Sedimentation of large, soluble proteins up to 140 kDa for 1H-detected MAS NMR and 13C DNP NMR - practical aspects

Solution NMR is typically applied to biological systems with molecular weights < 40 kDa whereas magic-angle-spinning (MAS) solid-state NMR traditionally targets very large, oligomeric proteins and complexes exceeding 500 kDa in mass, including fibrils and crystalline protein preparations. Here, we propose that the gap between these size regimes can be filled by the approach presented that enables investigation of large, soluble and fully protonated proteins in the range of 40-140 kDa. As a key step, ultracentrifugation produces a highly concentrated, gel-like state, resembling a dense phase in spontaneous liquid-liquid phase separation (LLPS). By means of three examples, a Sulfolobus acidocaldarius bifurcating electron transfer flavoprotein (SulfETF), tryptophan synthases from Salmonella typhimurium (StTS) and the dimeric β-subunits from Pyrococcus furiosus (PfTrpB), we show that such samples yield well-resolved proton-detected 2D and 3D NMR spectra at 100 kHz MAS without heterogeneous broadening, similar to diluted liquids. Herein, we provide practical guidance on centrifugation conditions and tools, sample behavior, and line widths expected. We demonstrate that the observed chemical shifts correspond to those obtained from μM/low mM solutions or crystalline samples, indicating structural integrity. Nitrogen line widths as low as 20-30 Hz are observed. The presented approach is advantageous for proteins or nucleic acids that cannot be deuterated due to the expression system used, or where relevant protons cannot be re-incorporated after expression in deuterated medium, and it circumvents crystallization. Importantly, it allows the use of low-glycerol buffers in dynamic nuclear polarization (DNP) NMR of proteins as demonstrated with the cyanobacterial phytochrome Cph1.

Indole Diketopiperazine Alkaloids from the Marine Sediment-Derived Fungus Aspergillus chevalieri against Pancreatic Ductal Adenocarcinoma

A new prenylated indole diketopiperazine alkaloid, rubrumline P (1), was isolated along with six more analogues and characterized from the fermentation culture of a marine sediment-derived fungus, Aspergillus chevalieri, collected at a depth of 15 m near the lighthouse in Dahab, Red Sea, Egypt. In the current study, a bioassay-guided fractionation allowed for the identification of an active fraction displaying significant cytotoxic activity against the human pancreatic adenocarcinoma cell line PANC-1 from the EtOAc extract of the investigated fungus compared to the standard paclitaxel. The structures of the isolated compounds from the active fraction were established using 1D/2D NMR spectroscopy and mass spectrometry, together with comparisons with the literature. The absolute configuration of the obtained indole diketopiperazines was established based on single-crystal X-ray diffraction analyses of rubrumline I (2) and comparisons of optical rotations and NMR data, as well as on biogenetic considerations. Genome sequencing indicated the formation of prenyltransferases, which was subsequently confirmed by the isolation of mono-, di-, tri-, and tetraprenylated compounds. Compounds rubrumline P (1) and neoechinulin D (4) confirmed preferential cytotoxic activity against PANC-1 cancer cells with IC50 values of 25.8 and 23.4 µM, respectively. Although the underlying mechanism-of-action remains elusive in this study, cell cycle analysis indicated a slight increase in the sub-G1 peak after treatment with compounds 1 and 4.

Osmotically Delaminated Silicate Nanosheet-Coated NCM for Ultra-Stable Li+ Storage and Chemical Stability Toward Long-Term Air Exposure

To ensure the safety and performance of lithium-ion batteries (LIBs), a rational design and optimization of suitable cathode materials are crucial. Lithium nickel cobalt manganese oxides (NCM) represent one of the most popular cathode materials for commercial LIBs. However, they are limited by several critical issues, such as transition metal dissolution, formation of an unstable cathode-electrolyte interphase (CEI) layer, chemical instability upon air exposure, and mechanical instability. In this work, coating fabricated by self-assembly of osmotically delaminated sodium fluorohectorite (Hec) nanosheets onto NCM (Hec-NCM) in a simple and technically benign aqueous wet-coating process is reported first. Complete wrapping of NCM by high aspect ratio (>10 000) nanosheets is enabled through an electrostatic attraction between Hec nanosheets and NCM as well as by the superior mechanical flexibility of Hec nanosheets. The coating significantly suppresses mechanical degradation while forming a multi-functional CEI layer. Consequently, Hec-NCM delivers outstanding capacity retention for 300 cycles. Furthermore, due to the exceptional gas barrier properties of the few-layer Hec-coating, the electrochemical performance of Hec-NCM is maintained even after 6 months of exposure to the ambient atmosphere. These findings suggest a new direction of significantly improving the long-term stability and activity of cathode materials by creating an artificial CEI layer.

Reducing energy system model distortions from unintended storage cycling through variable costs

Energy system models are used for policy decisions and technology designs. If not carefully used, models give implausible outputs and mislead decision-making. One implausible effect is "unintended storage cycling", which is observable as simultaneous storage charging and discharging. Methods to remove such misleading effects exist, but are computationally inefficient and sometimes ineffective. Through 124 simulations, we find that determining appropriate levels of variable costs depends on the variable cost allocation to certain components and the solver accuracy used for the optimization. For the latter, if the accuracy is set too loosely, the solver prevents the removal of unintended storage cycling. We further provide a list of recommended variable cost model inputs as well as a minimum threshold that can significantly reduce the magnitude and likeliness of unintended storage cycling. Finally, our results suggest that our approach can remove other similar misleading effects such as unintended line cycling or sector cycling.

AInSn2S6 (A = K, Rb, Cs)─Layered Semiconductors Based on the SnS2 Structure

RbInSn₂S₆ and CsInSn₂S₆ are yellow two-dimensional (2D) semiconductors featuring anionic SnS₂-type layers of edge-sharing (In/Sn)S₆ octahedra. These structures are directly derived from the parent structure of SnS₂ by replacement of Sn⁴⁺ atoms with A⁺ and In³⁺ atoms. The compounds crystallize, isotypic to the ion-exchange material KInSn₂S₆. They adopt the triclinic space group R3̅m (no. 166). The compounds have similar indirect optical band gaps of 2.31(5) eV for Rb and 2.47(5) eV Cs. The measured work functions for each material are ∼5.38 eV. The density functional theory-calculated effective mass values exhibit strong anisotropy due to the 2D nature of the crystal structures and in the case of CsInSn₂S₆ for hole carriers along the a, b, and c crystallographic directions are 0.30 m₀, 0.34 m₀, and 2.54 m₀, respectively, while for electrons are 0.06 m₀, 0.07 m₀, and 0.47 m₀, respectively.

The metaphorical swiss army knife: The multitude and diverse roles of HEAT domains in eukaryotic translation initiation

Biomolecular associations forged by specific interaction among structural scaffolds are fundamental to the control and regulation of cell processes. One such structural architecture, characterized by HEAT repeats, is involved in a multitude of cellular processes, including intracellular transport, signaling, and protein synthesis. Here, we review the multitude and versatility of HEAT domains in the regulation of mRNA translation initiation. Structural and cellular biology approaches, as well as several biophysical studies, have revealed that a number of HEAT domain-mediated interactions with a host of protein factors and RNAs coordinate translation initiation. We describe the basic structural architecture of HEAT domains and briefly introduce examples of the cellular processes they dictate, including nuclear transport by importin and RNA degradation. We then focus on proteins in the translation initiation system featuring HEAT domains, specifically the HEAT domains of eIF4G, DAP5, eIF5, and eIF2Bϵ. Comparative analysis of their remarkably versatile interactions, including protein–protein and protein–RNA recognition, reveal the functional importance of flexible regions within these HEAT domains. Here we outline how HEAT domains orchestrate fundamental aspects of translation initiation and highlight open mechanistic questions in the area.

Thick-Layer Lead Iodide Perovskites with Bifunctional Organic Spacers Allylammonium and Iodopropylammonium Exhibiting Trap-State Emission

The nature of the organic cation in two-dimensional (2D) hybrid lead iodide perovskites tailors the structural and technological features of the resultant material. Herein, we present three new homologous series of (100) lead iodide perovskites with the organic cations allylammonium (AA) containing an unsaturated C═C group and iodopropylammonium (IdPA) containing iodine on the organic chain: (AA)₂MA_n-1Pb_nI_3n+1 (n = 3-4), [(AA)_x(IdPA)_1-x]₂MA_n-1Pb_nI_3n+1 (n = 1-4), and (IdPA)₂MA_n-1Pb_nI_3n+1 (n = 1-4), as well as their perovskite-related substructures. We report the in situ transformation of AA organic layers into IdPA and the incorporation of these cations simultaneously into the 2D perovskite structure. Single-crystal X-ray diffraction shows that (AA)₂MA₂Pb₃I₁₀ crystallizes in the space group P2₁/c with a unique inorganic layer offset (0, <1/2), comprising the first example of n = 3 halide perovskite with a monoammonium cation that deviates from the Ruddlesden-Popper (RP) halide structure type. (IdPA)₂MA₂Pb₃I₁₀ and the alloyed [(AA)_x(IdPA)_1-x]₂MA₂Pb₃I₁₀ crystallize in the RP structure, both in space group P2₁/c. The adjacent I···I interlayer distance in (AA)₂MA₂Pb₃I₁₀ is ∼5.6 Å, drawing the [Pb₃I₁₀]^4- layers closer together among all reported n = 3 RP lead iodides. (AA)₂MA₂Pb₃I₁₀ presents band-edge absorption and photoluminescence (PL) emission at around 2.0 eV that is slightly red-shifted in comparison to (IdPA)₂MA₂Pb₃I₁₀. The band structure calculations suggest that both (AA)₂MA₂Pb₃I₁₀ and (IdPA)₂MA₂Pb₃I₁₀ have in-plane effective masses around 0.04m₀ and 0.08m₀, respectively. IdPA cations have a greater dielectric contribution than AA. The excited-state dynamics investigated by transient absorption (TA) spectroscopy reveal a long-lived (∼100 ps) trap state ensemble with broad-band emission; our evidence suggests that these states appear due to lattice distortions induced by the incorporation of IdPA cations.

Performance-Based Screening of Porous Materials for Carbon Capture

Computational screening methods have changed the way new materials and processes are discovered and designed. For adsorption-based gas separations and carbon capture, recent efforts have been directed toward the development of multiscale and performance-based screening workflows where we can go from the atomistic structure of an adsorbent to its equilibrium and transport properties at different scales, and eventually to its separation performance at the process level. The objective of this work is to review the current status of this new approach, discuss its potential and impact on the field of materials screening, and highlight the challenges that limit its application. We compile and introduce all the elements required for the development, implementation, and operation of multiscale workflows, hence providing a useful practical guide and a comprehensive source of reference to the scientific communities who work in this area. Our review includes information about available materials databases, state-of-the-art molecular simulation and process modeling tools, and a complete catalogue of data and parameters that are required at each stage of the multiscale screening. We thoroughly discuss the challenges associated with data availability, consistency of the models, and reproducibility of the data and, finally, propose new directions for the future of the field.

Comparative analysis of sustainability measures in the apparel industry: An empirical consumer and market study in Germany

The pressure on the apparel industry to make its products more sustainable is growing. Concrete measures have hardly been taken so far, also because they aim to avoid consumption which reduces profits. Studies mostly examine impacts on the environment, but not how the market volume can remain at a maximum for producers. To uncover direct market effects from sustainability approaches, this study asked 500 German consumers about their willingness-to-pay and preference order for three different measures, namely "slowing in consumption", "recyclability of petrochemical clothing" or its "production from bioplastics". An outdoor trekking jacket served as test object, and influences from sociodemographic and latent variables, as sportiness and environmental awareness, were measured. The results were mapped in a market model from which the output volume was derived. It was found that interest in the topic of plastics-containing outdoor clothing was rather determined by the application. This increased with the sportiness of the respondents (r = 0.13; p = 0.003), but not with their personal environmental awareness. Consent to bioplastics use did not depend on the level of experience, but older consumers appreciated this option more (p = 0.027). Only 20% of the respondents favoured slowing, 26% bioplastics, but 53% recycling of petroplastics. Therefore, research should investigate recyclability, policy should support this measure, and companies should practice take-back and reuse in new clothing. Consumers can maintain fast consumption and would even accept higher prices.

MAS NMR detection of hydrogen bonds for protein secondary structure characterization

Hydrogen bonds are essential for protein structure and function, making experimental access to long-range interactions between amide protons and heteroatoms invaluable. Here we show that measuring distance restraints involving backbone hydrogen atoms and carbonyl- or α-carbons enables the identification of secondary structure elements based on hydrogen bonds, provides long-range contacts and validates spectral assignments. To this end, we apply specifically tailored, proton-detected 3D (H)NCOH and (H)NCAH experiments under fast magic angle spinning (MAS) conditions to microcrystalline samples of SH3 and GB1. We observe through-space, semi-quantitative correlations between protein backbone carbon atoms and multiple amide protons, enabling us to determine hydrogen bonding patterns and thus to identify β-sheet topologies and α-helices in proteins. Our approach shows the value of fast MAS and suggests new routes in probing both secondary structure and the role of functionally-relevant protons in all targets of solid-state MAS NMR.

pH-Dependent Protonation of Surface Carboxylate Groups in PsbO Enables Local Buffering and Triggers Structural Changes

Photosystem II (PSII) catalyzes the splitting of water, releasing protons and dioxygen. Its highly conserved subunit PsbO extends from the oxygen‐evolving center (OEC) into the thylakoid lumen and stabilizes the catalytic Mn₄CaO₅ cluster. The high degree of conservation of accessible negatively charged surface residues in PsbO suggests additional functions, as local pH buffer or by affecting the flow of protons. For this discussion, we provide an experimental basis, through the determination of pK_a values of water‐accessible aspartate and glutamate side‐chain carboxylate groups by means of NMR. Their distribution is strikingly uneven, with high pK_a values around 4.9 clustered on the luminal PsbO side and values below 3.5 on the side facing PSII. pH‐dependent changes in backbone chemical shifts in the area of the lumen‐exposed loops are observed, indicating conformational changes. In conclusion, we present a site‐specific analysis of carboxylate group proton affinities in PsbO, providing a basis for further understanding of proton transport in photosynthesis.

Collective exchange processes reveal an active site proton cage in bacteriorhodopsin

Proton translocation across membranes is vital to all kingdoms of life. Mechanistically, it relies on characteristic proton flows and modifications of hydrogen bonding patterns, termed protonation dynamics, which can be directly observed by fast magic angle spinning (MAS) NMR. Here, we demonstrate that reversible proton displacement in the active site of bacteriorhodopsin already takes place in its equilibrated dark-state, providing new information on the underlying hydrogen exchange processes. In particular, MAS NMR reveals proton exchange at D85 and the retinal Schiff base, suggesting a tautomeric equilibrium and thus partial ionization of D85. We provide evidence for a proton cage and detect a preformed proton path between D85 and the proton shuttle R82. The protons at D96 and D85 exchange with water, in line with ab initio molecular dynamics simulations. We propose that retinal isomerization makes the observed proton exchange processes irreversible and delivers a proton towards the extracellular release site.

Daniel Friedrich et al. show that reversible proton translocation occurs in the dark–state of bacteriorhodopsin, involving the retinal Schiff base and D85 exchanging protons with H₂O. They find evidence of an active site proton cage and possible proton transfer via R82.

Space- and time-resolved UV-to-NIR surface spectroscopy and 2D nanoscopy at 1 MHz repetition rate

We describe a setup for time-resolved photoemission electron microscopy with aberration correction enabling 3 nm spatial resolution and sub-20 fs temporal resolution. The latter is realized by our development of a widely tunable (215-970 nm) noncollinear optical parametric amplifier (NOPA) at 1 MHz repetition rate. We discuss several exemplary applications. Efficient photoemission from plasmonic Au nanoresonators is investigated with phase-coherent pulse pairs from an actively stabilized interferometer. More complex excitation fields are created with a liquid-crystal-based pulse shaper enabling amplitude and phase shaping of NOPA pulses with spectral components from 600 to 800 nm. With this system we demonstrate spectroscopy within a single plasmonic nanoslit resonator by spectral amplitude shaping and investigate the local field dynamics with coherent two-dimensional (2D) spectroscopy at the nanometer length scale ("2D nanoscopy"). We show that the local response varies across a distance as small as 33 nm in our sample. Further, we report two-color pump-probe experiments using two independent NOPA beamlines. We extract local variations of the excited-state dynamics of a monolayered 2D material (WSe₂) that we correlate with low-energy electron microscopy (LEEM) and reflectivity measurements. Finally, we demonstrate the in situ sample preparation capabilities for organic thin films and their characterization via spatially resolved electron diffraction and dark-field LEEM.

Spatial Variations in Femtosecond Field Dynamics within a Plasmonic Nanoresonator Mode

Plasmonic resonators can be designed to support spectrally well-separated discrete modes. The associated characteristic spatial patterns of intense electromagnetic hot-spots can be exploited to enhance light-matter interaction. Here, we study the local field dynamics of individual hot-spots within a nanoslit resonator by detecting characteristic changes of the photoelectron emission signal on a scale of ∼12 nm using time-resolved photoemission electron microscopy (TR-PEEM) and by excitation with the output from a 20 fs, 1 MHz noncollinear optical parametric amplifier (NOPA). Surprisingly, we detect apparent spatial variations of the Q-factor and resonance frequency that are commonly considered to be global properties for a single mode. By using the concept of quasinormal modes we explain these local differences by crosstalk of adjacent resonator modes. Our findings are important in view of time-domain studies of plasmon-mediated strong light-matter coupling at ambient conditions.

Nonclassical Optical Properties of Mesoscopic Gold

Gold nanostructures have important applications in nanoelectronics, nano-optics, and in precision metrology due to their intriguing optoelectronic properties. These properties are governed by the bulk band structure but to some extent are tunable via geometrical resonances. Here we show that the band structure of gold itself exhibits significant size-dependent changes already for mesoscopic critical dimensions below 30 nm. To suppress the effects of geometrical resonances and grain boundaries, we prepared atomically flat ultrathin films of various thicknesses by utilizing large chemically grown single-crystalline gold platelets. We experimentally probe thickness-dependent changes of the band structure by means of two-photon photoluminescence and observe a surprising 100-fold increase of the nonlinear signal when the gold film thickness is reduced below 30 nm allowing us to optically resolve single-unit-cell steps. The effect is well explained by density functional calculations of the thickness-dependent 2D band structure of gold.

Time-resolved photoemission electron microscopy of a plasmonic slit resonator using 1 MHz, 25 fs, UV-to-NIR-tunable pulses

We discriminate different field dynamics across distances as small as 33 nm within a plasmonic slit resonator using aberration-corrected photoemission electron microscopy and a tunable broadband optical parametric amplifier at 1 MHz repetition rate.

[The ulm emergency algorithm for the acute treatment of drug-induced, bradykinin-mediated angioedema]

BACKGROUND

Bradykinin-mediated, drug-induced edema like ACE-inhibitor-induced angioedema (ACEi AE) is almost exclusively located in the head and neck region and is potentially life threatening. To date, there are no guidelines or officially-approved treatments available for this pathology.

OBJECTIVES

We sought to provide a structured therapeutic algorithm for the acute treatment of drug-induced bradykinin-mediated angioedema.

MATERIALS AND METHODS

We analyzed data (especially the course of disease and therapy) of all patients with acute angioedema, who presented to the Department of Otorhinolaryngology, Head and Neck Surgery at the University of Ulm (2010-2015). We also conducted a literature review on PubMed with the terms "acute angioedema", "angioedema emergency", "ACE angioedema", "bradykinin angioedema" and "angioedema therapy". Other fundamental references were the recent German guidelines "hereditary angioedema", "anaphylaxis" and "airway management".

RESULTS

An emergency algorithm was generated as a flowchart for the acute therapy of bradykinin-mediated drug-induced angioedema was generated. We focused on the decision criteria for intubation/airway management and pharmacological therapy: antihistamines and glucocorticoids versus anti-bradykinin treatment. Furthermore, recommendations for inpatient monitoring have been derived.

CONCLUSION/DISCUSSION

To date, therapy of drug-induced bradykinin-mediated angioedema is performed according to an "off-label" use and without officially-approved guidelines. The presented emergency algorithm provides a first approach for a structured therapeutic concept for a potentially life-threatening pathology.

In Situ X-ray Diffraction Study of the Thermal Decomposition of Selenogallates Cs2[Ga2(Se2)2- xSe2+ x] ( x = 0, 1, 2)

The selenogallates CsGaSe₃ and Cs₂Ga₂Se₅ release gaseous selenium upon heating. An in situ high-temperature X-ray powder diffraction analysis revealed a two-step degradation process from CsGaSe₃ to Cs₂Ga₂Se₅ and finally to CsGaSe₂. During each step, one Se₂^2- unit of the anionic chains in Cs₂[Ga₂(Se₂)_{2- x}Se_{2+ x}] ( x = 0, 1, 2) decomposes, and one equivalent of selenium is released. This thermal decomposition can be reverted by simple addition of elemental selenium and subsequent annealing of the samples below the decomposition temperature. The influence of the diselenide units in the anionic selenogallate chains on the optical properties and electronic structures was further studied by UV/vis diffuse reflectance spectroscopy and relativistic density functional theory calculations, revealing increasing optical band gaps with decreasing Se₂^2- content.

Virtuelle Planung bei der epithetischen Orbitaversorgung

Die optimale epithetische Versorgung von Patienten mit orbitalen Defekten stellt eine Herausforderung dar. Sowohl das Wählen des Implantations-Winkels als auch die Positionierung der Einzelimplantate kann bei inkorrekter Ausführung bei der Abformung, der Herstellung und dem Tragen der Epithese zu Problemen führen.

Wir führten eine virtuelle Planung der enossalen Implantation an einem 3D-CT-Datensatz mit der Software CoDiagnostiX ™(DentalWings, Montréal, Kanada) durch. Mittels 3D-Druckverfahren erfolgte die Herstellung einer plastischen-Insertionsschablone (Med-610™, Stratasys, Rehovot, Israel).

Bei einem 41-jährigen Patienten wurde bei Schrumpfung des Lidapparates nach Enukleation und Radiatio der linken Orbita vor 20 Jahren, nun eine Exenteratio orbitae durchgeführt. Im Anschluss erfolgte das Einbringen von 4 Vistafix-3 Implantaten (Cochlear™ Centennial, USA) mittels 3D-Schablone. Die Abformung und Epithesenanpassung im Verlauf war problemlos möglich und ergab eine sehr gute funktionelle und ästhetische Rehabilitation des Patienten.

Die virtuelle 3D-Planung der knochenverankerten epithetischen Versorgung von Orbitadefekten ist gut durchführbar und führt zu einer optimalen Platzierung der Implantate insbesondere bei posttherapeutisch veränderten anatomischen Verhältnissen der Orbitaregion.

Polymorphism of CsGaS2– structural characterization of a new two-dimensional polymorph and study of the phase-transition kinetics

Anionic layers in CsGaS₂undergo a transition to infinite strands at high temperature and transfer back under pressure.

Regulatory T cell frequencies are increased in preterm infants with clinical early-onset sepsis

The predisposition of preterm neonates to invasive infection is, as yet, incompletely understood. Regulatory T cells (Tregs ) are potential candidates for the ontogenetic control of immune activation and tissue damage in preterm infants. It was the aim of our study to characterize lymphocyte subsets and in particular CD4(+) CD25(+) forkhead box protein 3 (FoxP3)(+) Tregs in peripheral blood of well-phenotyped preterm infants (n = 117; 23 + 0 - 36 + 6 weeks of gestational age) in the first 3 days of life in comparison to term infants and adults. We demonstrated a negative correlation of Treg frequencies and gestational age. Tregs were increased in blood samples of preterm infants compared to term infants and adults. Notably, we found an increased Treg frequency in preterm infants with clinical early-onset sepsis while cause of preterm delivery, e.g. chorioamnionitis, did not affect Treg frequencies. Our data suggest that Tregs apparently play an important role in maintaining maternal-fetal tolerance, which turns into an increased sepsis risk after preterm delivery. Functional analyses are needed in order to elucidate whether Tregs have potential as future target for diagnostics and therapeutics.

Abstract 2646: Targeting cancer stem cell pathways with cell-permeable peptide inhibitors

Direct targeting of several important cancer pathways has so far proved challenging, owing to the lack of pathway-specific targets that can be accessed by conventional small molecule drugs or therapeutic antibodies. Nexigen develops and advances peptide-based cancer therapeutics, a new class of drugs that functionally modulate currently undruggable pathways by targeting intracellular protein-protein-interactions.

One of these undruggable pathways, the Wnt signaling cascade, has been identified as a key pathway in cancer stem cells maintenance. Targeting oncongenic Wnt signaling therefore holds great promise for tackling not only tumor growth but also disease relapse, metastasis and drug resistance. Using our proprietary next generation peptide screening system, we could identify cell-permeable peptides that efficiently inhibit the Wnt pathway through a specific interaction with a key component of intracellular signaling. Our most advanced preclinical candidate has nanomolar target affinity and significantly reduces the expression of Wnt target genes in triple-negative MDA-MB-231 breast cancer cells. The further functional analysis of the peptide in various cancer cell lines revealed a dose-dependent inhibition of cell migration, invasion, proliferation, and the cancer stem cell phenotype. The siRNA-mediated knock-down of the target protein or the inhibition of the Wnt pathway recapitulated the inhibitory peptide effect in these assays. Most importantly, we observed a significant suppression of primary tumor growth, tumor cell self-renewal and a reduction of metastatic potential after treatment in different xenograft models.

In summary, our data suggest that our Wnt pathway peptide inhibitor could be a promising new drug candidate for the treatment of cancer stem cells in a broad diversity of cancers.

Citation Format: Verena Arndt, Annette Friebe, Elena Meuser, Katharina Ross, Franziska Agerer, Carmen Schulten-Schulz, Jens Waak, Daniel Friedrich, Hanjo Hennemann, Jörg Vollmer. Targeting cancer stem cell pathways with cell-permeable peptide inhibitors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2646. doi:10.1158/1538-7445.AM2015-2646

Precise measurement of laser power using an optomechanical system

This paper shows a novel method to precisely measure the laser power using an optomechanical system. By measuring a mirror displacement caused by the reflection of an amplitude modulated laser beam, the number of photons in the incident continuous-wave laser can be precisely measured. We have demonstrated this principle by means of a prototype experiment uses a suspended 25 mg mirror as an mechanical oscillator coupled with the radiation pressure and a Michelson interferometer as the displacement sensor. A measurement of the laser power with an uncertainty of less than one percent (1σ) is achievable.