Effect of Eucalyptus globulus leaves extracts on in vitro rumen fermentation, methanogenesis, degradability and protozoa population

The aim of the research was to evaluate the effect of three Eucalyptus globulus extracts rich in phenolic compounds, especially flavonoids, on rumen fermentation, methane (CH4) production, organic matter degradability and protozoa population using an in vitro gas production technique. Four concentrations (0, 50, 75 and 100 mg) of three Eucalyptus extracts (ethyl acetate, n-butanol and aqueous) were added to a diet of ruminants (forage: concentrate ratio 60:40) and incubated at 39°C under anaerobiosis with buffered rumen fluid. After 24 h, the fermentation fluid was analysed for ammonia-N and volatile fatty acids (VFA). Organic matter degradability (OMD) and protozoa were also determined; in vitro gas production was also recorded and CH4 concentration was measured. Compared to the control, CH4 production was significantly lower for ethyl acetate extract (P<0.05), but higher for n-butanol and aqueous extracts. Production of ammonia- N was lower in all Eucalyptus extracts (P<0.05). Propionate production (P<0.05) increased for ethyl acetate and n-butanol extracts, whereas no effect was registered for VFA, for all Eucalyptus extracts. Ethyl acetate extract decreased in vitro OMD (P<0.05), whereas n-butanol and aqueous extracts were comparable to the control. Protozoa population decreased (P<0.05) for all extracts in comparison with the control. Eucalyptus ethyl acetate extract might be promising to be used as a potent anti-methanogenic additive. Moreover, the assessment of the right dosage seems to be important to decrease methane production, without reducing feed nutritional value

Production et caractérisation de la prohormone convertase 13

Biopeptides are synthesised as large pro-protein precursors that have to undergo proteolytic cleavage at positively charged amino acids (Lys and Arg) in order to become active. This cleavage is mediated by a family of subtilin/kexin related calcium dependent serine endoproteinases named prohormone convertases. The present thesis focuses on the endocrine member of the family named PC1/3. PC1/3 is expressed in the regulated secretory pathway of endocrine and neuroendocrine cells, where it was shown to activate various peptide hormones such as proopiomelanocortin (POMC), pro-insulin and pro-glucagon. PC1/3 is synthesized as a large precursor containing a signal peptide, a propeptide, a catalytic domain, a P domain and a C-terminal domain. The activation of the enzyme requires the sequential removal of the signal peptide, the propeptide and ultimately the C-terminal domain.The structural characterisation of the enzyme is compromised by the difficulty in producing a sufficient amount of recombinant PC1/3. In this thesis it is clearly demonstrated that the production of PC1/3 using Baculovirus technology can be greatly improved by modifying the expression vector in insect cells (Spodoptera frugiperda). In addition, the intracoelemic injection of insect larvae (Tricoplusia ni) with the Baculovirus encoding the recombinant PC1/3 is shown to be a very efficient method for the production of a large amount of prohormone convertases.It was previously demonstrated that the propeptide is essential for the folding of the enzyme and act as a tight binding inhibitor of the enzyme until the latter reaches the appropriate compartment for substrate cleavage. To assess the role of certain residues within the propeptide in the inhibition of the cognate enzyme, a mutational analysis by alanine scan was conducted. The results demonstrate that the substitution of a single amino acid can affect markedly the inhibition behavior, potency and selectivity of the propeptide towards the enzyme. Moreover, this mutational analysis allowed the first experimental mapping of the sequence involved in propeptide degradation once its function is achieved.However, PC1/3 also possesses a C-terminal domain which must also be cleaved to allow the full activation of the enzyme. Previous studies showed that this domain is implicated in the sorting of the enzyme to secretory granules. In addition, over expression experiments showed that the C-terminal domain can inhibit the cleavage of certain substrates by PC1/3. The results, presented here, suggest that the CT-peptide acts as a non-essential activator of PC1/3, in vitro, which adds a supplementary level of complexity to the activation process of the enzyme.Finally, based upon our results, it can be proposed that PC1/3 is a very complex enzyme capable of controlling its enzymatic activity through the coordinate action of its various domains. This exceptional mode of self-regulation is unique among all protease families

Optimal reactive power planning technique using multi-agent system

info:eu-repo/semantics/publishe

Utilization of a new biotinylation reagent in the development of a nondiscriminatory investigative approach for the study of cell surface proteins

International audienc

Optimal reactive power planning technique using multi-agent system

Lack of reactive power support may cause undesirable voltage decay leading to total system instability. Thus, appropriate reactive power support scheme should be arranged in order to maintain system stability. This paper presents enhancement of voltage stability system through Optimal reactive power planning technique using a multi-agent system, the proposed method consists of several Bus agents (BAGs) and compensator agents (CAGs). A BAG corresponds to the bus in the substation, while a CAG supervise and control the compensator. From the simulation results, it can be seen the proposed multi-agent system could reach the right solution by making use of only local information. This means that the proposed multi-agent system is a promising approach to more large-scale power system networks.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Single Amino Acid Substitution in the PC1/3 Propeptide Can Induce Significant Modifications of Its Inhibitory Profile toward Its Cognate Enzyme

International audienc

Structural basis and dynamics of Chikungunya alphavirus RNA capping by nsP1 capping pores

Alphaviruses are emerging positive-stranded RNA viruses which replicate and transcribe their genomes in membranous organelles formed in the cell cytoplasm. The nonstructural protein 1 (nsP1) is responsible for viral RNA capping and gates the replication organelles by assembling into monotopic membrane-associated dodecameric pores. The capping pathway is unique to Alphaviruses; beginning with the N 7 methylation of a guanosine triphosphate (GTP) molecule, followed by the covalent linkage of an m 7 GMP group to a conserved histidine in nsP1 and the transfer of this cap structure to a diphosphate RNA. Here, we provide structural snapshots of different stages of the reaction pathway showing how nsP1 pores recognize the substrates of the methyl-transfer reaction, GTP and S-adenosyl methionine (SAM), how the enzyme reaches a metastable postmethylation state with SAH and m 7 GTP in the active site, and the subsequent covalent transfer of m 7 GMP to nsP1 triggered by the presence of RNA and postdecapping reaction conformational changes inducing the opening of the pore. In addition, we biochemically characterize the capping reaction, demonstrating specificity for the RNA substrate and the reversibility of the cap transfer resulting in decapping activity and the release of reaction intermediates. Our data identify the molecular determinants allowing each pathway transition, providing an explanation for the need for the SAM methyl donor all along the pathway and clues about the conformational rearrangements associated to the enzymatic activity of nsP1. Together, our results set ground for the structural and functional understanding of alphavirus RNA-capping and the design of antivirals