316 research outputs found
Utopien der Revolution: Von der Erschaffung des Neuen Menschen zur Eroberung des Weltraums
No full textUtopien der Revolution : von der Erschaffung des Neuen Menschen zur Eroberung des Weltraums
No full textSeawater salinity sample measurements from the Antarctic Circumnavigation Expedition (ACE)
No full textDataset abstract
This data set contains salinity measurements from discrete seawater samples that were collected in the Southern Ocean (south of 30deg S) during the Antarctic Circumnavigation Expedition (ACE). 657 samples were collected during the period December 24th, 2016 and March 18th, 2017 in the Southern Ocean from the surface ocean using the ship's underway line (UW; 328 samples) and in vertical profiles using Niskin bottles mounted on the CTD rosette (273 samples). A few additional samples (56) were collected from a parallel cast with a trace-metal rosette, with a bucket, and as duplicates to ensure data quality. All samples were analyzed for their salinity and results are reported on the Practical Salinity Scale 1978 (PSS-78; Sea-Bird Electronics, Inc., 1989). Measurements were performed on a Guildline Autosal Laboratory Salinometer 8400(B) at CSIRO (Hobart, Australia) for samples collected during leg 1, and on a OPTIMARE Precision Salinometer (OPS) at the Alfred Wegener Institute (Bremerhaven, Germany) for samples collected during legs 2 and 3. This circumpolar data set provides insights into the hydrological cycle of the Southern Ocean and the processes (precipitation, evaporation, sea-ice melting and freezing, ice-berg and land-ice melting) that determine the salinity of a certain water mass. It is being used to calibrate the CTD sensor vertical profiles (Henry et al., 2020) and thermosalinograph sensor underway measurements (Haumann et al., 2020) from the ACE cruise.
Dataset contents
Processed Data
ace_18_data_salinity_ctd_20200812.csv, text format; contains salinity measurements of seawater samples collected from the Niskin bottles mounted on the CTD rosette
ace_18_data_salinity_uw_20200812.csv, text format; contains salinity measurements of seawater samples collected from the underway line
ace_18_data_salinity_other_20200812.csv, text format; contains salinity measurements of miscellaneous samples: Duplicate seawater samples; seawater bucket sample from Cumberland Bay, South Georgia; seawater samples from Niskin bottles mounted on the trace-metal rosette.
Metadata
data_file_header.txt, metadata, text format
README.txt, metadata, text format
figure*.pdf, metadata, portable document format
Dataset license
This physical and biogeochemical oceanography dataset is made available under the Creative Commons Attribution 4.0 License (CC BY 4.0) whose full text can be found at https://creativecommons.org/licenses/by/4.0/This research was supported by Swiss National Science Foundation (SNSF) grant numbers PZ00P2_142684, P2EZP2_175162, and P400P2_186681, and a grant from the BNP Paribas Foundation. I.G. thanks FCT/ MCTES for the financial support to CESAM (UIDP/50017/2020+UIDB/50017/2020) through national funds. We thank Kendall Sherrin (CSIRO) for processing the leg 1 samples, and Susan Becker and Lynne Talley (Scripps) for lending us their sampling bottles. We thank Stefan Vogel for the Autosal cleaning/checking and logistics in Hobart and Gwenael Renard for assistance with samples/cargo handling in Bremerhaven. We thank Yvonne Firing and Rob Craft (NOC) for providing Autosal training. It would have not been possible to assemble this data set without their help. The Antarctic Circumnavigation Expedition was made possible by funding from the Swiss Polar Institute and Ferring Pharmaceuticals
Eight steps preceding O–O bond formation in oxygenic photosynthesis—A basic reaction cycle of the Photosystem II manganese complex
No full textAbstractIn oxygenic photosynthesis, water is split at a Mn4Ca complex bound to the proteins of photosystem II (PSII). Powered by four quanta of visible light, four electrons and four protons are removed from two water molecules before dioxygen is released. By this process, water becomes an inexhaustible source of the protons and electrons needed for primary biomass formation. On the basis of structural and spectroscopic data, we recently have introduced a basic reaction cycle of water oxidation which extends the classical S-state cycle [B. Kok, B. Forbush, M. McGloin, Cooperation of charges in photosynthetic O2 evolution- I. A linear four-step mechanism, Photochem. Photobiol. 11 (1970) 457–475] by taking into account also the role and sequence of deprotonation events [H. Dau, M. Haumann, Reaction cycle of photosynthetic water oxidation in plants and cyanobacteria, Science 312 (2006) 1471–1472]. We propose that the outwardly convoluted and irregular events of the classical S-state cycle are governed by a simple underlying principle: protons and electrons are removed strictly alternately from the Mn complex. Starting in I0, eight successive steps of alternate proton and electron removal lead to I8 and only then the O–O bond is formed. Thus not only four oxidizing equivalents, but also four bases are accumulated prior to the onset of dioxygen formation. After reviewing the kinetic properties of the individual S-state transition, we show that the proposed basic model explains a large body of experimental results straightforwardly. Furthermore we discuss how the I-cycle model addresses the redox-potential problem of PSII water oxidation and we propose that the accumulated bases facilitate dioxygen formation by acting as proton acceptors
Evidence for impaired hydrogen-bonding of tyrosine YZ in calcium-depleted Photosystem II
No full textAbstractPhotosystem II (PS II) evolves oxygen from two bound water molecules in a four-stepped reaction that is driven by four quanta of light, each oxidizing the chlorophyll moiety P680 to yield P+680. When starting from its dark equilibrium (mainly state S1), the catalytic center can be clocked through its redox states (S0…S4) by a series of short flashes of light. The center involves at least a Mn4-cluster and a special tyrosine residue, named YZ, as redox cofactors plus two essential ionic cofactors, Cl− and Ca2+. Centers which have lost Ca2+ do not evolve oxygen. We investigated the stepped progression in dark-adapted PS II core particles after the removal of Ca2+. YZ was oxidized from the first flash on. The difference spectrum of YZ→YoxZ differed from the one in competent centers, where it has been ascribed to a hydrogen-bonded tyrosinate. The rate of the electron transfer from YZ to P+680 was slowed down by three orders of magnitude and its kinetic isotope effect rose up from 1.1 to 2.5. Proton release into the bulk was now a prerequisite for the electron transfer from YZ to P+680. On the basis of these results and similar effects in Mn-(plus Ca2+-)depleted PS II (M. Haumann et al., Biochemistry, 38 (1999) 1258–1267) we conclude that the presence of Ca2+ in the catalytic center is required to tune the apparent pK of a base cluster, B, to which YZ is linked by hydrogen bonds. The deposition of a proton on B within close proximity of YZ (not its release into the bulk!) is a necessary condition for the reduction in nanoseconds of P+680 and for the functioning of water oxidation. The removal of Ca2+ rises the pK of B, thereby disturbing the hydrogen bonded structure of YZB
Iron–molybdenum-oxo complexes as initiators for olefin autoxidation with O2
No full textThe reaction between [(TPA)Fe(MeCN)2](OTf)2 and [nBu4N](Cp*MoO3) yields the
novel tetranuclear complex [(TPA)Fe(μ-Cp*MoO3)]2(OTf)2, 1, with a rectangular
[Mo–O–Fe–O–]2 core containing high-spin iron(II) centres. 1 proved to be an
efficient initiator/(pre)catalyst for the autoxidation of cis-cyclooctene with
O2 to give cyclooctene epoxide. To test, which features of 1 are essential in
this regard, analogues with zinc(II) and cobalt(II) central atoms, namely
[(TPA)Zn(Cp*MoO3)](OTf), 3, and [(TPA)Co(Cp*MoO3)](OTf), 4, were prepared,
which proved to be inactive. The precursor compounds of 1,
[(TPA)Fe(MeCN)2](OTf)2 and [nBu4N](Cp*MoO3) as well as Cp2*Mo2O5, were found
to be inactive, too. Reactivity studies in the absence of cyclooctene revealed
that 1 reacts both with O2 and PhIO via loss of the Cp* ligands to give the
triflate salt 2 of the known cation [((TPA)Fe)2(μ-O)(μ-MoO4)]2+. The cobalt
analogue 4 reacts with O2 in a different way yielding
[((TPA)Co)2(μ-Mo2O8)](OTf)2, 5, featuring a Mo2O84− structural unit which is
novel in coordination chemistry. The compound [(TPA)Fe(μ-MoO4)]2, 6, being
related to 1, but lacking Cp* ligands failed to trigger autoxidation of
cyclooctene. However, initiation of autoxidation by Cp* radicals was excluded
via experiments including thermal dissociation of Cp2*
SCALMS: Liquid Metal Catalysis with Ternary Alloys, Enhancing Activity in Propane Dehydrogenation
No full text<p>All data used for the publication: </p>
<p><strong>Supported Catalytically Active Liquid Metal Solutions: Liquid Metal Catalysis with Ternary Alloys, Enhancing Activity in Propane Dehydrogenation</strong></p>
<p>Michael Moritz, Sven Maisel, Narayanan Raman, Haiko Wittkämper, Christoph Wichmann, Mathias Grabau, Deniz Kahraman, Julien Steffen, Nicola Taccardi, Andreas Görling, Marco Haumann, Peter Wasserscheid, Hans-Peter Steinrück, and Christian Papp*</p>
<p>https://doi.org/10.1021/acscatal.4c01282</p>
From random to regular: Neural constraints on the emergence of isochronous rhythm during cultural transmission
No full textA core design feature of human communication systems and expressive behaviours is their temporal organization. The cultural evolutionary origins of this feature remain unclear. Here, we test the hypothesis that regularities in the temporal organization of signalling sequences arise in the course of cultural transmission as adaptations to aspects of cortical function. We conducted two experiments on the transmission of rhythms associated with affective meanings, focusing on one of the most widespread forms of regularity in language and music: isochronicity. In the first experiment, we investigated how isochronous rhythmic regularities emerge and change in multigenerational signalling games, where the receiver (learner) in a game becomes the sender (transmitter) in the next game. We show that signalling sequences tend to become rhythmically more isochronous as they are transmitted across generations. In the second experiment, we combined electroencephalography (EEG) and two-player signalling games over 2 successive days. We show that rhythmic regularization of sequences can be predicted based on the latencies of the mismatch negativity response in a temporal oddball paradigm. These results suggest that forms of isochronicity in communication systems originate in neural constraints on information processing, which may be expressed and amplified in the course of cultural transmission.publishedVersion© The Author(s) (2018). Published by Oxford University Press. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact [email protected]
Structure of the Molybdenum Site in YedY, a Sulfite Oxidase Homologue from <i>Escherichia coli</i>
No full textYedY from Escherichia coli is a new member of the sulfite oxidase family of molybdenum cofactor (Moco)-containing oxidoreductases. We investigated the atomic structure of the molybdenum site in YedY by X-ray absorption spectroscopy, in comparison to human sulfite oxidase (hSO) and to a MoIV model complex. The K-edge energy was indicative of MoV in YedY, in agreement with X-and Q-band electron paramagnetic resonance results, whereas the hSO protein contained MoVI. In YedY and hSO, molybdenum is coordinated by two sulfur ligands from the molybdopterin ligand of the Moco, one thiolate sulfur of a cysteine (average Mo-S bond length of∼2.4 A), and one (axial) oxo ligand (Mo=O,∼1.7 A). hSO contained a second oxo group at Mo as expected, but in YedY, two species in about a 1:1 ratio were found at the active site, corresponding to an equatorial Mo-OH bond (∼2.1 A) or possibly to a shorter Mo-O-bond. Yet another oxygen (or nitrogen) at a∼2.6 A distance to Mo in YedY was identified, which could originate from a water molecule in the substrate binding cavity or from an amino acid residue close to the molybdenum site, i.e., Glu104, that is replaced by a glycine in hSO, or Asn45. The addition of the poor substrate dimethyl sulfoxide to YedY left the molybdenum coordination unchanged at high pH. In contrast, we found indications that the better substrate trimethylamine N-oxide and the substrate analogue acetone were bound at a∼2.6 Ã distance to the molybdenum, presumably replacing the equatorial oxygen ligand. These findings were used to interpret the recent crystal structure of YedY and bear implications for its catalytic mechanism
A crystallographic and Mo K-edge XAS study of molybdenum oxo bis-, mono-, and non-dithiolene complexes : first-sphere coordination geometry and noninnocence of ligands
No full textTen square-based pyramidal molybdenum complexes with different sulfur donor ligands, that is, a variety of dithiolenes and sulfides, were prepared, which mimic coordination motifs of the molybdenum cofactors of molybdenum-dependent oxidoreductases. The model compounds were investigated by Mo K-edge X-ray absorption spectroscopy (XAS) and (with one exception) their molecular structures were analyzed by X-ray diffraction to derive detailed information on bond lengths and geometries of the first coordination shell of molybdenum. Only small variations in Mo=O and Mo-S bond lengths and their respective coordination angles were observed for all complexes including those containing Mo(CO) 2 or Mo(μ-S)2Mo motifs. XAS analysis (edge energy) revealed higher relative oxidation levels in the molybdenum ion in compounds with innocent sulfur-based ligands relative to those in dithiolene complexes, which are known to exhibit noninnocence, that is, donation of substantial electron density from ligand to metal. In addition, longer average Mo-S and Mo=O bonds and consequently lower ν(Mo=O) stretching frequencies in the IR spectra were observed for complexes with dithiolene-derived ligands. The results emphasize that the noninnocent character of the dithiolene ligand influences the electronic structure of the model compounds, but does not significantly affect their metal coordination geometry, which is largely determined by the Mo(IV) or (V) ion itself. The latter conclusion also holds for the molybdenum site geometries in the oxidized MoVI cofactor of DMSO reductase and the reduced MoIV cofactor of arsenite oxidase. The innocent behavior of the dithiolene molybdopterin ligands observed in the enzymes is likely to be related to cofactor-protein interactions
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