Cluster size dependent coordination of formate to free manganese oxide clusters.

The interaction of free manganese oxide clusters, MnO ( = 1-9, = 0-12), with formic acid was studied infrared multiple-photon dissociation (IR-MPD) spectroscopy together with calculations using density functional theory (DFT). Clusters containing only one Mn atom, such as MnO and MnO, bind formic acid as an intact molecule in both the - and -configuration. In contrast, all clusters containing two or more manganese atoms deprotonate the acid's hydroxyl group.

Constraining the contribution of the Antarctic Ice Sheet to Last Interglacial sea level.

Polar temperatures during the Last Interglacial [LIG; ~129 to 116 thousand years (ka)] were warmer than today, making this time period an important testing ground to better understand how ice sheets respond to warming. However, it remains debated how much and when the Antarctic and Greenland ice sheets changed during this period. Here, we present a combination of new and existing absolutely dated LIG sea-level observations from Britain, France, and Denmark.

Spin-Gated Selectivity of the Water Oxidation Reaction Mediated by Free Pentameric CaMnO Clusters.

We report on the first preparation of isolated ligand-free CaMnO gas-phase clusters, as well as other pentameric CaMnO ( = 0-4) clusters with varying Ca contents, which serve as molecular models of the natural CaMnO inorganic cluster in photosystem II. Ion trap reactivity studies with DO and HO reveal a pronounced cluster composition-dependent ability to mediate the oxidation of water to hydrogen peroxide. First-principles density functional theory simulations elucidate the mechanism of water oxidation, proceeding via formation of a terminal oxyl radical followed by oxyl/hydroxy (O/OH) coupling.

Low-salinity transitions drive abrupt microbial response to sea-level change.

The salinisation of many coastal ecosystems is underway and is expected to continue into the future because of sea-level rise and storm intensification brought about by the changing climate. However, the response of soil microbes to increasing salinity conditions within coastal environments is poorly understood, despite their importance for nutrient cascading, carbon sequestration and wider ecosystem functioning. Here, we demonstrate deterioration in the productivity of a top-tier microbial group (testate amoebae) with increasing coastal salinity, which we show to be consistent across phylogenetic groups, salinity gradients, environment types and latitude.

Size, Stoichiometry, Dimensionality, and Ca Doping of Manganese Oxide-Based Water Oxidation Clusters: An Oxyl/Hydroxy Mechanism for Oxygen-Oxygen Coupling.

Gas-phase ion-trap reactivity experiments and density functional simulations reveal that water oxidation to HO mediated by (calcium) manganese oxide clusters proceeds via formation of a terminal oxyl radical followed by oxyl/hydroxy O-O coupling. This mechanism is predicted to be energetically feasible for MnO ( = 2-4) and the binary CaMnO, in agreement with the experimental observations. In contrast, the reaction does not proceed for the tetramanganese oxides MnO ( = 4-6) under these experimental conditions.

Cluster Size Dependent Interaction of Free Manganese Oxide Clusters with Acetic Acid and Methyl Acetate.

We have employed infrared multiple-photon dissociation (IR-MPD) spectroscopy together with density functional theory (DFT) calculations to study the interaction of series of subnanometer sized manganese oxide clusters, MnO ( = 1-6, = 0-9) with acetic acid (HOAc) and methyl acetate (MeOAc). Reaction with HOAc leads to strongly cluster size and composition dependent IR-MPD spectra, indicating molecular adsorption on MnO clusters and thermodynamically favorable but kinetically hampered HOAc dissociation (deprotonation) on MnO and MnO. Other cluster sizes exhibit the preferred formation of a dissociative bidentate chelating structure.

Rest tremor correlates with reduced contralateral striatal dopamine transporter binding in Parkinson's disease.

Introduction: In vivo dopamine transporter imaging is a useful tool for distinguishing nigrostriatal pathologies (e.g. Parkinson's disease) from other causes of tremor.

Nonlinear landscape and cultural response to sea-level rise.

Rising sea levels have been associated with human migration and behavioral shifts throughout prehistory, often with an emphasis on landscape submergence and consequent societal collapse. However, the assumption that future sea-level rise will drive similar adaptive responses is overly simplistic. While the change from land to sea represents a dramatic and permanent shift for preexisting human populations, the process of change is driven by a complex set of physical and cultural processes with long transitional phases of landscape and socioeconomic change.

Carbide Dihydrides: Carbonaceous Species Identified in Ta -Mediated Methane Dehydrogenation.

The products of methane dehydrogenation by gas-phase Ta clusters are structurally characterized using infrared multiple photon dissociation (IRMPD) spectroscopy in conjunction with quantum chemical calculations. The obtained spectra of [4Ta,C,2H] reveal a dominance of vibrational bands of a H Ta C carbide dihydride structure over those indicative for a HTa CH carbyne hydride one, as is unambiguously verified by studies employing various methane isotopologues. Because methane dehydrogenation by metal cations M typically leads to the formation of either MCH carbene or HMCH carbyne hydride structures, the observation of a H MC carbide dihydride structure implies that it is imperative to consider this often-neglected class of carbonaceous intermediates in the reaction of metals with hydrocarbons.

Comparative Assessments of Left and Right Ventricular Function by Two-Dimensional, Contrast Enhanced and Three-Dimensional Echocardiography with Gated Heart Pool Scans in Patients Following Myocardial Infarction.

Multiple noninvasive imaging modalities are available to measure biventricular function, although limited studies have assessed agreement between modalities in assessing left and right ventricular ejection fraction (LVEF & RVEF) in the same cohort of patients. In this study we prospectively compared the agreement of 2-dimensional echocardiography (2DE), contrast enhanced 2DE, 3-dimensional echocardiography (3DE), and gated heart pool scan (GHPS) measures of LVEF and RVEF in patients with acute ST-elevation myocardial infarction. We recruited 95 consecutive ST-elevation myocardial infarction patients (mean age 61.

Energetic Stabilization of Carboxylic Acid Conformers by Manganese Atoms and Clusters.

Free cationic manganese atoms and clusters Mn ( = 1-3) have been reacted with small carboxylic acids (formic, acetic, and propionic acids) and methyl acetate in a flow tube reactor held at room temperature. The geometry of the thus formed complexes has subsequently been studied via infrared multiple-photon dissociation (IR-MPD) spectroscopy and density-functional theory (DFT) calculations. The IR-MPD spectra of the acid complexes show two signals in the C═O stretch region indicating the coexistence of two conformers.

Infrared Spectroscopy of Gas-Phase MnO(CO) Complexes.

The interaction of manganese oxide clusters MnO ( = 2-5, ≥ ) with CO is studied via infrared multiple-photon dissociation spectroscopy (IR-MPD) in the spectral region of 630-1860 cm. Along with vibrational modes of the manganese oxide cluster core, two bands are observed around 1200-1450 cm and they are assigned to the characteristic Fermi resonance of CO arising from anharmonic coupling between the symmetric stretch vibration and the overtone of the bending mode. The spectral position of the lower frequency band depends on the cluster size and the number of adsorbed CO molecules, whereas the higher frequency band is largely unaffected.

Disruption of Membrane Integrity by the Bacterium-Derived Antifungal Jagaricin.

Jagaricin is a lipopeptide produced by the bacterial mushroom pathogen , the causative agent of mushroom soft rot disease. Apart from causing lesions in mushrooms, jagaricin is a potent antifungal active against human-pathogenic fungi. We show that jagaricin acts by impairing membrane integrity, resulting in a rapid flux of ions, including Ca, into susceptible target cells.

A Gas-Phase Ca Mn O Cluster Model for the Oxygen-Evolving Complex of Photosystem II.

One of the fundamental processes in nature, the oxidation of water, is catalyzed by a small CaMn O ⋅MnO cluster located in photosystem II (PS II). Now, the first successful preparation of a series of isolated ligand-free tetrameric Ca Mn O (n=0-4) cluster ions is reported, which are employed as structural models for the catalytically active site of PS II. Gas-phase reactivity experiments with D O and H O in an ion trap reveal the facile deprotonation of multiple water molecules via hydroxylation of the cluster oxo bridges for all investigated clusters.

The legacy of 4,500 years of polyculture agroforestry in the eastern Amazon.

The legacy of pre-Columbian land use in the Amazonian rainforest is one of the most controversial topics in the social and natural sciences. Until now, the debate has been limited to discipline-specific studies, based purely on archaeological data, modern vegetation, modern ethnographic data or a limited integration of archaeological and palaeoecological data. The lack of integrated studies to connect past land use with modern vegetation has left questions about the legacy of pre-Columbian land use on the modern vegetation composition in the Amazon, unanswered.

The Chemoattractant Glorin Is Inactivated by Ester Cleavage during Early Multicellular Development of Polysphondylium pallidum.

Among the amoebozoan species capable of forming fruiting bodies, the dictyostelid social amoebae stand out since they form true multicellular organisms by means of single cell aggregation. Upon food depletion, cells migrate across gradients of extracellular signals initiated by cells in aggregation centers. The model species that is widely used to study multicellular development of social amoebae, Dictyostelium discoideum, uses cyclic adenosine monophosphate (cAMP) as a chemoattractant to coordinate aggregation.

Thermal stability of iron-sulfur clusters.

The thermal decomposition of free cationic iron-sulfur clusters FeS (x = 0-7, y = 0-9) is investigated by collisional post-heating in the temperature range between 300 and 1000 K. With increasing temperature the preferential formation of stoichiometric FeS (y = x) or near stoichiometric FeS (y = x ± 1) clusters is observed. In particular, FeS represents the most abundant product up to 600 K, FeS and FeS are preferably formed between 600 K and 800 K, and FeS clearly dominates the cluster distribution above 800 K.

Respiratory Motion Compensation for PET/CT with Motion Information Derived from Matched Attenuation-Corrected Gated PET Data.

Respiratory motion degrades the detection and quantification capabilities of PET/CT imaging. Moreover, mismatch between a fast helical CT image and a time-averaged PET image due to respiratory motion results in additional attenuation correction artifacts and inaccurate localization. Current motion compensation approaches typically have 3 limitations: the mismatch among respiration-gated PET images and the CT attenuation correction (CTAC) map can introduce artifacts in the gated PET reconstructions that can subsequently affect the accuracy of the motion estimation; sinogram-based correction approaches do not correct for intragate motion due to intracycle and intercycle breathing variations; and the mismatch between the PET motion compensation reference gate and the CT image can cause an additional CT-mismatch artifact.

Natural Products from Social Amoebae.

Natural products are invaluable sources of structural diversity and complexity ideally suited for the development of therapeutic agents. The search for novel bioactive molecules has prompted scientists to explore various ecological niches. Microorganisms have been shown to constitute such an important source.

Selective C-H Bond Cleavage in Methane by Small Gold Clusters.

Methane represents the major constituent of natural gas. It is primarily used only as a source of energy by means of combustion, but could also serve as an abundant hydrocarbon feedstock for high quality chemicals. One of the major challenges in catalysis research nowadays is therefore the development of materials that selectively cleave one of the four C-H bonds of methane and thus make it amenable for further chemical conversion into valuable compounds.

Structure, Biosynthesis, and Biological Activity of the Cyclic Lipopeptide Anikasin.

The class of cyclic lipopeptide natural products consists of compounds with a diverse range of bioactivities. In this study, we elucidated the structure of the cyclic lipopeptide anikasin using X-ray crystallography, analyzed its biosynthetic gene cluster, and investigated its natural role in the interaction between the producer strain Pseudomonas fluorescens HKI0770 and protozoal predators. These results led to the conclusion that anikasin has dual functionality enabling swarming motility and acting as a niche amoebicide, which effectively inhibits the social amoeba Polysphondylium violaceum and protects the producer strain from protozoal grazing.

Lysinibacillus fusiformis M5 Induces Increased Complexity in Bacillus subtilis 168 Colony Biofilms via Hypoxanthine.

In recent years, biofilms have become a central subject of research in the fields of microbiology, medicine, agriculture, and systems biology, among others. The sociomicrobiology of multispecies biofilms, however, is still poorly understood. Here, we report a screening system that allowed us to identify soil bacteria which induce architectural changes in biofilm colonies when cocultured with We identified the soil bacterium M5 as an inducer of wrinkle formation in colonies mediated by a diffusible signaling molecule.

Versatile synthesis of the signaling peptide glorin.

We present a versatile synthesis of the eukaryotic signaling peptide glorin as well as glorinamide, a synthetic analog. The ability of these compounds to activate glorin-induced genes in the social amoeba was evaluated by quantitative reverse transcription PCR, whereby both compounds showed bioactivity comparable to a glorin standard. This synthetic route will be useful in conducting detailed structure-activity relationship studies as well as in the design of chemical probes to dissect glorin-mediated signaling pathways.

Confirmation of a de novo structure prediction for an atomically precise monolayer-coated silver nanoparticle.

Fathoming the principles underpinning the structures of monolayer-coated molecular metal nanoparticles remains an enduring challenge. Notwithstanding recent x-ray determinations, coveted veritable de novo structural predictions are scarce. Building on recent syntheses and de novo structure predictions of Au Ag (TBBT), where is a countercation, = 0 or 1, and TBBT is 4--butylbenzenethiol, we report an x-ray-determined structure that authenticates an a priori prediction and, in conjunction with first-principles theoretical analysis, lends force to the underlying forecasting methodology.