Laser-light scattering approach to peptide–membrane interaction

© International University Line, 2010Membrane-active peptides are becoming widely used, mainly due to their high therapeutic potential. Although the therapeutic action is characterized, the mechanisms of interaction are often unclear or controversial. In biophysical studies, non-invasive techniques are overlooked when studying the effect of peptides on membranes. Light scattering techniques, such as dynamic light scattering and static light scattering, can be used as tools to determine whether promotion of membrane aggregation in the presence of peptides and of self-peptide aggregation in solution occurs. More recently, light scattering has been used for evaluating the alteration on membrane surface charge (ζ-potential) promoted by membrane–peptide interactions. The data obtained by these techniques (either by themselves or combined with complementary experimental approaches) therefore yield valuable elucidations of membrane-active peptides’ mechanisms of action at the molecular level.This work was partially supported by the Fundação para a Ciência e Tecnologia (FCT) of the Portuguese Ministry of Science, Technology and Higher Education. M.M.D. acknowledges the grant SFRH/BD/41750/2007 from FCT

Risks of data science projects: A Delphi study

Risk is one of the most crucial components of a project. Its proper evaluation and treatment increase the chances of a project's success. This article presents the risks in Data Science projects, assessed through a study conducted with the Delphi technique, to answer the answer the question, "What are the risks of Data Science projects". The study allowed the identification of specific risks related to data science projects, however it was possible to verify that over a half of the most mentioned risks are similar to other types of IT projects. This paper describes the research from expert selection, risk identification and analysis, and the first conclusions.info:eu-repo/semantics/publishedVersio

Avaliação da capacidade de discriminação quiral da fase estacionária TRIS(3,5- Dimetilfenilcarbamato) de amilose em função do tempo de utilização da coluna cromatográfica.

A síntese de substâncias opticamente puras e a separação de enantiômeros com elevado grau de pureza enantiomérica é uma importante tarefa das indústrias químicas e farmacêuticas modernas, as quais têm intensificado o desenvolvimento de novas tecnologias devido à disponibilidade de eficientes técnicas de separação, como a cromatografia líquida de alta eficiência em fases estacionárias quirais. Os fatores levados em consideração no desenvolvimento ou utilização destas fases são: elevada disponibilidade, custos relativamente baixos, variada aplicação, estabilidade mecânica e química, elevada capacidade de adsorção e enantioseletividade. Neste trabalho, avaliou-se a capacidade de discriminação quiral da fase estacionária tris(3,5-dimetilfenilcarbamato) de amilose, sintetizada a partir de uma metodologia definida em escala analítica e em quantidade suficiente para a confecção de nove colunas cromatográficas semipreparativas. Os perfis de eluição e os parâmetros cromatográficos, resolução e fator de separação, foram avaliados após consecutivas injeções da mistura racêmica do omeprazol. Observou-se um aumento no tempo de retenção dos enantiômeros provavelmente devido a interações não específicas entre estes e o polissacarídeo não reagido e/ou a superfície da sílica não recoberta. A diminuição da capacidade de discriminação quiral da fase estacionária pode ser atribuída à perda de seletor quiral, o qual está apenas adsorvido fisicamente sobre as partículas de sílica

Influência da porosidade total do leito na cromatografia preparativa em batelada dos enantiômeros do omeprazol.

O objetivo deste trabalho foi avaliar a influência da porosidade total do leito na recuperação do enantiômero S-(-)-omeprazol em um processo cromatográfico preparativo em batelada. A variável foi calculada a partir do perfil de concentração dos enantiômeros e este obtido através da resolução numérica da equação do balanço de massa utilizando-se o modelo do equilíbrio-dispersivo. Foram avaliados dois conjuntos de dados e realizadas 50 simulações com cada um. No primeiro conjunto avaliou-se a recuperação do enantiômero de interesse em uma coluna. No segundo, a variável de desempenho foi avaliada levando-se em consideração a porosidade total média de sete colunas. Cada simulação gerou um perfil de concentração devido os dados de entrada serem aleatoriamente escolhidos pelo programa, dentro de um determinado intervalo de confiança. No primeiro conjunto de dados pode-se observar que variações da ordem de 1% na porosidade total (0,669-0,677) implicaram em uma recuperação na faixa de 51 a 100%. O valor médio dos dados forneceu uma recuperação de 92 ± 3%. Já no segundo conjunto de dados a recuperação do enantiômero de interesse variou de 10 a 100% quando consideradas variações da ordem de 3% na porosidade total (0,66-0,68). A recuperação média foi de 78 ± 10%. Diante disso, pode-se verificar que pequenas variações na porosidade total afetam significativamente a recuperação do produto

Comportamento termodinâmico da adsorção dos enantiômeros do omeprazol na fase estacionária quiral TRIS(3,5-Dimetilfenilcarbamato) de amilose.

O objetivo deste trabalho foi avaliar o comportamento termodinâmico da adsorção dos enantiômeros do omeprazol na fase estacionária quiral tris(3,5- dimetilfenilcarbamato) de amilose, sintetizada em larga escala a partir de uma metodologia definida em escala analítica. Para avaliar as constantes de Henry e os parâmetros termodinâmicos foram realizados experimentos de pulsos cromatográficos com soluções do traçador e da mistura racêmica em diferentes temperaturas e vazões da fase móvel. As isotermas de adsorção foram determinadas das curvas de ruptura obtidas com soluções da mistura racêmica em diferentes concentrações. As constantes de Henry diminuíram com a elevação da temperatura devido a uma aproximação dos picos cromatográficos. Valores negativos das variações de entalpia e entropia indicaram que é energeticamente mais favorável o soluto estar na adsorvido na fase estacionária do que em solução e que os enantiômeros encontram-se mais ordenados no estado adsorvido, respectivamente. No intervalo de concentração analisado, o modelo de isoterma de Langmuir foi bem correlacionado aos dados experimentais de equilíbrio. A capacidade de saturação da fase estacionária sintetizada é relativamente inferior à capacidade da mesma fase disponível comercialmente. A diferença está provavelmente relacionada à derivação dos grupos hidroxila da amilose e à obtenção de um derivado de uréia, durante a reação de síntese do carbamato, e ao processo de recobriment

Screening of the Potential Bioactivities of Pennyroyal (Mentha pulegium L.) Essential Oil

Increasing resistance of pathogens towards conventional antibiotics presents a major threat to public health because it reduces the effectiveness of antibiotic treatment. Mentha pulegium L., also known as pennyroyal, is an aromatic herb that belongs to the family Lamiaceae. Its essential oil has been traditionally used in medicine, aromatherapy, and cosmetics. The purpose of this work was to study the chemical composition of a pennyroyal essential oil and to evaluate their bioactivities, specifically, antioxidant, antimicrobial, anti-quorum sensing, and anti-inflammatory. A special focus was given to the antibacterial activity of the essential oil against Acinetobacter baumannii. The chemical composition of the essential oil was studied by GC-MS/GC-FID. The DPPH free radical scavenging assay and the β-carotene/linoleic acid system were used to evaluate the antioxidant properties. The antimicrobial and anti-quorum sensing activities were evaluated by disk diffusion assays and complemented with optical microscopy observations. The results showed that pulegone was the major compound (88.64%) of the pennyroyal essential oil. Regarding the antimicrobial activity, the action against Acinetobacter baumannii stands out, which, together with the capacity of the essential oil to inhibit the quorum sensing mechanisms, may suggest the use of the pennyroyal essential oil to further develop surface disinfectants for hospitals.info:eu-repo/semantics/publishedVersio

Translocating the blood-brain barrier using electrostatics

Copyright © 2012 Ribeiro,Domingues, Freire,Santos and Castanho. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.Mammalian cell membranes regulate homeostasis, protein activity, and cell signaling. The charge at the membrane surface has been correlated with these key events. Although mammalian cells are known to be slightly anionic, quantitative information on the membrane charge and the importance of electrostatic interactions in pharmacokinetics and pharmacodynamics remain elusive. Recently, we reported for the first time that brain endothelial cells (EC) are more negatively charged than human umbilical cord cells, using zeta-potential measurements by dynamic light scattering. Here, we hypothesize that anionicity is a key feature of the blood-brain barrier (BBB) and contributes to select which compounds cross into the brain. For the sake of comparison, we also studied the membrane surface charge of blood components—red blood cells (RBC), platelets, and peripheral blood mononuclear cells (PBMC).To further quantitatively correlate the negative zeta-potential values with membrane charge density, model membranes with different percentages of anionic lipids were also evaluated. From all the cells tested, brain cell membranes are the most anionic and those having their lipids mostly exposed, which explains why lipophilic cationic compounds are more prone to cross the blood-brain barrier.Fundação para a Ciência e Tecnologia — Ministério da Educação e Ciência (FCT-MEC, Portugal) is acknowledged for funding (including fellowships SFRH/BD/42158/2007 to Marta M.B. Ribeiro, SFRH/BD/41750/2007 to Marco M. Domingues and SFRH/BD/70423/2010 to João M. Freire) and project PTDC/QUI-BIQ/119509/2010. Marie Curie Industry-Academia Partnerships and Pathways (European Commission) is also acknowledged for funding (FP7-PEOPLE-2007-3-1-IAPP, Project 230654)

An open and parallel multiresolution framework using block-based adaptive grids

A numerical approach for solving evolutionary partial differential equations in two and three space dimensions on block-based adaptive grids is presented. The numerical discretization is based on high-order, central finite-differences and explicit time integration. Grid refinement and coarsening are triggered by multiresolution analysis, i.e. thresholding of wavelet coefficients, which allow controlling the precision of the adaptive approximation of the solution with respect to uniform grid computations. The implementation of the scheme is fully parallel using MPI with a hybrid data structure. Load balancing relies on space filling curves techniques. Validation tests for 2D advection equations allow to assess the precision and performance of the developed code. Computations of the compressible Navier-Stokes equations for a temporally developing 2D mixing layer illustrate the properties of the code for nonlinear multi-scale problems. The code is open source

SAMplus: adaptive optics at optical wavelengths for SOAR

Adaptive Optics (AO) is an innovative technique that substantially improves the optical performance of ground-based telescopes. The SOAR Adaptive Module (SAM) is a laser-assisted AO instrument, designed to compensate ground-layer atmospheric turbulence in near-IR and visible wavelengths over a large Field of View. Here we detail our proposal to upgrade SAM, dubbed SAMplus, that is focused on enhancing its performance in visible wavelengths and increasing the instrument reliability. As an illustration, for a seeing of 0.62 arcsec at 500 nm and a typical turbulence profile, current SAM improves the PSF FWHM to 0.40 arcsec, and with the upgrade we expect to deliver images with a FWHM of $\approx0.34$ arcsec -- up to 0.23 arcsec FWHM PSF under good seeing conditions. Such capabilities will be fully integrated with the latest SAM instruments, putting SOAR in an unique position as observatory facility.Comment: To appear in Proc. SPIE 10703 (Ground-based and Airborne Instrumentation for Astronomy VII; SPIEastro18

Pullulan–Apple Fiber Biocomposite Films: Optical, Mechanical, Barrier, Antioxidant and Antibacterial Properties

More than 150 million tons of synthetic plastics are produced worldwide from petrochemical-based materials, many of these plastics being used to produce single-use consumer products like food packaging. The main goal of this work was to research the production and characterization of pullulan–apple fiber biocomposite films as a new food packaging material. The optical, mechanical, and barrier properties of the developed biocomposite films were evaluated. Furthermore, the antioxidant and antibacterial activities of the biocomposite films were additionally studied. The results show that the Tensile Index and Elastic Modulus of the pullulan–apple fiber films were significantly higher (p-value < 0.05) when compared to the pullulan films. Regarding the water vapor permeability, no significant differences (p-value < 0.05) were observed in water vapor transmission rate (WVTR) when the apple fiber was incorporated into the biocomposite films. A significant increase (p-value < 0.05) of water contact angle in both sides of the films was observed when the apple fiber was incorporated into pullulan, indicating an increase in the hydrophobicity of the developed biocomposite films. It is worth noting the hydrophobicity of the (rough) upper side of the pullulan–apple fiber films, which present a water contact angle of 109.75°. It was possible to verify the microbial growth inhibition around the pullulan–apple fiber films for all the tested bacteria.info:eu-repo/semantics/publishedVersio