Interpretation of X-ray Absorption Spectroscopy in the Presence of Surface Hybridization

X-ray absorption spectroscopy yields direct access to the electronic and geometric structure of hybrid inorganic-organic interfaces formed upon adsorption of complex molecules at metal surfaces. The unambiguous interpretation of corresponding spectra is challenged by the intrinsic geometric flexibility of the adsorbates and the chemical interactions with the interface. Density-functional theory (DFT) calculations of the extended adsorbate-substrate system are an established tool to guide peak assignment in X-ray photoelectron spectroscopy (XPS) of complex interfaces. We extend this to the simulation and interpretation of X-ray absorption spectroscopy (XAS) data in the context of functional organic molecules on metal surfaces using dispersion-corrected DFT calculations within the transition potential approach. On the example of X-ray absorption signatures for the prototypical case of 2H-porphine adsorbed on Ag(111) and Cu(111) substrates, we follow the two main effects of the molecule/surface interaction on XAS: (1) the substrate-induced chemical shift of the 1s core levels that dominates in physisorbed systems and (2) the hybridization-induced broadening and loss of distinct resonances that dominates in more chemisorbed systems.Comment: 13 pages, 4 figure

Spin Manipulation by Creation of Single-Molecule Radical Cations

All-trans-retinoic acid (ReA), a closed-shell organic molecule comprising only C, H, and O atoms, is investigated on a Au(111) substrate using scanning tunneling microscopy and spectroscopy. In dense arrays single ReA molecules are switched to a number of states, three of which carry a localized spin as evidenced by conductance spectroscopy in high magnetic fields. The spin of a single molecule may be reversibly switched on and off without affecting its neighbors. We suggest that ReA on Au is readily converted to a radical by the abstraction of an electron.Comment: 5 pages, 3 figures, accepted for publication in Phys. Rev. Let

Control of Gastric H,K-ATPase Activity by Cations, Voltage and Intracellular pH Analyzed by Voltage Clamp Fluorometry in Xenopus Oocytes

Whereas electrogenic partial reactions of the Na,K-ATPase have been studied in depth, much less is known about the influence of the membrane potential on the electroneutrally operating gastric H,K-ATPase. In this work, we investigated site-specifically fluorescence-labeled H,K-ATPase expressed in Xenopus oocytes by voltage clamp fluorometry to monitor the voltage-dependent distribution between E1P and E2P states and measured Rb+ uptake under various ionic and pH conditions. The steady-state E1P/E2P distribution, as indicated by the voltage-dependent fluorescence amplitudes and the Rb+ uptake activity were highly sensitive to small changes in intracellular pH, whereas even large extracellular pH changes affected neither the E1P/E2P distribution nor transport activity. Notably, intracellular acidification by approximately 0.5 pH units shifted V0.5, the voltage, at which the E1P/E2P ratio is 50∶50, by −100 mV. This was paralleled by an approximately two-fold acceleration of the forward rate constant of the E1P→E2P transition and a similar increase in the rate of steady-state cation transport. The temperature dependence of Rb+ uptake yielded an activation energy of ∼90 kJ/mol, suggesting that ion transport is rate-limited by a major conformational transition. The pronounced sensitivity towards intracellular pH suggests that proton uptake from the cytoplasmic side controls the level of phosphoenzyme entering the E1P→E2P conformational transition, thus limiting ion transport of the gastric H,K-ATPase. These findings highlight the significance of cellular mechanisms contributing to increased proton availability in the cytoplasm of gastric parietal cells. Furthermore, we show that extracellular Na+ profoundly alters the voltage-dependent E1P/E2P distribution indicating that Na+ ions can act as surrogates for protons regarding the E2P→E1P transition. The complexity of the intra- and extracellular cation effects can be rationalized by a kinetic model suggesting that cations reach the binding sites through a rather high-field intra- and a rather low-field extracellular access channel, with fractional electrical distances of ∼0.5 and ∼0.2, respectively

Preserving Charge and Oxidation State of Au(III) Ions in an Agent-Functionalized Nanocrystal Model System

Supporting functional molecules on crystal facets is an established technique in nanotechnology. To preserve the original activity of ionic metallorganic agents on a supporting template, conservation of the charge and oxidation state of, the active center is indispensable. We. present a model system of a metallorganic agent that, indeed, fulfills this design criterion on a technologically relevant metal support With potential Impact on Au(III)-porphyrin-functionalized nanoparticles for an improved anticancer-drug delivery. Employing scanning tunneling microscopy and -spectroscopy in combination with photoemission spectroscopy,we clarify at the single-molecule level the underlying mechanisms of this exceptional adsorption mode. It is based on the balance between a high-energy oxidation state and an electrostatic screening-response of the surface (image charge). Modeling with first principles methods reveals submolecular details of the metal-ligand bonding interaction and completes the study by providing an Illustrative electrostatic.. model relevant for ionic metalorganic agent molecules, in general

Effektivität eines Evidence-based Nursing Trainings im stationären Akutsetting der Urologie

Die Zunahme pflegewissenschaftlicher Studiengänge ermöglicht es immer mehr Pflegenden, sich zu akademisieren und Kompetenzen im wissenschaftlichen Arbeiten zu erlernen. Trotz der Zunahme an Studienangeboten in den letzten Jahren in Deutschland, stellt akademisiertes Pflegepersonal, welches in der direkten Patientenversorgung tätig ist, weiterhin eine Seltenheit dar. Dabei ist längst bekannt, dass Pflege nicht nur ineffizient, sondern auch gefährlich sein kann, beruht sie nicht auf aktueller Evidenz. Der Begriff des Evidence-based Nursings (EBN) gewinnt an immer größerer Bedeutung und muss Einzug in die Pflegepraxis finden. Das Forschungsprojekt untersucht die Effektivität eines EBN-Trainings unter Pflegenden einer urologischen Akutstation und ermittelt, wie sich die Einstellung und das Wissen der Teilnehmenden gegenüber EBN durch die Teilnahme am Training verändern. Bei dem Design handelt es sich um einen Mixed-Method-Ansatz. Dazu wurde ein skalierter Fragebogen aus zwei validierten Instrumenten zusammengefügt, mündliche Befragungen durchgeführt und Gedächtnisprotokolle genutzt. Im Rahmen einer Prätest-Posttest-Befragung wurde der aktuelle Wissensstand der Pflegenden sowie ihre Haltung gegenüber der Nutzung aktueller Forschungsergebnisse in der Pflegepraxis ermittelt. Zwischen den beiden Erhebungsphasen fand ein EBN-Training statt, welches sich in drei Sitzungen gliederte. Bei den Ergebnissen zeigten sich sowohl vor als auch nach der Durchführung des Trainings eine hohe Bereitschaft und Offenheit der Pflegenden, neue Forschungserkenntnisse in der Praxis zu nutzen. Die tatsächliche Umsetzung von Forschungserkenntnissen in der Praxis veränderte sich durch das EBN-Training nicht. Eine deutliche Zunahme konnte dagegen im Austausch der Pflegenden untereinander und der selbstständigen Recherche nach Literatur beobachtet werden. Auch äußerten alle Teilnehmenden nach dem Training, den Begriff EBN zu kennen oder zu verstehen. Nach der Teilnahme am EBN-Training gaben jedoch mehr Pflegende als zuvor an, durch ihre beruflichen Aufgaben keine Zeit für das Lesen wissenschaftlicher Literatur zu haben und wenig Unterstützung durch ihre Vorgesetzten zu erhalten. Durch diese Arbeit konnte gezeigt werden, dass im Team eine große Bereitschaft herrscht, die Praxis weiterzuentwickeln und neue Erkenntnisse in die praktische Arbeit einfließen zu lassen. Jedoch liegen auch viele Faktoren vor, welche die Implementierung einer evidenzbasierten Praxis behindern wie mangelnde zeitliche Ressourcen, fehlende Unterstützungsangebote und unzureichendes Wissen. Nachdem die Pflegenden zum ersten Mal mit dem EBN-Prozess in Berührung gekommen sind, herrscht auch nach dem Projekt noch eine gewisse Unsicherheit. Weitere Workshops und regelmäßige Treffen werden zukünftig nötig sein, um EBN langfristig in den Pflegealltag zu integrieren.The increase in nursing science courses of study enables more and more nurses to become academics and to learn competences in scientific work. Despite the increase in study programmes in Germany in recent years, academically trained nursing staff working in direct patient care is still a rarity. It has long been known that nursing care can be not only inefficient but also dangerous if it is not based on current evidence. The concept of evidence-based nursing (EBN) is becoming increasingly important and must find its way into nursing practice. The research project investigates the effectiveness of EBN training among nurses in an acute urology ward and determines how participants' attitudes and knowledge about EBN change as a result of participating in the training. The design was a mixed-method approach. For this purpose a scaled questionnaire from two validated instruments was combined, oral interviews were conducted and memory protocols were used. A pretest-posttest survey was conducted to de termine the current knowledge of nurses and their attitudes towards the use of current research findings in nursing practice. Between the two survey phases, EBN training took place, which was divided into three sessions. The results show a high willingness and openness among nurses to use new research findings in practice. The actual implementation of research findings in practice did not change as a result of the EBN training. On the other hand a clear increase could be observed in the exchange among the nurses and the independent research for literature. Also, none of the participants said after the training that they did not know or understand the term EBN. After participating in the EBN training, however, more nurses than before stated that they had no time for reading scientific literature due to their professional tasks and that they received little support from their superiors. Although there is a great willingness in the team to further develop the practice and to incorporate new findings into the practical work, there are many factors that hinder the implementation of evidence-based practice. After the nurses have been exposed to the EBN process for the first time, there is still some uncertainty after the project. Further workshops and regular meetings will be necessary in the future to integrate EBN into everyday car

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