Redox properties and electron paramagnetic resonance spectroscopy of the transition state complex of Azotobacter vinelandii nitrogenase

AbstractNitrogenase is a two-component metalloenzyme that catalyzes a MgATP hydrolysis driven reduction of substrates. Aluminum fluoride plus MgADP inhibits nitrogenase by stabilizing an intermediate of the on-enzyme MgATP hydrolysis reaction. We report here the redox properties and electron paramagnetic resonance (EPR) signals of the aluminum fluoride-MgADP stabilized nitrogenase complex of Azotobacter vinelandii. Complex formation lowers the midpoint potential of the [4Fe-4S] cluster in the Fe protein. Also, the two-electron reaction of the unique [8Fe-7S] cluster in the MoFe protein is split in two one-electron reactions both with lower midpoint potentials. Furthermore, a change in spin-state of the two-electron oxidized [8Fe-7S] cluster is observed. The implications of these findings for the mechanism of MgATP hydrolysis driven electron transport within the nitrogenase protein complex are discussed

Do synovial biopsies help to support evidence for involvement of innate immunity in the immunopathology of Behçet's disease?

Behçet's disease is a complex vasculitis of unknown etiology. Abundant neutrophils suggest the involvement of innate immunity. Cytokines are skewed to the T-helper-1 pattern. Few sterile organs are easily accessible for analysis in Behçet's disease. Cañete and coworkers identify inflamed joints as a feasible model and suggest the involvement of innate immunity in Behçet's disease

Innovation through (international) food supply chain development. A research agenda

This paper presents a research agenda on innovation through (international) food supply chains and networks in developing countries. It derives major topics from a multi-perspective view on international food chains (economic, technology, social/legal and environment) and from different theoretical streams dealing with chains and networks (Supply Chain Management, Industrial Organization theory and Network Theory). Three agri-supply chain projects in developing countries (Thailand, South-Africa, Ghana) are analyzed to identify focus areas in supply chain development projects and important gaps. These projects were collaborative actions between companies and research institutes to initiate international supply chain development

The Selective Autophagy Receptor p62 Forms a Flexible Filamentous Helical Scaffold

Published version also available at http://dx.doi.org/10.1016/j.celrep.2015.03.062The scaffold protein p62/SQSTM1 is involved in protein turnover and signaling and is commonly found in dense protein bodies in eukaryotic cells. In autophagy, p62 acts as a selective autophagy receptor that recognizes and shuttles ubiquitinated proteins to the autophagosome for degradation. The structural organization of p62 in cellular bodies and the interplay of these assemblies with ubiquitin and the autophagic marker LC3 remain to be elucidated. Here, we present a cryo-EM structural analysis of p62. Together with structures of assemblies from the PB1 domain, we show that p62 is organized in flexible polymers with the PB1 domain constituting a helical scaffold. Filamentous p62 is capable of binding LC3 and addition of long ubiquitin chains induces disassembly and shortening of filaments. These studies explain how p62 assemblies provide a large molecular scaffold for the nascent autophagosome and reveal how they can bind ubiquitinated cargo

Benchmarking tomographic acquisition schemes for high-resolution structural biology

Cryo electron tomography with subsequent subtomogram averaging is a powerful technique to structurally analyze macromolecular complexes in their native context. Although close to atomic resolution in principle can be obtained, it is not clear how individual experimental parameters contribute to the attainable resolution. Here, we have used immature HIV-1 lattice as a benchmarking sample to optimize the attainable resolution for subtomogram averaging. We systematically tested various experimental parameters such as the order of projections, different angular increments and the use of the Volta phase plate. We find that although any of the prominently used acquisition schemes is sufficient to obtain subnanometer resolution, dose-symmetric acquisition provides considerably better outcome. We discuss our findings in order to provide guidance for data acquisition. Our data is publicly available and might be used to further develop processing routines

On the gauge and BRST invariance of the chiral QED with Faddeevian anomaly

Chiral Schwinger model with the Faddeevian anomaly is considered. It is found that imposing a chiral constraint this model can be expressed in terms of chiral boson. The model when expressed in terms of chiral boson remains anomalous and the Gauss law of which gives anomalous Poisson brackets between itself. In spite of that a systematic BRST quantization is possible. The Wess-Zumino term corresponding to this theory appears automatically during the process of quantization. A gauge invariant reformulation of this model is also constructed. Unlike the former one gauge invariance is done here without any extension of phase space. This gauge invariant version maps onto the vector Schwinger model.The gauge invariant version of the chiral Schwinger model for $a=2$ has a massive field with identical mass however gauge invariant version obtained here does not map on to that.Comment: 11 pages latex, no figures, A little change in Title and abstrac

Genome-wide association study in an admixed case series reveals IL12A as a new candidate in Behçet Disease

Introduction: The etiology of Behçet's disease (BD) is unknown, but widely considered an excessive T-cell mediated inflammatory response in a genetically susceptible host. Recent genomewide association studies (GWAS) have shown limited number of novel loci-associations. The rarity and unequal distribution of the disease prevalence amongst different ethnic backgrounds have hampered the use of GWAS in cohorts of mixed ethnicity and sufficient sample size. However, novel statistical approaches have now enabled GWAS in admixed cohorts. Methods: We ran a GWAS on 336 BD cases and 5,843 controls. The cases consisted of Western Europeans, Middle Eastern and Turkish individuals. Participants from the Generation R study, a multiethnic birth cohort in Rotterdam, The Netherlands were used as controls. All samples were genotyped and data was combined. Linear regression models were corrected for population stratification using Genomic Principal Components and Linear Mixed Modelling. Meta-analysis was performed on selected results previously published. Results: We identified SNPs associated at genome-wide significant level mapping to the 6p21.33 (HLA) region. In addition to this known signal two potential novel associations on chromosomes 6 and 18 were identified, yet with low minor allele frequencies. Extended metaanalysis reveal a GWS association with the IL12A variant rs17810546 on chromosome 3. Discussion: We demonstrate that new statistical techniques enable GWAS analyses in a limited sized cohort of mixed ethnicity. After implementation, we confirmed the central role of the HLA region in the disease and identified new regions of interest. Moreover, we validated the association of a variant in the IL2A gene by meta-analysis with previous work. These findings enhance our

Interatomic potentials for atomistic simulations of the Ti-Al system

Semi-empirical interatomic potentials have been developed for Al, alpha-Ti, and gamma-TiAl within the embedded atomic method (EAM) by fitting to a large database of experimental as well as ab-initio data. The ab-initio calculations were performed by the linear augmented plane wave (LAPW) method within the density functional theory to obtain the equations of state for a number of crystal structures of the Ti-Al system. Some of the calculated LAPW energies were used for fitting the potentials while others for examining their quality. The potentials correctly predict the equilibrium crystal structures of the phases and accurately reproduce their basic lattice properties. The potentials are applied to calculate the energies of point defects, surfaces, planar faults in the equilibrium structures. Unlike earlier EAM potentials for the Ti-Al system, the proposed potentials provide reasonable description of the lattice thermal expansion, demonstrating their usefulness in the molecular dynamics or Monte Carlo studies at high temperatures. The energy along the tetragonal deformation path (Bain transformation) in gamma-TiAl calculated with the EAM potential is in a fairly good agreement with LAPW calculations. Equilibrium point defect concentrations in gamma-TiAl are studied using the EAM potential. It is found that antisite defects strongly dominate over vacancies at all compositions around stoichiometry, indicating that gamm-TiAl is an antisite disorder compound in agreement with experimental data.Comment: 46 pages, 6 figures (Physical Review B, in press

Kjemisk behandling mot Gyrodactylus salaris i Steinkjervassdragene 2006

Årsliste 2007Kjemisk behandling mot Gyrodactylus salaris i Steinkjervassdraget er gjennomført på oppdrag fra Direktoratet for naturforvalting (DN). Tiltakshaver har vært Fylkesmannen (FM) i Sogn og Fjordane. Behandlingen av Steinkjervassdraget høsten 2006 er en del av en totalbehandling som har som hovedmål å utrydde lakseparasitten G. salaris i regionen. Hensikten med behandlingen i august 2006 var å redusere smitten av G. salaris internt i Steinkjervassdragene og eksternt til nærliggende vassdrag i regionen. Dette ble gjort ved å tilsette surt aluminiumsulfat (AlS) i elvevannet og CFT-L (rotenon) i dammer og sig. Behandlingen foregikk i tidsrommet 21.august-2.september 2006. AlS ble dosert ut i hovedelvene og i de største sidevassdragene. I andre små vannkilder i periferien, som for eksempel små sig og mindre avsnørte dammer ble det brukt CFT-Legumin (rotenon). Under behandlingen ble det dosert ut totalt 2 tonn med aluminium og 11 liter CFT-Legumin (0,3 kg rotenon). Lakseunger infisert med G. salaris ble plassert i kar langs elva og eksponert for behandlet elvevann. Ved behandlingens slutt ble alle lakseungene i karene sjekket for G. salaris. Ingen dødelighet ble registrert og det ble heller ikke funnet G. salaris på noen av fiskene i karene.Direktoratet for naturforvaltning