41 research outputs found
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Reconstitution of the E. Coli Membrane -Barrel Assembly Machine from Purified Components
-barrel membrane proteins perform important functions in the outer membranes of Gram-negative bacteria and in the mitochondria and chloroplasts of eukaryotes. Cellular machines that have been conserved from bacteria to humans assemble these proteins by an unknown mechanism. The components of the -barrel assembly machine (Bam) in E. coli have been identified, but it has been difficult to study their function in vivo because they catalyze an essential process; mutations in proteins involved in the assembly pathway are often lethal or produce pleiotropic phenotypes that do not reveal the specific roles of the individual proteins. This study describes an in vitro reconstitution of the activity of the Bam complex and the use of this assay to determine how the Bam proteins contribute to the assembly of the complex itself. A sensitive assay for -barrel assembly was developed using a substrate protein that has protease activity when it is folded. A peptide bond cleavage thereby reports on the conformational change the Bam complex catalyzes. This assay demonstrates that the Bam proteins dramatically increase the rate of -barrel assembly without any external energy source. The structures of these proteins must inherently facilitate the folding and insertion process. The in vitro reconstitution was then adapted to study the assembly of the central component of the Bam complex, BamA. These studies reveal that the conserved domains of BamA catalyze the steps in the assembly process that are common in all organisms. The accessory components of the Bam complex adapt the mechanism of BamA to improve its efficiency and to allow it to handle a diverse set of substrates. The assembly of the Bam complex thus demonstrates how a cellular machine evolves to achieve generality and high efficiency. A structure of the Bam complex will be required to understand the molecular details of how substrate proteins are bound, folded into -barrel structures, and inserted into the membrane. Initial efforts indicate that it will be possible to obtain such a structure. By combining structural and biochemical information garnered from the in vitro reconstitution, the general principles that guide the assembly of membrane -barrels may be determined.Chemistry and Chemical Biolog
Socio-economic impact of ecological agriculture at the territorial level
This deliverable investigates the socio-economic effects of ecological approaches to farming through implementing two participatory approaches, namely Delphi exercise and Q-method, at the level of a case study area (CSA). The focus is on how people and other productive assets are employed and remunerated by ecological approaches to agriculture, particularly those aspects that can influence employment, and drive the prosperity and vitality of local communities and some rural businesses. It is based on the collaborative research on Task 4.2 ‘Socio-economic impact of ecological agriculture at the territorial level’ of the LIFT project between UNIKENT (United Kingdom-UK) (Task Leader), BOKU (Austria), INRAE (France), VetAgro Sup (France), DEMETER (Greece), MTA KRTK (Hungary), UNIBO (Italy), IRWiR PAN (Poland), IAE-AR (Romania), SLU (Sweden), SRUC (UK). Beginning with the Delphi exercise, this deliverable presents qualitative information extracted from stakeholders in the following four steps. First, the researchers build a presentation of differences between ecological and conventional farming approaches in each CSA. Second, stakeholders elaborate on how they understand ecological farming approaches to exist in each CSA. Third, stakeholders develop a scenario of adoption of ecological approaches to farming depending on two factors: pattern (ecological farms forming clusters or randomly spread within the territory) and rate of adoption 10 years in the future. After establishing this scenario across two rounds, the stakeholders explore the socio-economic effects of their adoption scenario. The Q-methodology then presents a Q-set of statements that the Delphi has developed and, through factor analysis,studies the key stakeholder perspectives of the socio-economic effects of the perceived adoption of ecological practices in 10 years in the future. Four key results can be derived from the Delphi exercise and the Q-methodology. First, a higher adoption of ecological farming approaches, especially so at a 50% adoption rate, is mostly thought by stakeholders in the Delphi Exercise to lead to an increase in skill level and quality of life in on-farm employment. This is as a result of an increased diversity of farming enterprises on farms using ecological farming approaches, the interest generated from this, the knowledge of natural processes and biology required, engagement with nature and change in machinery that is coming into the industry. Strongly related to this need for skills is a predicted increase in the number of advisers and civil servants to deal with more complicated farms and incentives as well as monitoring of ecological effects on farm. An increase in required skill level is repeated across all Q-studies. Second, especially where farms are clustered together, Delphi Exercise respondents predict an increase in the trade of inputs such as manure and compost replacing synthetic fertiliser, as well as more sharing of capital and labour. Q-methodology highlights that these clusters may support a stronger social movement, more consumers buying local food and increase collaboration between farmers. Supply chains are expected to become shorter as farmers sell more directly and there are fewer intermediaries upstream of the farming sector. As farmers collaborate more with each other on environmental objectives, trading inputs and sharing best practices, farmer relationships should improve in rural communities. Third, Delphi exercise finds that contracting, machinery purchasers, and machinery traders and dealers could increase, decrease or display no change – the anticipated effects are mixed. Stakeholders are in no doubt that machinery use will change and therefore new skills will need to be learnt, but the wider effect on machinery purchase is uncertain. However, stakeholders conclude that a greater specialisation in machinery will occur leading to changes in farm management as well as the suppliers of this machinery. Q-methodology highlights that ecological practices will not mean the end of machinery and a lot more labour – often machinery will be useful in weeding and reducing physical labour as technology has significantly improved and skills are improving too in order to use these technologies. Fourth, Delphi respondents argued that although rural populations might be little affected by ecological farming, a shift in people moving from urban to rural settlements, and thereby a higher rural population density, seeking a more attractive rural environment, might contribute to higher local consumer demand. The Q-methodology highlights that where there is high adoption, rural areas are expected to become more attractive, as landscapes will have a much greater variety of crops instead of fields of monocrops. This variety of crops may include agroforestry (farmers interested in ecological approaches to farming may also be interested in agroforestry as a way of boosting their yields and protecting crops and livestock from the elements) as well as intercropping
Migrations résidentielles de l’urbain vers le rural en France : différenciation sociale des profils et ségrégation spatiale.
D’après l’analyse du dernier recensement de population (1990-99), le rural gagne de la population, grâce à des apports migratoires, alors que les villes en perdent (Bessy-Piettri et al., 2000). Doit-on alors abonder les interprétations qui en font le signe d’une attractivité des campagnes à la faveur du cadre de vie qu’elles procurent ou poursuivre les analyses qui privilégient les effets de ségrégation résidentielle repoussant toujours plus loin ceux qui n’ont pas les ..
Mangifera indica (L.) et Sorghum bicolor (L.) (approche et utilisation traditionnelle dans une préparation anti-anémique au sein d'un centre de soins au Bénin)
Au Bénin et de manière générale dans toute l'Afrique sub-saharienne, la disponibilité et le prix plus abordable rendent les plantes médicinales plus attrayantes en tant qu'agents thérapeutiques par rapport aux médicaments de la médecine conventionnelle. Mon expérience de terrain s'est effectuée dans un centre de soins béninois où les patients sont pris en charge par des remèdes traditionnels dans la grande majorité des cas ; ces derniers sont préparés sur place et sont issus d'un savoir ancestral. En l'occurrence, un de ces remèdes nommé FORTE, préparé à base de deux drogues végétales issues du manguier (Mangifera indica) et du sorgho (Sorghum bicolor), est prescrit pour ses propriétés traditionnelles anti-anémiques. Ma démarche ethnopharmacologique concernant cette préparation a consisté entre autre par le suivi du taux d'hémoglobine des patients traités, mais aussi par l'analyse des résultats d'un questionnaire portant sur son usage et qui a été proposé aux patients se présentant à la pharmacie du centre. Enfin, elle s'est poursuivie par l'étude de sa composition phytochimique révélant entre autre la présence de composés anti-oxydants utiles dans le maintien de l'intégrité membranaire des cellules et notamment celle des globules rouges.NANTES-BU Médecine pharmacie (441092101) / SudocSudocFranceF
Pays et intercommunalité, quelles conséquences de la réforme des collectivités territoriales?
Le rôle des territoires de projets infra-régionaux sur l’agriculture et l’alimentation.
L’article traite de la place de l’agriculture dans les processus de territorialisation des politiques publiques. Le questionnement est centré sur la pertinence de l’échelon infra-régional pour intervenir sur l’agriculture et la sphère agroalimentaire et sur sa capacité à articuler ses interventions avec celles des autres niveaux d’action publique. La démonstration s’appuie sur l’exploitation de données statistiques sur les caractéristiques socio-économiques du territoire et de l’agriculture et sur l’analyse des programmes de développement des Pays « Voynet » en Bourgogne, complétée par des analyses qualitatives sur quelques Pays. L’article montre que, malgré un contexte de régulation très sectorielle de l’agriculture, les Pays interviennent de façon croissante sur l’agriculture et tout particulièrement sur l’organisation de circuits de commercialisation de proximité tant en contexte urbain que rural.The article discusses the role of agriculture in the process of regionalization of public policy. The study focuses on the relevance of the sub-regional level to develop agriculture and its ability to articulate local actions with other levels of public action. The demonstration is based on a statistical data analysis on the socio-economic characteristics of the land and agriculture and on the analysis of development programmes of the "pays Voynet" in Burgundy, supplemented by qualitative analysis from case studies. The article shows that, despite a very sectoral regulation of agriculture, the ‘pays’ are increasingly involved in agriculture, especially for the organization of local food markets both in urban and rural contexts
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Pays et intercommunalité, quelles conséquences de la réforme des collectivités territoriales?
Une analyse de la géographie des services résidentiels et touristiques à l'échelle des bassins de vie français
The objective of this paper is to contribute to the characterization of "residential" activities that correspond to services to the population, be it permanent or temporary, in a given locality. The spatial distribution of employment in these population-based activities is analyzed at the geographic scale of functional economic areas. The estimation of tourism-related employment uses the minimum requirements technique to assess the specific impact of tourism attractiveness on the population-based services. To explain the geography of population-based employment, explanatory factors relate to local market potential and the ability of territories to attract or retain consumers. Though, generally speaking, the distribution of population-based employment follows the urban hierarchy, one should also take account of sectoral characteristics that set non-market services somewhat apart, as well as geographic specificities in periurban areas and tourism resorts.population-based economy, location factors, tourism employment, minimum requirements approach
Structure économique des territoires : une analyse des disparités micro-régionales à l'échelle des pays en France
An understanding of economic and social disparities at the micro-regional level primarily involves relations between urban and rural areas. We examine the ?pays? as established by legislation on territorial planning and development, drawing up an inventory of these areas which were set up on a political basis but which are large enough for development issues to be envisaged. This article draws on input from regional economics in an attempt to account for the diversity of local arrangements regarding ?pays? on the basis of spatial structuring criteria which combine the rural/urban distinction and the occurrence of towns. Cluster thus established is submitted to a multinomial logit model to analyse the discriminant character of economic variables relating to the sectoral structure, the labour market, population services and social structures. Each class of ?pays? is then characterised in terms of its development potential.regional economics, micro-regional growth, territory, “Pays” policy
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Inhibition of the βbarrel assembly machine by a peptide that binds BamD
The protein complex that assembles integral membrane β-barrel proteins in the outer membranes of Gram-negative bacteria is an attractive target in the development of new antibiotics. This complex, the β-barrel assembly machine (Bam), contains two essential proteins, BamA and BamD. We have identified a peptide that inhibits the assembly of β-barrel proteins in vitro by characterizing the interaction of BamD with an unfolded substrate protein. This peptide is a fragment of the substrate protein and contains a conserved amino acid sequence. We have demonstrated that mutations of this sequence in the full-length substrate protein impair the protein’s assembly,implying that BamD’s interaction with this sequence is an important part of the assembly mechanism. Finally, we have found that in vivo expression of a peptide containing this sequence causes growth defects and sensitizes E. coli to antibiotics to which they are normally resistant. Therefore, inhibiting the binding of substrates to BamD is a viable strategy for developing new antibiotics directed against Gram-negative bacteria.Chemistry and Chemical Biolog