Assessing protein stability of the dimeric DNA-binding domain of E2 human papillomavirus 18 with molecular dynamics

The objective of this study is to understand the structural flexibility and curvature of the E2 protein of human papillomavirus type 18 using molecular dynamics (6 ns). E2 is required for viral DNA replication and its disruption could be an anti-viral strategy. E2 is a dimer, with each monomer folding into a stable open-faced β-sandwich. We calculated the mobility of the E2 dimer and found that it was asymmetric. These different mobilities of E2 monomers suggest that drugs or vaccines could be targeted to the interface between the two monomers.

Networks in Argentine agriculture: a multiple-case study approach

Argentina is among the four largest producers of soybeans, sunflower, corn, and wheat, among other agricultural products. Institutional and policy changes during the 1990s fostered the development of Argentine agriculture and the introduction of innovative process and product technologies (no-till, agrochemicals, GMO, GPS) and new investments in modern, large-scale sunflower and soybean processing plants. In addition to technological changes, a "quiet revolution" occurred in the way agricultural production was carried out and organized: from self-production or ownership agriculture to a contract-based agriculture. The objective of this paper is to explore and describe the emergence of networks in the Argentine crop production sector. The paper presents and describes four cases that currently represent about 50% of total grain and oilseed production in Argentina: "informal hybrid form", "agricultural trust fund", "investor-oriented corporate structure", and "network of networks". In all cases, hybrid forms involve a group of actors linked by common objectives, mainly to gain scale, share resources, and improve the profitability of the business. Informal contracts seem to be the most common way of organizing the agriculture process, but using short-term contracts and sequential interfirm collaboration. Networks of networks involve long-term relationships and social development, and reciprocal interfirm collaboration. Agricultural trust fund and investor-oriented corporate structures have combined interfirm collaboration and medium-term relationships. These organizational forms are highly flexible and show a great capacity to adapt to challenges; they are competitive because they enjoy aligned incentives, flexibility, and adaptability.

Morphological and physiological variation between queens and workers of Protonectarina sylveirae (de Saussure) (Hymenoptera, Vespidae, Epiponini)

Morphological and physiological variation between queens and workers of Protonectarina sylveirae (de Saussure) (Hymenoptera, Vespidae, Epiponini). The Neotropical swarm-founding wasps, Epiponini, range from the absence of morphological differentiation between castes to highly distinct castes. We measured eight body parts of females of two colonies of Protonectarina sylveirae (de Saussure, 1854). ANOVA and Discriminant Analysis evidenced significant differences between castes, as previously observed by other authors for other species of Epiponini. However, some females previously categorized as queens, were actually workers, supported by our statistic analyses. These individuals showed intermediate morphological features between queens and workers, having distinct patterns of hairs and clypeal spots. The castes of P. sylveirae are distinct, however intermediate individuals may be found in colonies promoting social flexibility.

Peptídeos de conformação restrita induzida pela incorporação de unidades (aza)lactâmicas

Conformational constraint is an approach which can be used to restrict the flexibility of peptide molecules and to provide information on the topographical requirements of receptors. The incorporation of conformationally constrained units in a peptide can lead to peptide analogues that present numerous advantages such as the potentialization of the pharmacological activity and the decrease of enzymatic degradation. This review discusses the peptide analogues containing a lactam or azalactam unit in their sequences. Of particular interest has been the replacement of a dipeptide motif in a peptide that simulates a beta-turn.

Sistema de alimentação gás-líquido para medidas de atividade catalítica

This note has as objective to present the advantages of the use of syringe-type pumps for the feeding of liquid reactants, together with mass flow controllers for gases, instead of the saturators, as it is generally accomplished. Among the advantages, the system with syringe pumps presents a greater flexibility in flow control as well as in composition compared with the system that uses saturator. In addition, the flow of the liquid reactants is known with precision in the syringe pump system.

Um paradigma da química medicinal: a flexibilidade dos ligantes e receptores

In general, molecular modeling techniques applied in medicinal chemistry have been static and drug based. However the active site geometry and the intrinsic flexibility of both receptor and ligand are fundamental properties for molecular recognition and drug action. As a consequence, the use of dynamic models to describe the ligand-receptor complex is becoming a more common procedure. In this work we discuss the relevance of considering the receptor structure in medicinal chemistry studies as well as the flexibility of the ligand-receptor complex.

Um aparato para monitorar reações rápidas: um "stopped-flow" artesanal de baixo custo

The modern stopped-flow reaction analyzer has shown high efficiency and flexibility, which provides outstanding sample economy with a dead-time of less than 1 ms. However the cost of the equipment imposes a serious restriction to many Brazilian scientists and teachers. In this work we describe the construction of a low-cost stopped-flow system coupled to a UV-Vis spectrophotometer. The performance of the system was checked by monitoring the kinetics of two reactions: the fading of phenolphthalein in aqueous alkaline solution and the chlorophyll a demetallation in acid medium. The apparatus showed reasonable efficiency with a dead-time of 0.3 to 0.5 s. The very good results obtained in these two illustrative processes show that the system is satisfactory for determining rate constants with mean reaction times ranging from seconds to minutes.

Influência do sulfato de condroitina na formação de filmes isolados de polimetacrilato: avaliação do índice de intumescimento e permeabilidade ao vapor d'água

Natural or modified chondroitin sulfate was incorporated in to polymethacrylate to obtain isolated films. The addition of polysaccharide to synthetic polymers occurred at different rates. Isolated films were micro and macroscopically characterized and swelling index and water vapor transmission were determined. Results indicated changed transparency and flexibility, coupled to their dependence on increase in polysaccharide concentration. A similar occurrence was reported in the permeability to water vapor and swelling degree. Films composed of modified chondroitin sulfate, 90:10 concentration, showed hydration levels, permeability and morphological properties which allow them to be applied as excipients in the development of new drug delivery systems.

Síntese de copolímeros em bloco com propriedades líquido cristalinas

The principal techniques for the synthesis of liquid crystalline block copolymers are reviewed. The syntheses are done by living/controlled free radical chain polymerization. The copolymers display an amorphous continuous phase and a discontinuous liquid crystalline phase (LC). The presence of oxypropylenic segments disturbs the range of mesophase transitions at lower temperatures. This behavior is not observed when styrenic segments are employed and suggests that the liquid crystalline behavior can be modified in block copolymers to show mesophases at higher and lower temperatures according to the flexibility of the chain segment that is present.

Propriedades físicas de filmes biodegradáveis à base de amido de mandioca, álcool polivinílico e montmorilonita

The objective of this work was to manufacture biodegradable films based on cassava starch, polyvinyl alcohol (PVA) and sodium montmorillonite (Na-MMT), using glycerol as a plasticizer. These films were characterized according to their microstructure, optical, mechanical, and barrier properties. The combination of starch-PVA-MMT resulted in films with a more homogeneous surface than starch films. The introduction of PVA into the starch matrix led to the formation of films with lower water vapor permeability (WVP), higher tensile strength and greater elongation. MMT was exfoliated in the films, resulting in greater stability for different relative humidities, lower WVP, higher resistance and lower flexibility.

EFEITO DOS TRATAMENTOS SUPERFICIAIS NAS PROPRIEDADES DO BAGAÇO DA FIBRA DE PIAÇAVA Attalea funifera Martius

The aim of this study was to investigate the effect of surface treatment on the properties of waste piassava fiber with the goal of aggregating additional business value. The fiber surface was subjected to four different treatments. In the present work, it was found that washing the fibers with water partially removed impurities from the surface rendering it rougher. Alkaline treatment removed impurities from the surface, hemicellulose and lignin, improving the flexibility of the fibers. Increasing the concentration of washing agents, times and temperature of treatment promoted intense defibrillation on the fiber surface, reducing its strength.

APLICAÇÃO DE ÓXIDOS DE FERRO NANOESTRUTURADOS COMO ADSORVENTES E FOTOCATALISADORES NA REMOÇÃO DE POLUENTES DE ÁGUAS RESIDUAIS

New techniques for treating wastewater, particularly the removal or degradation of organic pollutants and heavy metals, among other pollutants, have been extensively studied. The use of nanostructured iron oxides as adsorbent and photocatalyst for the removal of these contaminants has proved a promising approach, not only because of their high treatment efficiency, but also for their cost-effectiveness, having the flexibility for in situ and ex situ applications. In this review, we briefly introduced the most used kinds of iron oxide nanoparticles, some synthesis techniques for iron oxide nanostructure formation, their potential benefits in environmental clean-up, and their recent advances and applications in wastewater treatment. These advances range from the direct applications of synthesized nanoparticles as adsorbents for removing toxic contaminants or as catalysts to oxidize and break down noxious contaminants (including bacteria and viruses) in wastewater, to integrating nanoparticles into conventional treatment technologies, such as composite photocatalytic filters (membranes, sand and ceramic) that combine separation technology with photocatalytic activity. Finally, the impact of nanoparticles on the environment and human health is briefly discussed.

Mapping of summer crops in the State of Paraná, Brazil, through the 10-day spot vegetation NDVI composites

The search for low subjectivity area estimates has increased the use of remote sensing for agricultural monitoring and crop yield prediction, leading to more flexibility in data acquisition and lower costs comparing to traditional methods such as census and surveys. Low spatial resolution satellite images with higher frequency in image acquisition have shown to be adequate for cropland mapping and monitoring in large areas. The main goal of this study was to map the Summer crops in the State of Paraná, Brazil, using 10-day composition of NDVI SPOT Vegetation data for 2005/2006, 2006/2007 and 2007/2008 cropping seasons. For this, a supervised digital classification method with Parallelepiped algorithm in multitemporal RGB image composites was used, in order to generate masks of Summer cultures for each 10-day composition. Accuracy assessment was performed using Kappa index, overall accuracy and Willmott's concordance index, resulting in good levels of accuracy. This methodology allowed the accomplishment, with free and low resolution data, of the mapping of Summer cultures at State level.

Influence of stiffness in bolted connections in wooden plane structure of truss type

Trusses are structural systems commonly used in projects, being employed mainly in roof structures, present in most rural buildings. The design of trusses, as well as other structural systems, requires the determination of displacements, strains and stresses. However, the project is developed from an ideal model of calculation, considering free rotation between the elements of a connection. This paper presents a computer program for the analysis of bidimensional wooden trusses with connections formed with two screws per node. The formulation is based on the flexibility method, taking into account the influence of the effect of semi-rigid connections formed by two screws. An example of a structure is presented and analyzed by the program developed here, highlighting the importance of behavior analysis on semi-rigid connections.

On the Efficiency of Alternatives in Process Plans

Process planning is a very important industrial activity, since it determines how a part or a product is manufactured. Process planning decisions include machine selection, tool selection, and cutting conditions determination, and thus it is a complex activity. In the presence of unstable demand, flexibility has become a very important characteristic of today's successful industries, for which Flexible Manufacturing Systems (FMSs) have been proposed as a solution. However, we believe that FMS control software is not flexible enough to adapt to different manufacturing system conditions aiming at increasing the system's efficiency. One means to overcome this limitation is to include pre-planned alternatives in the process plan; then planning decisions are made by the control system in real time to select the most appropriate alternative according to the conditions of the shop floor. Some of the advantages of this approach reported in the literature are the reduction of the number of tool setups, and the selection of a replacement machine for executing an operation. To verify whether the presence of alternatives in process plans actually increases the efficiency of the manufacturing system, an investigation was carried out using simulation and design of experiments techniques for alternative plans on a single machine. The proposed methodology and the results are discussed within this paper.