Charakterisierung der Einflussfaktoren auf SERS-Spektren niedermolekularer Substanzen und medizinisch relevante Anwendungen des LOC-SERS-Systems

Die Kombination von oberflächenverstärkter Raman-Spektroskopie (SERS) und einem mikrofluidischen Lab-on-a-chip (LOC)-System ist ein vielversprechender analytischer Ansatz für die medizinische Diagnostik. Die SERS-Spektren enthalten molekularspezifische Informationen und ermöglichen somit eine Detektion molekularer Systeme im submikromolaren Bereich. Die LOC-SERS-Methode ermöglicht eine hohe Durchsatzrate von Einzelproben unter geringen Aufkommen von Probenvolumina. Weiterhin ist die Implementierung von Modulen zur Probenvorbehandlung mit geringem technischem Aufwand realisierbar. Im Rahmen dieser Arbeit sollen die vielfältigen Möglichkeiten des mikrofluidischen SERS-Systems aufgezeigt werden. Durch die Verwendung des LOC-SERS-Systems wird die Bestimmung exakter Messbedingungen und eine hohe Reproduzierbarkeit gewährleistet. In einer Grundlagenstudie werden in dieser Arbeit die Einflüsse auf SERS-Spektren untersucht. Hierbei werden Pyridin und monosubstituierte Pyridinderivate als Analyten verwendet. Es wird gezeigt, dass für eine akkurate Bandenzuordnung die Inklusion quantenchemischer Methoden unerlässlich ist. Es wird demonstriert, dass anhand von LOC-SERS-Datensätzen quantitative Analysen in komplexen Medien durchgeführt werden können. Der Antimetabolit Methotrexat (MTX) wird in wässriger Lösung sowie in artifiziellem Blutplasma semi-quantitativ detektiert, unterschiedliche Konzentrationen von MTX in realem Blutplasma können eindeutig unterschieden werden. Des Weiteren werden Pathogene mittels chemometrischer Methoden anhand der SERS-Spektren von Markermolekülen identifiziert. Im Fokus der Arbeit steht dabei die Detektion niedermolekularer Substanzen in komplexen Medien, wie Blutplasma und Bakteriensuspension sowie die Identifizierung pathogener Mykobakterien

Robots show us how to teach them: Feedback from robots shapes tutoring behavior during action learning

Vollmer A-L, Mühlig M, Steil JJ, et al. Robots show us how to teach them: Feedback from robots shapes tutoring behavior during action learning. PLoS ONE. 2014;9(3): e91349.Robot learning by imitation requires the detection of a tutor's action demonstration and its relevant parts. Current approaches implicitly assume a unidirectional transfer of knowledge from tutor to learner. The presented work challenges this predominant assumption based on an extensive user study with an autonomously interacting robot. We show that by providing feedback, a robot learner influences the human tutor's movement demonstrations in the process of action learning. We argue that the robot's feedback strongly shapes how tutors signal what is relevant to an action and thus advocate a paradigm shift in robot action learning research toward truly interactive systems learning in and benefiting from interaction

Coherent soft X-ray diffraction imaging of coliphage PR772 at the Linac coherent light source

Single-particle diffraction from X-ray Free Electron Lasers offers the potential for molecular structure determination without the need for crystallization. In an effort to further develop the technique, we present a dataset of coherent soft X-ray diffraction images of Coliphage PR772 virus, collected at the Atomic Molecular Optics (AMO) beamline with pnCCD detectors in the LAMP instrument at the Linac Coherent Light Source. The diameter of PR772 ranges from 65–70 nm, which is considerably smaller than the previously reported ~600 nm diameter Mimivirus. This reflects continued progress in XFEL-based single-particle imaging towards the single molecular imaging regime. The data set contains significantly more single particle hits than collected in previous experiments, enabling the development of improved statistical analysis, reconstruction algorithms, and quantitative metrics to determine resolution and self-consistency

Draft Genome Sequences of Three European Laboratory Derivatives from Enterohemorrhagic Escherichia coli O157:H7 Strain EDL933, Including Two Plasmids

Escherichia coliO157:H7 EDL933, isolated in 1982 in the United States, was the first enterohemorrhagicE. coli(EHEC) strain sequenced. Unfortunately, European labs can no longer receive the original strain. We checked three European EDL933 derivatives and found major genetic deviations (deletions, inversions) in two strains. All EDL933 strains contain the cryptic EHEC-plasmid, not reported before.publishe

VisExpress : Visual exploration of differential gene expression data

Biologists are keen to understand how processes in cells react to environmental changes. Differential gene expression analysis allows biologists to explore functions of genes with data generated from different environments. However, these data and analysis lead to unique challenges since tasks are ill-defined, require implicit domain knowledge, comprise large volumes of data, and are, therefore, of explanatory nature. To investigate a scalable visualization-based solution, we conducted a design study with three biologists specialized in differential gene expression analysis. We stress our contributions in three aspects: first, we characterize the problem domain for exploring differential gene expression data and derive task abstractions and design requirements. Second, we investigate the design space and present an interactive visualization system, called VisExpress. Third, we evaluate the usefulness of VisExpress via a Pair Analytics study with real users and real data and report on insights that were gained by our experts with VisExpress.publishe

Molecular Specific and Sensitive Detection of Pyrazinamide and Its Metabolite Pyrazinoic Acid by Means of Surface Enhanced Raman Spectroscopy Employing In Situ Prepared Colloids

The prodrug pyrazinamide (PZA) is metabolized by the mycobacteria to pyrazinoic acid (POA), which is expelled into the extracellular environment. PZA resistance is highly associated to a lack of POA efflux. Thus, by detecting a reduction of the concentration of POA in the extracellular environment, by means of lab-on-a-chip (LoC)-SERS (surface-enhanced Raman spectroscopy), an alternative approach for the discrimination of PZA resistant mycobacteria is introduced. A droplet-based microfluidic SERS device has been employed to illustrate the potential of the LoC-SERS method for the discrimination of PZA resistant mycobacteria. The two analytes were detected discretely in aqueous solution with a limit of detection of 27 µm for PZA and 21 µm for POA. The simultaneous detection of PZA and POA in aqueous mixtures could be realized within a concentration range from 20 μm to 50 μm for PZA and from 50 μm to 80 μm for POA

Rationalizing the binding modes of PET radiotracers targeting the norepinephrine transporter

A new PET radiotracer 18F-AF78 showing great potential for clinical application has been reported recently. It belongs to a new generation of phenethylguanidine-based norepinephrine transporter (NET)-targeting radiotracers. Although many efforts have been made to develop NET inhibitors as antidepressants, systemic investigations of the structure–activity relationships (SARs) of NET-targeting radiotracers have rarely been performed. Methods: Without changing the phenethylguanidine pharmacophore and 3-fluoropropyl moiety that is crucial for easy labeling, six new analogs of 18F-AF78 with different meta-substituents on the benzene-ring were synthesized and evaluated in a competitive cellular uptake assay and in in vivo animal experiments in rats. Computational modeling of these tracers was established to quantitatively rationalize the interaction between the radiotracers and NET. Results: Using non-radiolabeled reference compounds, a competitive cellular uptake assay showed a decrease in NET-transporting affinity from meta-fluorine to iodine (0.42 and 6.51 µM, respectively), with meta-OH being the least active (22.67 µM). Furthermore, in vivo animal studies with radioisotopes showed that heart-to-blood ratios agreed with the cellular experiments, with AF78(F) exhibiting the highest cardiac uptake. This result correlates positively with the electronegativity rather than the atomic radius of the meta-substituent. Computational modeling studies revealed a crucial influence of halogen substituents on the radiotracer–NET interaction, whereby a T-shaped π–π stacking interaction between the benzene-ring of the tracer and the amino acid residues surrounding the NET binding site made major contributions to the different affinities, in accordance with the pharmacological data. Conclusion: The SARs were characterized by in vitro and in vivo evaluation, and computational modeling quantitatively rationalized the interaction between radiotracers and the NET binding site. These findings pave the way for further evaluation in different species and underline the potential of AF78(F) for clinical application, e.g., cardiac innervation imaging or molecular imaging of neuroendocrine tumors

Action learning concept graphics.

<p>(A) Unidirectional concept of current imitation learning approaches: The tutor demonstrates the action (white oval) according to his/her knowledge (upper hatched oval). The learner passively observes the action demonstration and learns the action. (B) Interactionist concept of learning: The tutor demonstrates the action (upper white oval) corresponding to his/her knowledge (upper hatched oval) emphasizing what is relevant to the action accordingly. The learner's level of understanding or knowledge of the action (lower hatched oval) is communicated by his/her feedback (lower white oval). This feedback directly influences the tutor's action demonstration. The tutor monitors the learner's feedback, builds hypotheses about the learner's understanding, and reacts by changing his/her demonstration accordingly as will be shown in this contribution.</p