Calcium adsorption and displacement: characterization of lipid monolayers and their interaction with membrane-active peptides/proteins

BACKGROUND: The first target of antimicrobial peptides (AMPs) is the bacterial membrane. In the case of Gram-negative bacteria this is the outer membrane (OM), the lipid composition of which is extremely asymmetric: Whereas the inner leaflet is composed of a phospholipid mixture, the outer leaflet is made up solely from lipopolysaccharides (LPSs). LPS, therefore, represents the first target of AMPs. The binding and intercalation of polycationic AMPs is driven by the number and position of negatively charged groups of the LPS. Also, proteins other than cationic AMPs can interact with LPS, e.g. leading eventually to a neutralization of the endotoxic effects of LPS. We compared different biophysical techniques to gain insight into the properties of the electrical surface potentials of lipid monolayers and aggregates composed of LPSs and various phospholipids and their interaction with peptides and proteins. RESULTS: The net negative charge calculated from the chemical structure of the phospholipid and LPS molecules is linearly correlated with the adsorption of calcium to two-dimensional lipid monolayers composed of the respective lipids. However, the ζ-potentials determined by the electrophoretic mobility of LPS aggregates can only be interpreted by assuming a dependence of the plane of shear on the number of saccharides and charged groups. Various peptides and proteins were able to displace calcium adsorbed to monolayers. CONCLUSION: To characterize the electrical properties of negatively charged phospholipids and LPSs and their electrostatic interaction with various polycationic peptides/proteins, the adsorption of calcium to and displacement from lipid monolayers is a suitable parameter. Using the calcium displacement method, the binding of peptides to monolayers can be determined even if they do not intercalate. The interpretation of ζ-potential data is difficulty for LPS aggregates, because of the complex three-dimensional structure of the LPS molecules. However, the influence of peptides/proteins on the ζ-potential can be used to characterize the underlying interaction mechanisms

The mycocidal, membrane-active complex of Cryptococcus humicola is a new type of cellobiose lipid with detergent features

AbstractThe chemical composition of the mycocidal complex (formerly known as microcin) secreted by Cryptococcus humicola was investigated by chemical, mass spectrometric and nuclear magnetic resonance methods. The results indicate that the mycocidal complex is composed of glycolipids with a highly acetylated (up to five acetyl groups) cellobiose backbone [β-D-Glcp-(1′→4)-β-D-Glcp] linked to the ω-hydroxyl group of α,ω-dihydroxy palmitate [16:0-α,ω-di-OH] with an unsubstituted carboxyl group. The acyl chain forming aglycon can be replaced by [18:0-(α,ω-di-OH)], [18:0-(α,ω-1,ω-tri-OH)], and [18:0-(α,ω-2,ω-tri-OH)]. The complex has a comparatively high surface activity; 0.5 mg/ml of it reduced the surface tension of 0.1 M NaHCO3 from 71 mN/m to 37 mN/m and interfacial tension against n-hexadecane from 39 mN/m to 10 mN/m. The critical micelle concentration of the complex at pH 4.0, determined by the fluorometric method with N-phenyl-1-naphthylamine as fluorescent probe and by the De Nouy ring method, was 2×10−5 M (taking the average molecular mass of the complex to be 750); it did not depend on the presence of 100 mM KCl and was an order of magnitude higher at pH 7.0. By fluorescence resonance energy transfer spectroscopy with N-(7-nitro-2,1,3-benzoxadiazol-4-yl)-phosphatidylethanolamine as energy donor and N-(rhodamine B sulfonyl)-phosphatidylethanolamine as energy acceptor the complex was shown to intercalate into the liposomal lipid matrix. Primary lesions caused by the complex in planar lipid bilayers were revealed as short-living current fluctuations of a broad spectrum of amplitudes. The mycocidal effect of the complex is suggested to be associated with its detergent-like properties

HISTORICAL ANALYSIS OF MESSAGE CONTENTS TO RECOMMEND ISSUES TO OPEN SOURCE SOFTWARE CONTRIBUTORS

Developers of distributed open source projects make use of issue tracker tools to coordinate their work. These tools store valuable information, maintaining a log of relevant decisions and bug solutions. Finding the appropriate issues to contribute can be hard, as the high volume of data increases contributors’ overhead. This paper shows the importance of the content of issue tracker discussions in an open source project to build a classifier to predict the participation of a contributor in an issue. To design this prediction model, we used two machine learning algorithms called Naïve Bayes and J48. We used data from the Apache Hadoop Commons project to evaluate the use of the algorithms. By applying machine learning algorithms to the ten most active contributors of this project, we achieved an average recall of 66.82% for Naïve Bayes and 53.02% using J48. We achieved 64.31% of precision and 90.27% of accuracy using J48. We also conducted an exploratory study with five contributors that took part in fewer issues and achieved 77.41% of precision, 48% of recall, and 98.84% accuracy using J48 algorithm. The results indicate that the content of comments in issues of open source projects is a relevant factor to recommend issues to contributors.Os desenvolvedores de projetos de software livre distribuídos utilizam ferramentas de acompanhamento de pendências para coordenar o seu trabalho. Essas ferramentas armazenam informações importantes, mantendo registro de decisões importantes e soluções para bugs. Decidir sobre que pendências são as mais adequadas para se contribuir pode ser difícil, uma vez que a elevada quantidade de dados aumenta a pressão sobre os desenvolvedores. Este artigo mostra a importância do conteúdo das discussões que ocorrem por meio da ferramenta de acompanhamento de pendências em um projeto de software livre para a construção de um classificador para predizer a participação de um colaborador na solução de um problema. Para projetar este modelo de predição, utilizamos dois algoritmos de aprendizagem de máquina: Naïve Bayes e J48. Utilizamos dados do projeto Apache Hadoop Commons para avaliar o uso dos algoritmos. Aplicando algoritmos de aprendizado de máquina aos dez desenvolvedores mais ativos no projeto, obtivemos uma média de recall de 66,82% para Naïve Bayes e 53,02% usando J48. Obtivemos 64,31% de precisão e 90,27% de acurácia usando o J48. Também realizamos um estudo exploratório com cinco desenvolvedores que participaram na solução de um volume menor de problemas , obtendo 77,41% de precisão, 48% de recall, e 98,84% de acurácia usando o algoritmo J48. Os resultados indicam que o conteúdo dos comentários em pendências/ problemas em projetos de software livre representam um fator relevante com base no qual recomendar pendências aos desenvolvedores que colaboram com o projeto

Nonequilibrium wetting

When a nonequilibrium growing interface in the presence of a wall is considered a nonequilibrium wetting transition may take place. This transition can be studied trough Langevin equations or discrete growth models. In the first case, the Kardar-Parisi-Zhang equation, which defines a very robust universality class for nonequilibrium moving interfaces, with a soft-wall potential is considered. While in the second, microscopic models, in the corresponding universality class, with evaporation and deposition of particles in the presence of hard-wall are studied. Equilibrium wetting is related to a particular case of the problem, it corresponds to the Edwards-Wilkinson equation with a potential in the continuum approach or to the fulfillment of detailed balance in the microscopic models. In this review we present the analytical and numerical methods used to investigate the problem and the very rich behavior that is observed with them.Comment: Review, 36 pages, 16 figure

Frequency and gender differences in the use of professional home care in late life: Findings from three German old-age cohorts

Aim: The aim of this study was to investigate the frequency of and the gender differences in the use of professional home care in Germany. Methods: We used harmonized data from three large cohort studies from Germany (“Healthy Aging: Gender-specific trajectories into the latest life”; AgeDifferent.de Platform). Data were available for 5,393 older individuals (75 years and older). Mean age was 80.2 years (SD: 4.1 years), 66.6% were female. Professional homecare outcome variables were use of outpatient nursing care, paid household assistance, and meals on wheels’ services. Logistic regression models were used, adjusting for important sociodemographic variables. Results: Altogether 5.2% of older individuals used outpatient nursing care (6.2% women and 3.2% men; p < 0.001), 24.2% used paid household assistance (26.1% women and 20.5% men; p < 0.001) and 4.4% used meals on wheels’ services (4.5% women and 4.0% men; p = 0.49). Regression analysis revealed that women had higher odds of using paid household assistance than men (OR = 1.48, 95% CI: [1.24–1.76]; p < 0.001), whereas they had lower odds of using meals on wheels’ services (OR = 0.64, 95% CI: [0.42–0.97]; p < 0.05). No statistically significant differences in using outpatient nursing care between women and men were found (OR = 1.26, 95% CI: [0.87–1.81]; p = 0.225). Further, the use of home care was mainly associated with health-related variables (e.g., stroke, Parkinson’s disease) and walking impairments. Conclusions: Our study showed that gender differences exist in using paid household assistance and in culinary dependency. For example, meals on wheels’ services are of great importance (e.g., for individuals living alone or for individuals with low social support). Gender differences were not identified regarding outpatient nursing care. Use of professional home care servicesmay contribute to maintaining autonomy and independence in old age

Exosomes Communicate Protective Messages during Oxidative Stress; Possible Role of Exosomal Shuttle RNA

BACKGROUND: Exosomes are small extracellular nanovesicles of endocytic origin that mediate different signals between cells, by surface interactions and by shuttling functional RNA from one cell to another. Exosomes are released by many cells including mast cells, dendritic cells, macrophages, epithelial cells and tumour cells. Exosomes differ compared to their donor cells, not only in size, but also in their RNA, protein and lipid composition. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we show that exosomes, released by mouse mast cells exposed to oxidative stress, differ in their mRNA content. Also, we show that these exosomes can influence the response of other cells to oxidative stress by providing recipient cells with a resistance against oxidative stress, observed as an attenuated loss of cell viability. Furthermore, Affymetrix microarray analysis revealed that the exosomal mRNA content not only differs between exosomes and donor cells, but also between exosomes derived from cells grown under different conditions; oxidative stress and normal conditions. Finally, we also show that exposure to UV-light affects the biological functions associated with exosomes released under oxidative stress. CONCLUSIONS/SIGNIFICANCE: These results argue that the exosomal shuttle of RNA is involved in cell-to-cell communication, by influencing the response of recipient cells to an external stress stimulus

The design of an office headquarters for SAMSUNG in the foreshore, Cape Town

This treatise developed through an interest in 21st century office buildings and most particularly, their impact on productivity, employee wellness and corporate culture. The conventional office of the mid-20th century disregarded employee health and well-being and was geared toward increasing productivity and production. The retrofitting of these buildings is very costly, and it is almost impossible to ensure compliance with modern-day environmental and efficiency standards to ultimately create a good office environment conducive to productivity and employee well-being. The nature of office has shifted to a more collaborative, socially interactive, open and flexible working environment because of the mobility technology offers the workplace. The current office building typology is concerned with the health and well-being of employees, active design, sustainability and environmental awareness. The treatise takes a qualitative research approach that is exploratory in nature and through careful analysis and interpretation, site constraints and informants are identified that inform the design of an office headquarters for Samsung. Pure research is based on the readings of Richard Sennett, Jane Jacobs, Stephen Kellert and Judith Heerwagen. An understanding is developed around factors that positively impact employee health and well-being in the workplace. Research determines that social interaction, human nature connectivity and the designed environment significantly impact the health and well-being of office user. Social interaction is scalable from the urban network to internal workspaces and is essential to create a seamless connection between the office environment and immediate urban context to stimulate serendipitous moments of interaction. The design of a Samsung Headquarters in Foreshore Cape Town uses Building Information Management (BIM) among other strategies to respond to its immediate environmental conditions and to create an environment conducive to the health and well-being of the office user and effectively increase productivity. The design is situated along a prominent pedestrian corridor that connects the CBD to the waterfront

Editorial iSys - Vol. 12, No. 4

A iSys – Revista Brasileira de Sistemas de Informação é uma publicação científica da Comissão Especial de Sistemas de Informação (CESI) da Sociedade Brasileira de Computação (SBC), em parceria com o Programa de Pós-Graduação em Informática (PPGI) da Universidade Federal do Estado do Rio de Janeiro (UNIRIO). A revista é distribuída em formato eletrônico através do Sistema Eletrônico de Editoração de Revistas (http://www.seer.unirio.br/index.php/isys/index).Nesta presente edição – de número 4 do Volume 12 (2019) – são publicados 1 (um) trabalho no formato versão estendida dos melhores artigos completos do III Workshop sobre Aspectos Sociais, Humanos e Econômicos de Software (WASHES 2018), além de 4 (quatro)  artigos  da  edição especial temática em “Aspectos Sociais, Humanos e Econômicos de Software