as the subsequent hybridization with the complementary sequence. The good conducting properties and high surface area of P(3-MeTh)/Pt-NPs modified electrodes also allowed the detection of both processes by cyclic voltammetry.

Abstract This paper describes a simple apparatus we have developed for determining elastic properties of materials. The easily constructed system may be used to measure the elongation or compression of a sample to which a succession of loads is applied. This allows stress-strain curves to be plotted and analyzed. We describe the construction and use of the apparatus and present some sample data. © 2011 American Association of Physics Teachers.

Abstract Taking advantage of the spontaneous deposition of noble metals on polymers containing sulphur, the inclusion of gold and platinum in poly(3-methylthiophene) and poly(3,4-ehylenedioxythiophene) (PEDOTh) layers, achieved by immersion of the polymer into the metal nanoparticles suspension, is reported in the present work. Platinum and gold nanoparticles (NPs), with diameters between 3 and 17 nm, have been prepared from colloidal methods (citrate or borohydride reduction in the presence of citrate capping agent) and characterized by transmission electron microscopy, ultraviolet-visible spectrophotometry and X-ray diffraction (XRD). The electropolymerization was carried out under potentiostatic and potentiodynamic conditions, imparting distinct morphologies, as revealed by atomic force microscopy. After polymer films immersion in the colloidal solutions, evidence of the NPs confinement and distribution was provided by XRD analysis and scanning electron microscopy. For thin layers, the quantity of attached metal NPs could be estimated from quartz crystal microbalance data collected throughout the films immersion. The influence of the polymer type and morphology, NPs nature, size and incorporated amount on the electrocatalytic activity of the so-prepared modified electrodes towards the hydrazine oxidation, in phosphate buffer solution, has been investigated by cyclic voltammetry. The results clearly show the superior properties of potentiodynamically prepared PEDOTh films attaching very small (3 nm) freshly prepared Pt-NPs.

Abstract The preparation of gold nanoparticles (Au-NPs) displaying specific shape, size and surface crystallographic domains has been investigated aiming to clarify the effect of the surface crystallographic orientation, of the synthesised nanoparticles, and surfactant influence on the electrochemical response of the ITO/Au-NPs modified electrodes. Polymorphic and nanorod-shaped Au-NPs have been obtained using distinct synthetic procedures in the presence of cetyltrimethylammonium bromide (CTAB), through seed-mediated growth methods, displaying distinct surface crystallographic domains confirmed by transmission electron microscopy, X-ray diffraction analysis and under potential deposition (UPD) of lead. The nanoparticles have been physically immobilised by casting on indium tin oxide (ITO) surfaces and the electrocatalytic activity of the Au-NPs evaluated using the ascorbic acid (AA) oxidation reaction, by cyclic voltammetry. The polymorphic and distinct surface crystallographic orientations of the Au-NPs were reflected in an irreproducible electrochemical response. Using gold nanorods comprising (1 1 1) and (1 1 0) facets and gold nanocubes consisting of faces displaying (1 0 0) surface domains, by contrasting the behaviour of CTAB-stabilised and clean particles, it has been possible to verify that the distinct voltammetric results are due to the exposure of specific crystallographic orientations owing to dissimilar interaction strength of CAB with those facets.