1,382 research outputs found
Bep Pierik
No full textRetrat de Bep Pierik caracteritzada com a Galatea per a l'obra Acis and Galatea; imatge emprada per el programa de la seva actuació amb la Camerata d'Amsterdam al XXIIè Festival Internacional de Música de Barcelon
Studies on the iron - sulfur clusters of hydrogenase, sulfite reductase, nitrogenase and the prismane protein
No full textIron-sulfur clusters are present in a large number of proteins. Sofar structures of four types of protein-bound iron-sulfur clusters have been determined by X-ray diffraction: rubredoxin-like, [2Fe-2S], [3Fe-4S] and [4Fe-4S] centers. The presence of any of these clusters in a protein can be predicted by comparison of spectroscopic properties. However a number of multiple-electron transferring enzymes, like the Fe-only hydrogenase, sulfite reductase and nitrogenase MoFe protein have enigmatic iron-sulfur clusters with spectroscopic properties unlike those of the known structures. These enzymes share a high iron and acidlabile sulfur content and the presence of superspin systems with S≥5/2. In this thesis biochemical and spectroscopic studies are presented on the above-mentioned iron-sulfur proteins and two unusual newly discovered iron-sulfur proteins, the 'prismane' protein and nigerythrin.Chapter 2 summarizes new findings on the Fe-only hydrogenase and the redox properties of its cubanes and hydrogen activating iron-sulfur H-cluster. The hydrogenase, aerobically isolated from the sulfate-reducing bacterium Desulfovibrio vulgaris (Hildenborough) was shown to be composed of a mixture of high and low activity charge conformers, which can be isolated and discriminated by chromatographic and electrophoretic techniques. The redox properties of the rhombic S=1/2 EPR signals associated with the H-cluster of hydrogenase preactivated with dithionite or hydrogen were considerably more simple than those reported by Patil and coworkers for the (oxygen-insenstive) resting enzyme. Instead of sequential bell-shaped curves for the rhombic g=2.07 (g=1.96 and g=1.89) and g=2.11 (g=2.05 and g=2.00) EPR signals in reductive dye-mediated titrations, a simple behaviour with two redox states was observed both in reductive and oxidative titrations. The interconversion between the diamagnetic reduced and the oxidized redox state of the H-cluster exhibiting the g=2.11 S=1/2 EPR signal occurred at -307 mV. The bell-shaped nature and the occurrence of the g=2.07 rhombic EPR signal thus was due to the activation process of the H-cluster. By equilibration with H 2 /H +of activated hydrogenase a midpoint potential of -330 mV was determined for the cubanes. A similar midpoint potential was observed in a dyemediated titration of a recombinant hydrogenase lacking the H-cluster. In these experiments no evidence for redox interaction between the two cubanes was seen.In the course of extensive purification procedures of the Fe-hydrogenase it was recognized that an iron-sulfur protein with novel EPR spectroscopic properties occasionally contaminated hydrogenase preparations (Chapter 3). The as isolated form had a substoichiometric S=1/2 EPR signal with g=1.97, g=1.95 and g=1.90. Chemical analysis showed that, although such g-values are typical for Mo 5+= (or W 5+) no metals other than iron were present. The 'molybdenum'-like EPR spectrum disappeared both on reduction and oxidation. In the dithionite reduced form an almost stoichiometric S=1/2 EPR signal was observed. The g-values (g=2.00, 1.82 and 1.32) were reminiscent of those of prismane model compounds in the [6Fe-6S] 3+redox state. Therefore the protein was proposed to be a prismane-containing protein, in agreement with the chemical analysis indicating ≈6 Fe/protein. The occurrence of S=1/2 EPR signals in the as isolated state and dithionite reduced state could be explained by the assumption that the 'prismane protein' had four redox states: the fully reduced [6Fe-6S] 3+state with the fingerprint prismane signal, an [6Fe-6S] 4+redox state with unknown spin state (S=0 or integer), the [6Fe-6S] 5+state with the molybdenum-like S=1/2 EPR signal and the fully oxidized [6Fe-6S] 6+redox state (S=0 or integer).The purification, chemical analysis and biochemical characterization of this 'prismane protein' are described in Chapter 4. The 'prismane' protein is a monomeric, cytoplasmic protein with a molecular mass of 52 kDa as estimated by sedimentation-equilibrium centrifugation. The protein contained 6.3±0.4 Fe and 6.2±0.7 S 2-per polypeptide. With polyclonal antibodies similar 'prismane' proteins were detected in Desulfovibrio vulgaris (Monticello) and Desulfovibrio desulfuricans (ATCC 27774). Using the N-terminal sequence and antibodies against this prismane protein Stokkermans and coworkers have sequenced the gene coding for this prismane protein as well as the homologous protein of Desulfovibrio desulfuricans (ATCC 27774).Further spectroscopic evidence for a new iron-sulfur cluster and strong support for the presence of a prismane core is presented in Chapter 5. The discovery that the [6Fe-6S] 5+redox state exhibited a spin mixture of approximately stoichiometric S=9/2 and substoichiometric molybdenum-like S=1/2 EPR signals confirmed the earlier hypothesis of four redox states of the prismane protein. Dye-mediated redox titrations and the observation of a g=16 signal with increased intensity in parallel-mode EPR for the [6Fe-6S] 4+redox state completed the following scheme:Multiple frequency EPR spectroscopy of the S=1/2 EPR signals showed that additional broadening indicative of nitrogen ligation was present. The line broadening caused by enrichment of the prismane protein with 57Fe was in agreement with ≈6 Fe per cluster. Quantitative high-resolution Mössbauer spectroscopy of the 57Fe enriched prismane protein revealed that both in the [6Fe-6S] 3+and the [6Fe-6S] 5+form the iron ions were inequivalent. A 4:2 ratio of quadrupole doublets was observed. The quadrupole splitting and isomer shift of the four irons ions were relatively invariant to the redox change of the cluster, while the two apparently more ionic irons had a more pronounced change from Fe 2+to Fe 3+character. Mössbauer spectroscopy at low temperatures and with applied magnetic fields indicated that the four and two iron ions were present in the same magnetically coupled structure. This led to a model in which the prismane structure is composed of a central set of four iron ions with a more ionic iron ion on each side. The more ionic iron ions could correlate with the nitrogen ligation as inferred from EPR studies.The unique EPR spectroscopic properties of the 'prismane protein' prompted investigation of dissimilatory sulfite reductase (desulfoviridin), a readily available iron-sulfur enzyme obtained during the isolation of Fe-hydrogenase from Desulfovibrio vulgaris (Hildenborough). The scrutiny for pure and electrophoretic homogeneous preparations of the desulfoviridin for EPR spectroscopic studies unexpectedly led to the discovery of a third, hitherto unrecognized 11 kDa subunit in this enzyme (Chapter 6). The γsubunit appeared to be tightly bound in the desulfoviridin complex for which a subunit composition of α 2β2γ2 was determined. N-terminal sequences and polyclonal antibodies against the α, βand γsubunits were obtained. The polyclonal antibodies allowed demonstration of the presence of homologous α, βand γsubunits in desulfoviridin-type dissimilatory sulfite reductases of three other Desulfovibrio species.Chapter 7 delineates the redox and spectroscopic results on the siroheme and S=9/2 EPR signals of desulfoviridin. By summation of the S=1/2 and S=5/2 EPR signals of the siroheme group it was shown that only 20% of the siroheme groups were metallated. The midpoint potential for the Fe 2+/Fe 3+transition of the main species of the siroheme was -295 mV. No significant amounts of EPR signals of normal iron-sulfur clusters were observed. Instead, several novel EPR signals with g= 17, g= 15. 1, g= 11.7 and g=9.0 were found in the as isolated oxidized form of the protein. These EPR signals were from a paramagnet with S=9/2. A stoichiometry of approximately 0.6 spin per αβγwas estimated. In a reductive redox titration the S=9/2 EPR signals disappeared with E m =-205 mV. It was proposed that in the desulfoviridin -type dissimilatory sulfite reductase larger iron-sulfur clusters are present which give rise to the S=9/2 EPR signals. The demetallation of the siroheme and the S=9/2 EPR signals from an iron-sulfur cluster were in contradiction with the model of Siegel and coworkers for the sulfite reductase of Escherichia coli, in which coupling between a regular [4Fe-4S] 2+cubane and the Fe 2+/3+ion of the siroheme is proposed to explain spectroscopic properties.In Chapter 8 the redox and EPR spectroscopic properties of the nitrogenase MoFe protein from Azotobacter vinelandii are described. By controlled oxidation with dye-mediated redox titrations the long lasting controversy on the spin and redox states of the oxidized P-cluster iron-sulfur centers was solved. It turned out that oxidation of the P clusters could lead to two consecutive redox states, P OX1and P OX2. On oxidation of the dithionite reduced P-clusters by two electrons (E m≈ -307 mV) first the P OX1state is obtained with a weak g=12 EPR signal, which increased in intensity at higher temperature and sharpened and intensified>10 fold in parallel- mode EPR. This allowed assignment of the g=12 EPR signal to an excited state of a non-Kramers spin system (presumably S=3). Previous Mössbauer and MCD spectroscopic measurements appeared to have been made with this redox state. A second oxidation by one electron (E m =+90 mV) led to the P OX2redox state, which occurred as a spin mixture of S=1/2 and S=7/2 species. This redox state corresponded to the form obtained by the solid thionine oxidation procedure of Hagen and coworkers. Further oxidation of P OX2redox state caused destruction of the iron-sulfur clusters and concommitant formation of S=9/2 and other high spin EPR signals.During the efforts to obtain highly-purified Fe-hydrogenase and prismane protein from Desulfovibrio vulgaris (Hildenborough) a black protein with an ultraviolet-visible spectrum reminiscent of rubredoxin-like iron-sulfur centers was obtained. Subsequent biochemical and EPR spectroscopic characterization (Chapter 9) indicated that this protein was similar but not identical to the protein rubrerythrin isolated by Moura and coworkers. The new protein was called nigerythrin due to its black color and hemerythrin-like EPR signal. Although rubrerythrin was originally reported to contain two rubredoxin-like and one dinuclear iron center, metal analyses and spin quantitation revealed that rubrerythrin and nigerythrin each contain two rubredoxin-like and two dinuclear iron centers per homodimer. The three redox transitions in both proteins had midpoint potentials higher than +200 mV. This suggested that both proteins have a non-redox role with all six iron ions in the ferrous state.In Chapter 10 a literature survey of non-integer and integer high spin systems in ironsulfur proteins is presented. In contrast to the well-documented occurrence of S=3/2 and S=2 spin states in [areas] 1+and [3Fe-4S] 0, respectively, the characterization of other, unusual iron-sulfur clusters with high spin states has not yet reached full maturity. The recent crystal structure of the MoFe protein of Azotobacter vinelandii, in which the FeMoco and P-clusters appeared to be larger clusters shows that the correlation between high spin states with structures other than the four basic iron-sulfur clusters indeed holds. The diversity of redox and spin states as observed for the prismane protein, desulfoviridin, carbonmonoxide dehydrogenase and Fe-hydrogenase indicates that besides the FeMoco and P-clusters other larger iron-sulfur clusters are present in biological systems
Flowering and vegetative propagation of pyrethrum (Chrysanthemum cinerariaefolium Vis.) in vivo and in vitro
No full textThe influence of climatic conditions was investigated on flowering behaviour of pyrethrum ( Chrysanthemum cinerariaefolium Vis.). At low temperatures high numbers of plants initiated high numbers of flower heads. Both the development of the initiated flower heads and the vegetative development of the plants were stimulated by higher temperatures.The second aspect was the development of methods of vegetative propagation in vivo and in vitro. Through a culture of peduncle explants in vitro detailed information was obtained about the initiation and development of adventitious roots. With these data the process of adventitious root formation of shoot cuttings in vivo was optimalized. In practice this method of vegetative propagation in vivo may be useful for a fast multiplication of selected healthy plants with high yields of pyrethrins. Vegetative propagation was also achieved by initiation and development of adventitious shoots on capitulum explants cultivated in vitro and subsequent adventitious root formation of detached shoots. This procedure was applicable for vegetative propagation of several other Compositae.</em
Cosmopolitanism in context: an introduction
No full textIs it possible and desirable to translate the basic principles underlying cosmopolitanism as a moral standard into effective global institutions. Will the ideals of inclusiveness and equal moral concern for all survive the marriage between cosmopolitanism and institutional power? What are the effects of such bureaucratisation of cosmopolitan ideals? This volume examines the strained relationship between cosmopolitanism as a moral standard and the legal institutions in which cosmopolitan norms and principles are to be implemented. Five areas of global concern are analysed: environmental protection, economic regulation, peace and security, the fight against international crimes and migration
Can Cosmopolitanism Survive Institutionalization?
No full textIs it possible and desirable to translate the basic principles underlying cosmopolitanism as a moral standard into effective global institutions. Will the ideals of inclusiveness and equal moral concern for all survive the marriage between cosmopolitanism and institutional power? What are the effects of such bureaucratisation of cosmopolitan ideals? This volume examines the strained relationship between cosmopolitanism as a moral standard and the legal institutions in which cosmopolitan norms and principles are to be implemented. Five areas of global concern are analysed: environmental protection, economic regulation, peace and security, the fight against international crimes and migration
Geomorfologische reconstructies van het oeverwallenlandschap in de Rijn-Maasdelta tijdens het eerste millennium na Chr.
No full textThis dataset contains landscape reconstructions of the Rhine-Meuse delta for the first millennium AD, which is the last millennium before large-scale river embankment. The dataset provides a detailed integrated reconstruction of the landscape of natural levees (alluvial ridges) and residual channel landforms throughout the delta (Pierik et al., 2017).
The palaeogeographical geomorphological reconstruction maps in this dataset were compiled for AD 100, 500 and AD 900. Furthermore, for AD 100 and 900 palaeoDEMs were made, storing a reconstruction of past surface elevation. The dataset has been compiled for the PhD thesis of Harm Jan Pierik (Pierik, 2017) within the project ‘The Dark Ages in an interdisciplinary light’ (www.darkagesproject.com; Jansma et al., 2014), funded by NWO (project nr. 360-60-110). The maps are made for analysis at superregional scale (e.g. Pierik et al., 2017). For smaller study areas they provide the context of the past landscape, to which local investigation (e.g. as part of archaeological prospective surveying) might well add further detail
BIODIVERSITY MANAGEMENT FOR INTEGRATING CONSERVATION AND PRODUCTION IN MODERN AGRICULTURAL SYSTEMS
No full textThe conservation of biodiversity is one of the primary concerns when dealing with agro-ecosystems, which other than providing food and fodder resources, can benefit of high levels of ecological functioning. The multifunctionality of agro-ecosystems has to be assessed in a multidisciplinary way and new methodologies should be developed to tackle it, at different spatial and temporal scales. The multi-scale approach is useful to delineate an overall view of the ecosystem and productive services of agricultural areas. This manuscript presents three researches dealing with the conservation of biodiversity, with a view to agricultural production, that were carried out in three different contexts of interest. Such a choice was intended to permit the application of new techniques and to adapt existing ones to different spatial and temporal scales.
The first context was chosen to delineate a new methodology for conserving semi-natural water resources in an highly fragmented landscape scenario, the district of Milan. In particular, one of the key elements of the territory is that of fontanili, semi-natural plain springs that represent both strong water resources for agriculture and the remnants of ancient green zones, but are more and more affected by urbanization rates and intensification of agricultural practices. They are listed as habitats for some endangered species, mainly aquatic, and conservation strategies are needed to preserve their ecosystem services. We chose to rely on landscape ecology analyses, which are able to assess how ecological corridors are structured between sources and sinks of biodiversity, represented by fontanili. We developed a new indicator, called Fuzzy Functionality Index (FFI), that for the first time collimates two of the more common types of analysis: the structural analysis of landscape fragmentation, and the assessment of species-specific permeability to movement. The index, resulting from a participative process, was at the basis of the spatial assessment of ecological corridors between fontanili and has proven to be highly effective and very flexible. It permits one to assemble geographic data, the knowledge of a multidisciplinary team and open source software to obtain a simple-to-read, mapped index at virtually no cost, eliding the issues of the traditional methods.
The second context is that of a rural livestock farming district at high altitudes, in the Alps of Northern Italy. Alpine meadows have been exposed to profound management shifts in modern times: changes in plant species composition and biodiversity losses are widespread issues. The aim of the work was to inspect how the variability of meadows could be explainable by the environment they depend on and by the management strategies applied. We analyzed the plant species composition, biodiversity and forage value of meadows in the context and their relationships with environmental and management variables, collected among the farmers. The management variables explained a small amount of variance: only the number of cuts per year remarkably explained the plant species composition and biodiversity. The number of cattle and the field applied nitrogen only described the most intensively managed communities. The environmental variables better described the variability of responses: in particular, an increase of the Landolt Nutrient Index was associated with an increase of the forage value opposite to a decrease of the Shannon Index. The negative correlation between the two responses highlights a known dilemma referring to high altitude meadow communities, which are subjected to important environmental constraints. Some taxa as Anthriscus sylvestris, Heracleum sphondylium, Rumex acetosa and Polygonum bistorta were found to critically unbalance the species composition thus the overall biodiversity. This is certainly the most critical finding, explainable by the late first cuts commonly adopted and by long-term intensive management choices. Homologated management strategies could not explain the wide ecological variability investigated, but indeed they made possible to understand how the system should be deeply revised, in respect to limiting environmental constraints and fodder capabilities at high altitudes.
The third context is that of an agronomic field experiment carried out over a long period. The work compares biomass, Milk Feed Units (MFU) and Crude Proteins (CP) yields, over a period of 21 years (1986-2006), referring to five fodder cropping systems: (i) a one-year double-crop rotation (R1) of autumn-sown Italian ryegrass + spring-sown silage maize; (ii) a three-year rotation (R3) of grain maize (first year), autumn-sown barley + silage maize (second year), and Italian ryegrass + silage maize (third year); (iii) a six-year rotation (R6) of Italian ryegrass + silage maize (years 1,2,3) + mixed meadow of white clover and tall fescue (years 4,5,6); (iv) a continuous grain maize (CM); and (v) a permanent meadow (PM). All cropping systems were subjected to two levels of agronomic inputs: high (A), indicating the amounts of fertilizers and herbicides normally applied by farmers in the region, and low (B) consisting in reduced amounts of fertilizers (-30%) and herbicide rates (-25%) compared to A. We found R1 > R3 > R6 > PM > CM in terms of biomass yields, with a slightly different trend for MFU yields, whereas R6 > R1 > PM > R3 > CM regarding CP yields. The two treatments always resulted A > B. The five cropping systems significantly varied between the 21 years of experiment: all of them showed decreasing performances except for PM, improving in biomass, MFU and CP over time. The three rotations (R1, R3, R6) appeared the most stable cropping systems over time. These findings suggest the importance of complex cropping systems, which could provide high quality of fodder besides guaranteeing a remarkable agricultural diversification
Meadows species composition, biodiversity and forage value in an Alpine district : Relationships with environmental and dairy farm management variables
No full textAlpine meadows have been exposed to relevant management shifts in the last decades, with changes in plant species composition and biodiversity losses often occurring in favor of augmented foraging capabilities, especially in marginal rural contexts. In this study, we analyzed the relationships among the plant species composition, biodiversity and forage value of meadows and two sets of variables, environmental and management ones, in a dairy district of the Central Italian Alps. Results indicate that management variables could only explain limited variability of the meadows under study: for instance, the number of cuts per year is available to justify the plant species composition and biodiversity of such coenoses. Moreover, the environmental variables better described the variability of responses, due to the harsh environmental constraints of the area under examination, located at high altitudes. The shared effects of the two sets explained larger variance than the management set alone, due to the complex relationships of environmental and management factors in the context. The forage value of meadows, an indicator of hay quality, was found negatively associated with the Shannon Index. This behavior highlights a known dilemma which especially refers to high altitude communities as the ones under study, clearly highlighting trade-offs between their production and biodiversity. Some taxa as Anthriscus sylvestris, Heracleum sphondylium and others critically unbalance the species composition of meadows, thus their overall biodiversity, at low altitudes. This finding, explainable by the late first cuttings commonly adopted by all farmers, suggests the eutrophication of coenoses. The management choices inspected did not reflect on the wide variability of meadows, but indeed they made possible to understand how this farming system should be deeply revised, with respect to environmental constraints and meadows’ fodder capabilities
Connection between secondary agricultural education and labour market 1990
No full textTwo cohorts of students finished their secondary agricultural education (MAO) in the years 1978 and 1987 were traced and they were asked to evaluate their education and their career. Agricultural background / preliminary training / residence of MAO / subject / importance of fields of study in present job / attention paid to fields of study and practical skills during MAO / daytime education and courses after MAO of importance for career / need for courses and training at the moment / informed about courses and training of the MAO / has planned to follow courses in the near future, and motivation / description of present function and additional functions: activities, independence, had enough education to do job well, hierarchical level, education of leader, number of employees of company, expectations of employment in future for company, preference for full-time or part-time job, ( not ) satisfied with aspects of job ( level, promotion, work load, circumstances, scope to develop, working hours, income ), how did respondent get present job / has been unemployed involuntary after MAO / description of functions after MAO, before present function / most important cause of not having a paid job / social benefit / chances for paid job in near future / self-employed entrepreneurship / informed about vacancies / time spending on housekeeping and voluntary work / expectations about future of agriculture Background variables: basic characteristics/ household characteristics/ occupation/employment/ income/capital assets/ education/ readership, mass media, and 'cultural' exposur
Stereochemistry of the methyl group in (R)-3-methylitaconate derived by rearrangement of 2-methylideneglutarate catalysed by a coenzyme B-12-dependent mutase
No full text2-Methylidenegtutarate mutase is an adenosylcobalamin (coenzyme B-12)-dependent enzyme that catalyses the equilibration of 2-methylideneglutarate with (R)-3-methylitaconate. This reaction is believed to occur via protein-bound free radicals derived from substrate and product. The stereochemistry of the formation Of the methyl group of 3-mechylitaconate has been probed using a 'chiral methyl group'. The methyl group in 3-([H-2(1),H-3]methyl)itaconate derived from either (R)- or (S)-2-methylidene[3-H-2(1),3-H-3(1)]glutarate was a 50:50 mixture of (R)- and (S)-forms. It is concluded that the barrier to rotation about the C-C bond between the methylene radical centre and adjacent C-atom in the product-related radical [(CH)-C-.,CH(-O2CC=CH2)CO2-] is relatively low, and that the interaction of the radical with cob(II)alamin is minimal. Hence, cob(II)alamin is a spectator of the molecular rearrangement of the substrate radical to product radical
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