Propriedades superficiais e floculação de Kluyveromyces marxianus

A floculação de leveduras e urn processo sob controlo genetico que envolve a interação entre protefnas da parede de celulas adjacentes. Assim, as propriedades superficiais das paredes celulares devem constituir urn dos factores determinantes do processo de agregação. Resultados experimentais confirmando esta hipotese tern sido descritos para estirpes de Saccharomyces. Estes estudos devem ser alargados a outros tipos de leveduras. Neste trabalho são analisadas as propriedades superficiais das paredes celulares (hidrofobicidade e potencial 1;) e sua relação com a capacidade de floculação de uma estirpe de Kluyveromyces marxianus

Use of LC-MS analysis to elucidate by-products of niacinamide transformation following in vitro skin permeation studies

Pyridine-3-carboxamide, also known as niacinamide (NIA), is used in many pharmaceutical and personal care formulations for the improvement of skin barrier function, management of acne and amelioration of the symptoms of atopic dermatitis [1-3]. The widespread use of NIA (Table I) in skin care highlights the importance of understanding the percutaneous penetration and skin distribution of this molecule [4]. Previously, we have conducted several studies that have evaluated a wide variety of NIA formulations [4, 5]

Anisotropic ferromagnetism in carbon doped zinc oxide from first-principles studies

A density functional theory study of substitutional carbon impurities in ZnO has been performed, using both the generalized gradient approximation (GGA) and a hybrid functional (HSE06) as exchange-correlation functional. It is found that the non-spinpolarized C$_\mathrm{Zn}$ impurity is under almost all conditions thermodynamically more stable than the C$_\mathrm{O}$ impurity which has a magnetic moment of $2\mu_{\mathrm{B}}$, with the exception of very O-poor and C-rich conditions. This explains the experimental difficulties in sample preparation in order to realize $d^{0}$-ferromagnetism in C-doped ZnO. From GGA calculations with large 96-atom supercells, we conclude that two C$_\mathrm{O}$-C$_\mathrm{O}$ impurities in ZnO interact ferromagnetically, but the interaction is found to be short-ranged and anisotropic, much stronger within the hexagonal $ab$-plane of wurtzite ZnO than along the c-axis. This layered ferromagnetism is attributed to the anisotropy of the dispersion of carbon impurity bands near the Fermi level for C$_{\mathrm{O}}$ impurities in ZnO. From the calculated results, we derive that a C$_{\mathrm{O}}$ concentration between 2% and 6% should be optimal to achieve $d^{0}$-ferromagnetism in C-doped ZnO.Comment: 9 pages, 7 figure

Atomic Parity Non-Conservation, Neutron Radii, and Effective Field Theories of Nuclei

Accurately calibrated effective field theories are used to compute atomic parity non-conserving (APNC) observables. Although accurately calibrated, these effective field theories predict a large spread in the neutron skin of heavy nuclei. While the neutron skin is strongly correlated to a large number of physical observables, in this contribution we focus on its impact on new physics through APNC observables. The addition of an isoscalar-isovector coupling constant to the effective Lagrangian generates a wide range of values for the neutron skin of heavy nuclei without compromising the success of the model in reproducing well constrained nuclear observables. Earlier studies have suggested that the use of isotopic ratios of APNC observables may eliminate their sensitivity to atomic structure. This leaves nuclear structure uncertainties as the main impediment for identifying physics beyond the standard model. We establish that uncertainties in the neutron skin of heavy nuclei are at present too large to measure isotopic ratios to better than the 0.1% accuracy required to test the standard model. However, we argue that such uncertainties will be significantly reduced by the upcoming measurement of the neutron radius in 208Pb at the Jefferson Laboratory.Comment: 24 pages, 6 figures, revtex4; one figure adde

Sum Rule Approach to the Isoscalar Giant Monopole Resonance in Drip Line Nuclei

Using the density-dependent Hartree-Fock approximation and Skyrme forces together with the scaling method and constrained Hartree-Fock calculations, we obtain the average energies of the isoscalar giant monopole resonance. The calculations are done along several isotopic chains from the proton to the neutron drip lines. It is found that while approaching the neutron drip line, the scaled and the constrained energies decrease and the resonance width increases. Similar but smaller effects arise near the proton drip line, although only for the lighter isotopic chains. A qualitatively good agreement is found between our sum rule description and the presently existing random phase approximation results. The ability of the semiclassical approximations of the Thomas-Fermi type, which properly describe the average energy of the isoscalar giant monopole resonance for stable nuclei, to predict average properties for nuclei near the drip lines is also analyzed. We show that when hbar corrections are included, the semiclassical estimates reproduce, on average, the quantal excitation energies of the giant monopole resonance for nuclei with extreme isospin values.Comment: 31 pages, 12 figures, revtex4; some changes in text and figure

Cell wall surface properties and flocculence of a Kluyveromyces marxianus strain

Yeast flocculation is under genetic control and is described as a cell wall interaction. This characteristic of yeast cells has been traditionally used in industrial fermentation processes. The surface characteristics of the cell walls are expected to be a determinant factor in the aggregation mechanism. Results confirming this have been reported for Saccharomyces strains. It is important to extend these studies to other genera. Among them, due to its potential industrial interest, Kluyveromyces strains must be considered. In this work are reported results relating cell wall surface properties (hydrophobicity and electrophoretic mobility) with the flocculation ability of a strain of Kluyveromyces marxianus. The effect of proteolytic enzymes, pH, salts and sugars on flocculation was also studied. The results obtained clearly demonstrate that cell wall hydrophobicity is a major determinant in the flocculation ability of the Kluyveromyces marxianus cells.Junta Nacional de Investigação Científica e Tecnológica (JNICT

Ion Pairs for Transdermal and Dermal Drug Delivery: A Review

Ion pairing is a strategy used to increase the permeation of topically applied ionised drugs. Formation occurs when the electrostatic energy of attraction between oppositely charged ions exceeds their mean thermal energy, making it possible for them to draw together and attain a critical distance. These ions then behave as a neutral species, allowing them to partition more readily into a lipid environment. Partition coefficient studies may be used to determine the potential of ions to pair and partition into an organic phase but cannot be relied upon to predict flux. Early researchers indicated that temperature, size of ions and dielectric constant of the solvent system all contributed to the formation of ion pairs. While size is important, this may be outweighed by improved lipophilicity of the counter ion due to increased length of the carbon chain. Organic counter ions are more effective than inorganic moieties in forming ion pairs. In addition to being used to increase permeation, ion pairs have been used to control and even prevent permeation of the active ingredient. They have also been used to stabilise solid lipid nanoparticle formulations. Ion pairs have been used in conjunction with permeation enhancers, and permeation enhancers have been used as counter ions in ion pairing. This review attempts to show the various ways in which ion pairs have been used in drug delivery via the skin. It also endeavours to extract and consolidate common approaches in order to inform future formulations for topical and transdermal delivery