Imaging and Positioning of Objects at the Nanoscale

The process of miniaturization brings benefits in many areas of every day life. It describes the process of down-scaling mechanical, optical and electronic devices while maintaining their function. This continuous process has brought up the field of nanotechnology. It allows computers to run faster and faster while reducing their size and energy consumption. Many bio-analytical applications profit from smaller sizes to be more sensitive with lower sample volumes. Finally, each and every living cell contains the most complex nanoscopic machinery. In order to mimic nature’s highly efficient concepts, they first of all need to be understood. Their nanoscopic dimensions, however, make this task a very challenging one. Direct observation of subcellular processes by conventional light microscopy is difficult as almost all cellular components are colorless. Fluorescence microscopy introduces sufficient contrast and can be specifically applied to many different target molecules but remains limited in its spatial resolution. In this work, a new approach to increase the resolution of fluorescence microscopy is presented that is termed “blink microscopy”. It is based on the subsequent localization of single molecules as it is realized in recent techniques known as STORM or PALM, but does not require special photoswitchable fluorophores or multiple lasers. Instead of photoswitching, reversible electron transfer reactions are used to generate the required dark states. Motivated by the task to assess the resolution of blink microscopy, DNA nanotechnology is used for nano-construction of a calibration structure. The DNA origami technique, developed by Paul Rothemund in 2006, allows for arranging of individual fluorophores at distances of 1–100 nm on a DNA nanostructure. While it is impossible to resolve two spots at a distance below 200 nm with conventional fluorescence microscopy, it was possible to confidently resolve 50 nm with blink microscopy. These experiments prove both, blink microscopy to be able to reliably resolve small distances and DNA origami structures to be well suited as a rigid breadboard for fluorescence experiments. This research pioneering the combination of the two powerful tools of nano-imaging and nanoconstruction set the ground for further experiments. After the rigidity of DNA origami structures was used to characterize a fluorescence technique, single-molecule fluorescence could also help to characterize properties of the DNA origami. Namely, dynamic processes on a DNA nanostructure were exemplarily studied by reversible binding of a fluorescently labeled DNA strand while observing this process in real-time on a fluorescence microscope. With the knowledge about binding and unbinding kinetics of DNA and imaging of single molecules, another super-resolution approach was developed that is simply and flexibly implemented in DNA structures, not limited by photobleaching, easy to extend to multiple colors and that shows potential for cellular imaging

[P4H]+[Al(OTeF5)4]−: protonation of white phosphorus with the Brønsted superacid H[Al(OTeF5)4](solv)

A sustainable transformation of white phosphorus (P4) into chemicals of higher value is one of the key aspects in modern phosphorus research. Even though the chemistry of P4 has been investigated for many decades, its chemical reactivity towards the simplest electrophile, the proton, is still virtually unknown. Based on quantum-chemical predictions, we report for the first time the successful protonation of P4 by the Brønsted acid H[Al(OTeF5)4](solv). Our spectroscopic results are in agreement with acid-mediated activation of P4 under protonation of an edge of the P4-tetrahedron and formation of a three-center two-electron P–H–P bond. These investigations are of fundamental interest as they permit the activation of P4 with the simplest electrophile as a new prototype reaction for this molecule

Inhibition of Acinetobacter baumannii, Staphylococcus aureus and Pseudomonas aeruginosa biofilm formation with a class of TAGE-triazole conjugates

This is the published version. Copyright Royal Society of ChemistryA chemically diverse library of TAGE-triazole conjugates was synthesized utilizing click chemistry on the TAGE scaffold. This library of small molecules was screened for anti-biofilm activity and found to possess the ability of inhibiting biofilm formation against Acinetobacter baumannii, Staphylococcus aureus and Pseudomonas aeruginosa. One such compound in this library demonstrated the most potent inhibitory effect against Staphylococcus aureus biofilm formation that has been displayed by any 2-aminoimidazole derivative

Synthesis, Crystallographic Characterization and Reactivity of a Phosphinine-B(C6F5)3 Lewis Pair

A phosphinine-borane adduct of a Me3Si-functionalized phosphinine and the Lewis acid B(C6F5)3 has been synthesized and characterized crystallographically for the first time. The reaction strongly depends on the nature of the substituents in the α-position of the phosphorus heterocycle. In contrast, the reaction of B2H6 with various substituted phosphinines leads to an equilibrium between the starting materials and the phosphinine–borane adducts that is determined by the Lewis basicity of the phosphinine. The novel phosphinine borane adduct (6-B(C6F5)3) shows rapid and facile insertion and [4+2] cycloaddition reactivity towards phenylacetylene. A hitherto unknown dihydro-1-phosphabarrelene is formed with styrene. The reaction with an ester provides a new, facile and selective route to 1-R-phosphininium salts. These salts then undergo a [4+2] cycloaddition in the presence of Me3Si−C≡CH and styrene to cleanly form unprecedented derivatives of 1-R-phosphabarrelenium salts

Mechanisms and advancement of antifading agents for fluorescence microscopy and single-molecule spectroscopy

Modern fluorescence microscopy applications go along with increasing demands for the employed fluorescent dyes. In this work, we compared antifading formulae utilizing a recently developed reducing and oxidizing system (ROXS) with commercial antifading agents. To systematically test fluorophore performance in fluorescence imaging of biological samples, we carried out photobleaching experiments using fixed cells labeled with various commonly used organic dyes, such as Alexa 488, Alexa 594, Alexa 647, Cy3B, ATTO 550, and ATTO 647N. Quantitative evaluation of (i) photostability, (ii) brightness, and (iii) storage stability of fluorophores in samples mounted in different antifades (AFs) reveal optimal combinations of dyes and AFs. Based on these results we provide guidance on which AF should preferably be used with a specific dye. Finally, we studied the antifading mechanisms of the commercial AFs using single-molecule spectroscopy and reveal that these empirically selected AFs exhibit similar properties to ROXS AFs

Surface Chemistry of the Molecular Solar Thermal Energy Storage System 2,3-Dicyano-Norbornadiene/Quadricyclane on Ni(111)

Molecular solar thermal (MOST) systems are a promising approach for the introduction of sustainable energy storage solutions. We investigated the feasibility of the dicyano-substituted norbornadiene/quadricyclane molecule pair on Ni(111) for catalytic model studies. This derivatization is known to lead to a desired bathochromic shift of the absorption maximum of the parent compound. In our experiments further favorable properties were found: At low temperatures, both molecules adsorb intact without any dissociation. In situ temperature-programmed HR-XPS experiments reveal the conversion of (CN)2-quadricyclane to (CN)2-norbornadiene under energy release between 175 and 260 K. The absence of other surface species due to side reactions indicates full isomerization. Further heating leads to the decomposition of the molecular framework into smaller carbonaceous fragments above 290 K and finally to amorphous structures, carbide and nitride above 400 K. DFT calculations gave insights into the adsorption geometries. (CN)2-norbornadiene is expected to interact stronger with the surface, with flat configurations being favorable. (CN)2-quadricyclane exhibits smaller adsorption energies with negligible differences for flat and side-on geometries. Simulated XP spectra are in good agreement with experimental findings further supporting the specific spectroscopic fingerprints for both valence isomers

Surface Studies on the Energy Release of the MOST System 2-Carbethoxy-3-Phenyl-Norbornadiene/Quadricyclane (PENBD/PEQC) on Pt(111) and Ni(111)

Novel energy-storage solutions are necessary for the transition from fossil to renewable energy sources. Auspicious candidates are so-called molecular solar thermal (MOST) systems. In our study, we investigate the surface chemistry of a derivatized norbornadiene/quadricyclane molecule pair. By using suitable push–pull substituents, a bathochromic shift of the absorption onset is achieved, allowing a greater overlap with the solar spectrum. Specifically, the adsorption and thermally induced reactions of 2-carbethoxy-3-phenyl-norbornadiene/quadricyclane are assessed on Pt(111) and Ni(111) as model catalyst surfaces by synchrotron radiation-based X-ray photoelectron spectroscopy (XPS). Comparison of the respective XP spectra enables the distinction of the energy-rich molecule from its energy-lean counterpart and allows qualitative information on the adsorption motifs to be derived. Monitoring the quantitative cycloreversion between 140 and 230 K spectroscopically demonstrates the release of the stored energy to be successfully triggered on Pt(111). Heating to above 300 K leads to fragmentation of the molecular framework. On Ni(111), no conversion of the energy-rich compound takes place. The individual decomposition pathways of the two isomers begin at 160 and 180 K, respectively. Pronounced desorption of almost the entire surface coverage only occurs for the energy-lean molecule on Ni(111) above 280 K; this suggests weakly bound species. The correlation between adsorption motif and desorption behavior is important for applications of MOST systems in heterogeneously catalyzed processes

Super-Resolution Imaging of C-Type Lectin and Influenza Hemagglutinin Nanodomains on Plasma Membranes Using Blink Microscopy

AbstractDendritic cells express DC-SIGN, a C-type lectin (CTL) that binds a variety of pathogens and facilitates their uptake for subsequent antigen presentation. DC-SIGN forms remarkably stable microdomains on the plasma membrane. However, inner leaflet lipid markers are able to diffuse through these microdomains suggesting that, rather than being densely packed with DC-SIGN proteins, an elemental substructure exists. Therefore, a super-resolution imaging technique, Blink Microscopy (Blink), was applied to further investigate the lateral distribution of DC-SIGN. Blink indicates that DC-SIGN, another CTL (CD206), and influenza hemagglutinin (HA) are all localized in small (∼80 nm in diameter) nanodomains. DC-SIGN and CD206 nanodomains are randomly distributed on the plasma membrane, whereas HA nanodomains cluster on length scales up to several microns. We estimate, as a lower limit, that DC-SIGN and HA nanodomains contain on average two tetramers or two trimers, respectively, whereas CD206 is often nonoligomerized. Two-color Blink determined that different CTLs rarely occupy the same nanodomain, although they appear colocalized using wide-field microscopy. What to our knowledge is a novel domain structure emerges in which elemental nanodomains, potentially capable of binding viruses, are organized in a random fashion; evidently, these nanodomains can be clustered into larger microdomains that act as receptor platforms for larger pathogens like yeasts

Podiumsdiskussion: "Auf dem Weg zu einem Bibliotheksgesetz"

Teilnehmer: - André Blechschmidt MdL, Sprecher für Justiz, Medien und Sport der Landtagsfraktion Die Linke. PDS - Hans-Jürgen Döring MdL, Sprecher für Bildung und Kultur der SPD-Landtagsfraktion - Christian Hasiewicz, Bertelsmann Stiftung - Barbara Schleihagen, Leiterin der Geschäftsstelle des DBV e.V. - Jörg Schwäblein MdL, Sprecher des Arbeitskreises Wissenschaft, Kunst und Medien der CDU-Landtagsfraktion - Eric W. Steinhauer, Universitätsbibliothek Ilmenau/VDB-Regionalvorsitzender Moderation: Dr. Frank Simon-Ritz, Direktor der Universitätsbibliothek der Bauhaus Universität Weima