Structural and mutational characterization of the catalytic A-module of the mannuronan C-5-epimerase AlgE4 from Azotobacter vinelandii

Alginate is a family of linear copolymers of (1→4)-linked β-d-mannuronic acid and its C-5 epimer α-l-guluronic acid. The polymer is first produced as polymannuronic acid and the guluronic acid residues are then introduced at the polymer level by mannuronan C-5-epimerases. The structure of the catalytic A-module of the Azotobacter vinelandii mannuronan C-5-epimerase AlgE4 has been determined by x-ray crystallography at 2.1-Å resolution. AlgE4A folds into a right-handed parallel β-helix structure originally found in pectate lyase C and subsequently in several polysaccharide lyases and hydrolases. The β-helix is composed of four parallel β-sheets, comprising 12 complete turns, and has an amphipathic α-helix near the N terminus. The catalytic site is positioned in a positively charged cleft formed by loops extending from the surface encompassing Asp(152), an amino acid previously shown to be important for the reaction. Site-directed mutagenesis further implicates Tyr(149), His(154), and Asp(178) as being essential for activity. Tyr(149) probably acts as the proton acceptor, whereas His(154) is the proton donor in the epimerization reaction

Abnormal thymic stromal lymphopoietin expression in the duodenal mucosa of patients with coeliac disease

OBJECTIVE: The short isoform of thymic stromal lymphopoietin (TSLP), a cytokine constitutively expressed by epithelial cells, is crucial in preserving immune tolerance in the gut. TSLP deficiency has been implicated in sustaining intestinal damage in Crohn's disease. We explored mucosal TSLP expression and function in refractory and uncomplicated coeliac disease (CD), a T-cell-mediated enteropathy induced by gluten in genetically susceptible individuals. DESIGN: TSLP isoforms-long and short-and receptors-TSLPR and interleukin (IL)-7Rα-were assessed by immunofluorescence, immunoblotting and qRT-PCR in the duodenum of untreated, treated, potential and refractory patients with CD. The ability of the serine protease furin or CD biopsy supernatants to cleave TSLP was evaluated by immunoblotting. The production of interferon (IFN)-γ and IL-8 by untreated CD biopsies cultured ex vivo with TSLP isoforms was also assessed. RESULTS: Mucosal TSLP, but not TSLPR and IL-7Rα, was reduced in untreated CD and refractory CD in comparison to treated CD, potential CD and controls. Transcripts of both TSLP isoforms were decreased in active CD mucosa. Furin, which was overexpressed in active CD biopsies, was able to cleave TSLP in vitro. Accordingly, refractory and untreated CD supernatants showed higher TSLP-degrading capacity in comparison to treated CD and control supernatants. In our ex vivo model, both TSLP isoforms significantly downregulated IFN-γ and IL-8 production by untreated CD biopsies. CONCLUSIONS: Reduced mucosal TSLP expression may contribute to intestinal damage in refractory and untreated CD. Further studies are needed to verify whether restoring TSLP might be therapeutically useful especially in refractory patients with CD

Genome-Wide Transcript Profiling of Endosperm without Paternal Contribution Identifies Parent-of-Origin–Dependent Regulation of AGAMOUS-LIKE36

Seed development in angiosperms is dependent on the interplay among different transcriptional programs operating in the embryo, the endosperm, and the maternally-derived seed coat. In angiosperms, the embryo and the endosperm are products of double fertilization during which the two pollen sperm cells fuse with the egg cell and the central cell of the female gametophyte. In Arabidopsis, analyses of mutants in the cell-cycle regulator CYCLIN DEPENDENT KINASE A;1 (CKDA;1) have revealed the importance of a paternal genome for the effective development of the endosperm and ultimately the seed. Here we have exploited cdka;1 fertilization as a novel tool for the identification of seed regulators and factors involved in parent-of-origin–specific regulation during seed development. We have generated genome-wide transcription profiles of cdka;1 fertilized seeds and identified approximately 600 genes that are downregulated in the absence of a paternal genome. Among those, AGAMOUS-LIKE (AGL) genes encoding Type-I MADS-box transcription factors were significantly overrepresented. Here, AGL36 was chosen for an in-depth study and shown to be imprinted. We demonstrate that AGL36 parent-of-origin–dependent expression is controlled by the activity of METHYLTRANSFERASE1 (MET1) maintenance DNA methyltransferase and DEMETER (DME) DNA glycosylase. Interestingly, our data also show that the active maternal allele of AGL36 is regulated throughout endosperm development by components of the FIS Polycomb Repressive Complex 2 (PRC2), revealing a new type of dual epigenetic regulation in seeds

A Semantic Middleware Supported Receding Horizon Optimal Power Flow in Energy Grids

Energy management in electric grids with multiple energy sources, generators, storage devices, and interacting loads along with their complex behaviors requires grid wide control. Communication infrastructure that aggregates information from heterogeneous devices in the electric grid making the applications completely independent of physical connectivity is essential for building in the context of control applications. This investigation presents a semantic middleware that is used to implement a receding-horizon-based optimal power flow (OPF) in smart grids. The presence of renewable energy sources, storage systems, and loads dispersed all along the grid necessitates the use of grid wide control and a communication infrastructure to support it. To this extent, the proposed middleware will serve as the basis for representing various components of the power grid. It is enriched with intelligence by semantic annotation and ontologies that provide situation awareness and context discovery. The middleware deployment is demonstrated by implementing the receding horizon OPF in a network in Steinkjer, Norway. Our results demonstrate the advantages of both the middleware and the algorithm. Furthermore, the results prove the added flexibility obtained in the grid due to the addition of renewable energy and storage systems. The significant advantage of the proposed approach is that the real-time monitoring infrastructure is used for improving the flexibility, reliability, and efficiency of the grid

Optimal Power Flow model with energy storage, an extension towards large integration of renewable energy sources

The integration of renewable energy sources (RES) into modern electrical grids contributes to satisfying the continuously increasing energy demand. This can be done in a sustainable way since renewable sources are both inexhaustible and non-polluting. Different renewable energy devices, such as wind power, hydro power, and photovoltaic generators are available nowadays. The main issue with the integration of such devices is their irregular generation capacity (in particular for wind and solar energy). Therefore energy storage units are used to mitigate the fluctuations during generation and supply. In this paper we formulate a model for the Alternate Current Optimal Power Flow (ACOPF) problem consisting of simple dynamics for energy storage systems cast as a finite-horizon optimal control problem. The effect of energy storage is examined by solving a Norwegian demo network. The simulation results illustrate that the addition of energy storage, along with demand based cost functions, significantly reduces the generation costs and flattens the generation profiles

Demonstrating Active Distribution Grids and Active Demand 

Active distribution grids and active customers require a rethinking of ICT tools and architectures in order to connect systems, platforms and actors previously unable to exchange information across domains of the energy business. This paper presents results from an R&D project focusing on developing a reference architecture for an open smart grid middleware, able to cope with the wide range of services necessary to integrate both DSOs, retailers and consumers as well as new actors (such as aggregators and prosumers) to a common framework. Such a framework is necessary to develop, scale and design future energy-related services to customers and other relevant stakeholders in the energy system operation

Identification of pathways directly regulated by SHORT VEGETATIVE PHASE during vegetative and reproductive development in Arabidopsis

Background MADS-domain transcription factors play important roles during plant development. The Arabidopsis MADS-box gene SHORT VEGETATIVE PHASE (SVP) is a key regulator of two developmental phases. It functions as a repressor of the floral transition during the vegetative phase and later it contributes to the specification of floral meristems. How these distinct activities are conferred by a single transcription factor is unclear, but interactions with other MADS domain proteins which specify binding to different genomic regions is likely one mechanism. Results To compare the genome-wide DNA binding profile of SVP during vegetative and reproductive development we performed ChIP-seq analyses. These ChIP-seq data were combined with tiling array expression analysis, induction experiments and qRT-PCR to identify biologically relevant binding sites. In addition, we compared genome-wide target genes of SVP with those published for the MADS domain transcription factors FLC and AP1, which interact with SVP during the vegetative and reproductive phases, respectively. Conclusions Our analyses resulted in the identification of pathways that are regulated by SVP including those controlling meristem development during vegetative growth and flower development whereas floral transition pathways and hormonal signaling were regulated predominantly during the vegetative phase. Thus, SVP regulates many developmental pathways, some of which are common to both of its developmental roles whereas others are specific to only one of them

Application of Structural Health Monitoring over a Critical Helicopter Fuselage Component

The helicopter design is a challenging experience for fatigue concern as it is subjected to a very wide range of low- and high-frequency load cycles per flight, very much more than a fixed wing aircraft. Moreover, thinking of the various and harsh environments where the helicopter could operate, also corrosion and low velocity impacts could generate further crack nucleation and propagation into the fuselage. Health and Usage Monitoring Systems (HUMS) has received considerable attention from the helicopter community in recent years with the declared aim to increase flight safety and mission reliability, extend duration of life-limited components and of course reduce inspection and maintenance activities. In particular, Structural Health Monitoring (SHM) seems capable to help in reducing the maintenance and operational costs, which is about 25 per cent of the direct operating cost of the helicopter, thus playing an important role especially in the case of the ageing helicopters. In fact, the damage tolerant design approach makes the fatigue resistance evaluation not only a safety issue but also a maintenance related concern. In effect, thanks to the continuous evaluation of the current structural health of the helicopter through a SHM system, it could be possible to set a Condition Based Maintenance, which means substituting a component according to its current structural condition instead of relying just on the design assumptions. The approach could bring to a maximization of both the machine availability and reliability, thus conjugating safety with economy. Strictly connected to a damage tolerant design, a sensor network is thus needed in order to monitor the structural health of the machine and the recent improvements in non-destructive techniques for crack detection are making the concept more affordable from both the technological and the economical points of view. The aim of the present work is to explain a novel method to apply the SHM concepts on a critical zone of a helicopter fuselage, passing through the creation of a complete FE Model of the fuselage, either in healthy and damaged situations, and considering the different stress distributions caused by a progressive crack in the most critical areas. This would represent the key step for the extraction of information from the sensor data, thus allowing to distinguish between the undamaged and damaged structures. The helicopter tail structure is presented herein as a good candidate for the application and testing of the SHM system. The main reason is the criticality of the region, where the torque generated by tail rotor to balance the rotation induced by the main rotor is undergone. In particular, the attention will be focused on some simplified reinforced panels, well suited to indicate the general behaviour of the entire structure and particularly adapt for the safe and early application on board of the machine