Elucidating the Non-Covalent Interactions that Trigger Interdigitation in Lead-Halide Layered Hybrid Perovskites.

Two-dimensional (2D) hybrid organic-inorganic perovskites constitute a versatile class of materials applied to a variety of optoelectronic devices. These materials are composed of alternating layers of inorganic lead halide octahedra and organic ammonium cations. Most perovskite research studies so far have focused on organic sublattices based on phenethylammonium and alkylammonium cations, which are packed by van der Waals cohesive forces. Here, we report a more complex organic sublattice containing benzotriazole-based ammonium cations packed through interdigitated π-π stacking and hydrogen bonding. Single crystals and thin films of four perovskite derivatives are studied in depth with optical spectroscopy and X-ray diffraction, supported by density-functional theory calculations. We quantify the lattice stabilization of interdigitation, dipole-dipole interactions, and inter- as well as intramolecular hydrogen bonding. Furthermore, we investigate the driving force behind interdigitation by defining a steric occupancy factor σ and tuning the composition of the organic and inorganic sublattice. We relate the phenomenon of interdigitation to the available lattice space and to weakened hydrogen bonding to the inorganic octahedra. Finally, we find that the stabilizing interactions in the organic sublattice slightly improve the thermal stability of the perovskite. This work sheds light on the design rules and structure-property relationships of 2D layered hybrid perovskites.

Critical Role of Perovskite Film Stoichiometry in Determining Solar Cell Operational Stability: a Study on the Effects of Volatile A-Cation Additives.

Volatile A-cation halide (AX) additives such as formamidinium chloride and methylammonium chloride have been widely employed for high-efficiency perovskite solar cells (PSCs). However, it remains unstudied how they influence the perovskite film stoichiometry and the solar cell performance and operational stability. Hereby, our work shows that over annealing of formamidinium chloride-containing perovskite films leads to a Pb-rich surface, resulting in a high initial efficiency, which however decays during maximum power point tracking (MPPT). On the contrary, perovskite films obtained by a shorter annealing time at the same temperature provide good stability during MPPT but a lower initial efficiency. Thus, we deduce that an optimal annealing is vital for both high efficiency and operational stability, which is then confirmed in the case where methylammonium chloride additive is used. With optimized perovskite annealing conditions, we demonstrate efficient and stable p-i-n PSCs that show a best power conversion efficiency of 20.7% and remain 90% of the initial performance after a 200 h MPPT at 60 °C under simulated 1 sun illumination with high UV content. Our work presents a comprehensive understanding on how volatile AX impacts perovskite film stoichiometry and its correlation to the device performance and operational stability, providing a new guideline for fabricating high-efficiency and operationally stable PSCs.

Description of the nanostructured morphology of [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM) by XRD, DSC and solid-state NMR.

PCBM or [6,6]-phenyl-C(61)-butyric acid methyl ester is nowadays still one of the most successful electron acceptors for plastic bulk heterojunction (BHJ) photovoltaic devices. In this study, a set of complementary techniques, i.e. solid-state NMR, XRD and DSC, is proposed as a fast and sensitive tool to screen the morphology of PCBM specimens with different preparation histories. Based on proton NMR relaxation decay time values, an interval can be derived that situates the average crystal dimensions and which can further be refined on the basis of XRD patterns and DSC thermograms.

Defining Polysaccharide-Specific Antibody Targets against Vibrio cholerae O139 in Humans following O139 Cholera and following Vaccination with a Commercial Bivalent Oral Cholera Vaccine, and Evaluation of Conjugate Vaccines Targeting O139.

Cholera caused by Vibrio cholerae O139 could reemerge, and proactive development of an effective O139 vaccine would be prudent. To define immunoreactive and potentially immunogenic carbohydrate targets of Vibrio cholerae O139, we assessed immunoreactivities of various O-specific polysaccharide (OSP)-related saccharides with plasma from humans hospitalized with cholera caused by O139, comparing responses to those induced in recipients of a commercial oral whole-cell killed bivalent (O1 and O139) cholera vaccine (WC-O1/O139). We also assessed conjugate vaccines containing selected subsets of these saccharides for their ability to induce protective immunity using a mouse model of cholera. We found that patients with wild-type O139 cholera develop IgM, IgA, and IgG immune responses against O139 OSP and many of its fragments, but we were able to detect only a moderate IgM response to purified O139 OSP-core, and none to its fragments, in immunologically naive recipients of WC-O1/O139. We found that immunoreactivity of O139-specific polysaccharides with antibodies elicited by wild-type infection markedly increase when saccharides contain colitose and phosphate residues, that a synthetic terminal tetrasaccharide fragment of OSP is more immunoreactive and protectively immunogenic than complete OSP, that native OSP-core is a better protective immunogen than the synthetic OSP lacking core, and that functional vibriocidal activity of antibodies predicts in vivo protection in our model but depends on capsule thickness. Our results suggest that O139 OSP-specific responses are not prominent following vaccination with a currently available oral cholera vaccine in immunologically naive humans and that vaccines targeting V. cholerae O139 should be based on native OSP-core or terminal tetrasaccharide. IMPORTANCE Cholera is a severe dehydrating illness of humans caused by Vibrio cholerae serogroup O1 or O139. Protection against cholera is serogroup specific, and serogroup specificity is defined by O-specific polysaccharide (OSP). Little is known about immunity to O139 OSP. In this study, we used synthetic fragments of the O139 OSP to define immune responses to OSP in humans recovering from cholera caused by V. cholerae O139, compared these responses to those induced by the available O139 vaccine, and evaluated O139 fragments in next-generation conjugate vaccines. We found that the terminal tetrasaccharide of O139 is a primary immune target but that the currently available bivalent cholera vaccine poorly induces an anti-O139 OSP response in immunologically naive individuals.

Inkjet Printing of PEDOT:PSS Based Conductive Patterns for 3D Forming Applications.

This paper presents the formulation, inkjet printing, and vacuum forming of a conductive and stretchable polymer, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), ink on a stretchable and transparent thermoplastic polyurethane (TPU) substrate. The formulation of the conductive and stretchable ink is achieved by combining PEDOT:PSS with additional solvents, to achieve the right inkjet properties for drop-on-demand (DoD) inkjet printing. A conductive pattern can be printed from the 21 µm orifice on a flexible and stretchable TPU substrate, with a linewidth down to 44 µm. The properties of the printed pattern, in terms of sheet resistance, morphology, transparency, impact of weather conditions, and stretching are investigated and show sheet resistances up to 45 Ohm/sq and transparencies as high as 95%, which is comparable to indium tin oxide (ITO). Moreover, in contrast to ITO, one-time stretching up to 40% can be achieved, increasing the sheet resistance up to 214 Ohm/sq only, showing the great potential of this ink for one-time stretching. Finally, as a proof of this one-time stretching, the printed samples are vacuum formed around a 3D object, still showing sufficient conductivity to be applied as a capacitive touch sensor.

Application of a combined weak cation-exchange/crown ether column: first demonstrations of a versatile tool for proteome subselection.

The present paper introduces the use of a weak cation-exchange/crown ether column in the proteomics field. The 18-crown-6 ether functionality is well-known to selectively complex ammonium and monoalkylammonium ions, which should make this column highly suitable to trap peptides with free alpha-NH(2) or free epsilon-NH(2) groups from lysine side chains. This unique selection mechanism was put to the test in an N-teromics setup which aims for the enrichment of deliberately acetylated protein N-terminal peptides from a serum digest. It was demonstrated that peptides with free alpha-NH(2) groups and peptides with alpha-amino-acetylated groups can be separated from each other using this weak cation-exchange/crown ether column. The peptides of interest, bearing no free primary amines, were found to be significantly enriched in the column's flow through. At the same time a favorable coenrichment of N-glycosylated peptides was observed. To obtain more insight in the contributions of the two distinct column functionalities, i.e., the weak cation exchanger and the crown ether, the experimental data were checked against a theoretical prediction of the outcome.

Towards 2D layered hybrid perovskites with enhanced functionality: introducing charge-transfer complexes via self-assembly.

This study broadens the family of 2D layered perovskites by demonstrating that it is possible to self-assemble organic charge-transfer complexes in their organic layer. Organic charge-transfer complexes, formed by combining charge-donating and charge-accepting molecules, are a diverse class of materials that can possess exceptional optical and electronic properties.

Protease Substrate Profiling by N-Terminal COFRADIC.

Detection of (neo-)N-terminal peptides is essential for identifying protease cleavage sites . We here present an update of a well-established and efficient selection method for enriching N-terminal peptides out of peptide mixtures: N-terminal COFRADIC (COmbined FRActional DIagonal Chromatography). This method is based on the old concept of diagonal chromatography, which involves a peptide modification step in between otherwise identical chromatographic separations, with this modification step finally allowing for the isolation of N-terminal peptides by longer retention of non-N-terminal peptides on the resin. N-terminal COFRADIC has been successfully applied in many protease-centric studies, as well as for studies on protein alpha-N-acetylation and on characterizing alternative translation initiation events.

Selective Glucocorticoid Receptor Properties of GSK866 Analogs with Cysteine Reactive Warheads.

Synthetic glucocorticoids (GC) are the mainstay therapy for treatment of acute and chronic inflammatory disorders. Due to the high adverse effects associated with long-term use, GC pharmacology has focused since the nineties on more selective GC ligand-binding strategies, classified as selective glucocorticoid receptor (GR) agonists (SEGRAs) or selective glucocorticoid receptor modulators (SEGRMs). In the current study, GSK866 analogs with electrophilic covalent-binding warheads were developed with potential SEGRA properties to improve their clinical safety profile for long-lasting topical skin disease applications. Since the off-rate of a covalently binding drug is negligible compared to that of a non-covalent drug, its therapeutic effects can be prolonged and typically, smaller doses of the drug are necessary to reach the same level of therapeutic efficacy, thereby potentially reducing systemic side effects. Different analogs of SEGRA GSK866 coupled to cysteine reactive warheads were characterized for GR potency and selectivity in various biochemical and cellular assays. GR- and NFκB-dependent reporter gene studies show favorable anti-inflammatory properties with reduced GR transactivation of two non-steroidal GSK866 analogs UAMC-1217 and UAMC-1218, whereas UAMC-1158 and UAMC-1159 compounds failed to modulate cellular GR activity. These results were further supported by GR immuno-localization and S211 phospho-GR western analysis, illustrating significant GR phosphoactivation and nuclear translocation upon treatment of GSK866, UAMC-1217, or UAMC-1218, but not in case of UAMC-1158 or UAMC-1159. Furthermore, mass spectrometry analysis of tryptic peptides of recombinant GR ligand-binding domain (LBD) bound to UAMC-1217 or UAMC-1218 confirmed covalent cysteine-dependent GR binding. Finally, molecular dynamics simulations, as well as glucocorticoid receptor ligand-binding domain (GR-LBD) coregulator interaction profiling of the GR-LBD bound to GSK866 or its covalently binding analogs UAMC-1217 or UAMC-1218 revealed subtle conformational differences that might underlie their SEGRA properties. Altogether, GSK866 analogs UAMC-1217 and UAMC-1218 hold promise as a novel class of covalent-binding SEGRA ligands for the treatment of topical inflammatory skin disorders.

Synthesis of spacer-equipped phosphorylated di-, tri- and tetrasaccharide fragments of the O-specific polysaccharide of Vibrio cholerae O139.

The synthesis of oligosaccharide fragments of the O-specific polysaccharide of Vibrio cholerae O139 containing a 4,6-cyclic phosphate galactose residue linked to GlcNAc is described. 8-Azido-3,6-dioxaoctyl 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl-(1-->3)-2-acetamido-4,6-O-benzylidene-2-deoxy-beta-D-glucopyranoside, obtained by condensation of 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide and 8-azido-3,6-dioxaoctyl 2-acetamido-4,6-O-benzylidene-2-deoxy-beta-D-glucopyranoside, was converted to 8-azido-3,6-dioxaoctyl 3-O-benzyl-beta-D-galactopyranosyl-(1-->3)-2-acetamido-6-O-benzyl-2-deoxy-beta-D-glucopyranoside (6) by reductive opening of the acetal, followed by deacetylation and selective benzylation. Phosphorylation of 6 furnished two isomeric 4,6-cyclic 2,2,2-trichloroethyl phosphates. Glycosylation of the (S)-phosphate with 2,4-di-O-benzyl-3,6-dideoxy-alpha-L-xylo-hexopyranosyl bromide under halide-assisted conditions gave the desired tetrasaccharide, together with a trisaccharide. Global deprotection and reduction of the azide to an amine was effected by catalytic hydrogenation/hydrogenolysis to give the deprotected tetrasaccharide, which is functionalized for conjugation.

In-gel N-acetylation for the quantification of the degree of protein in vivo N-terminal acetylation.

Maturation of protein N-termini occurs in all kingdoms of life, with major protein modifications being proteolytic processing (e.g., removal of initiator methionines) and N-terminal acetylation. The functional consequences of these modifications are only known for a few substrates, and techniques to study such modifications have begun to emerge only recently. We here report on a method enabling targeted, mass spectrometry based analysis of protein N-termini from polyacrylamide gel-separated proteins. In our method, stable isotope incorporation by in-gel N-acetylation of free primary amines permits calculating the extent of in vivo N-terminal acetylation, proven to reveal crucial information with reference to N-terminal protein biology.

Controlled synthesis of ultrathin ZnO nanowires using micellar gold nanoparticles as catalyst templates.

We demonstrate a simple and effective approach to control the diameter of ultrathin ZnO nanowires with high aspect ratios and high densities over large areas. Diblock copolymer-based nanoparticle arrays exhibiting a high degree of hexagonal order and offering easy control of particle size (typically 1-10 nm) and interparticle spacing (25-150 nm) are utilized as nanocatalysts for the subsequent growth of semiconductor nanowires. The as-grown ZnO nanowires exhibit a single crystal hexagonal wurtzite structure and grow along the [0002] direction. Facetted catalyst particles were observed at the tip of the nanowires after synthesis, thus suggesting a catalyst-assisted vapor-solid-solid (VSS) rather than a vapor-liquid-solid (VLS) growth mechanism, the latter being frequently used in semiconductor nanowire production. Such a growth process allows us to easily prepare ultrathin ZnO nanowires with tunable diameters well below 10 nm by taking advantage of the inherent size control of the micellar method during deposition of the catalyst nanoparticles. Raman spectroscopy reveals a phonon confinement effect as the diameter of nanowires decreases. Photoluminescence spectra of these ultrathin nanowires indicate a blue shift of the free excitons and their phonon replicas by 37 meV induced by quantum confinement.

Compound A, a selective glucocorticoid receptor modulator, enhances heat shock protein Hsp70 gene promoter activation.

Compound A possesses glucocorticoid receptor (GR)-dependent anti-inflammatory properties. Just like classical GR ligands, Compound A can repress NF-κB-mediated gene expression. However, the monomeric Compound A-activated GR is unable to trigger glucocorticoid response element-regulated gene expression. The heat shock response potently activates heat shock factor 1 (HSF1), upregulates Hsp70, a known GR chaperone, and also modulates various aspects of inflammation. We found that the selective GR modulator Compound A and heat shock trigger similar cellular effects in A549 lung epithelial cells. With regard to their anti-inflammatory mechanism, heat shock and Compound A are both able to reduce TNF-stimulated IκBα degradation and NF-κB p65 nuclear translocation. We established an interaction between Compound A-activated GR and Hsp70, but remarkably, although the presence of the Hsp70 chaperone as such appears pivotal for the Compound A-mediated inflammatory gene repression, subsequent novel Hsp70 protein synthesis is uncoupled from an observed CpdA-induced Hsp70 mRNA upregulation and hence obsolete in mediating CpdA's anti-inflammatory effect. The lack of a Compound A-induced increase in Hsp70 protein levels in A549 cells is not mediated by a rapid proteasomal degradation of Hsp70 or by a Compound A-induced general block on translation. Similar to heat shock, Compound A can upregulate transcription of Hsp70 genes in various cell lines and BALB/c mice. Interestingly, whereas Compound A-dependent Hsp70 promoter activation is GR-dependent but HSF1-independent, heat shock-induced Hsp70 expression alternatively occurs in a GR-independent and HSF1-dependent manner in A549 lung epithelial cells.

Selecting protein N-terminal peptides by combined fractional diagonal chromatography.

In recent years, procedures for selecting the N-terminal peptides of proteins with analysis by mass spectrometry have been established to characterize protease-mediated cleavage and protein α-N-acetylation on a proteomic level. As a pioneering technology, N-terminal combined fractional diagonal chromatography (COFRADIC) has been used in numerous studies in which these protein modifications were investigated. Derivatization of primary amines--which can include stable isotope labeling--occurs before trypsin digestion so that cleavage occurs after arginine residues. Strong cation exchange (SCX) chromatography results in the removal of most of the internal peptides. Diagonal, reversed-phase peptide chromatography, in which the two runs are separated by reaction with 2,4,6-trinitrobenzenesulfonic acid, results in the removal of the C-terminal peptides and remaining internal peptides and the fractionation of the sample. We describe here the fully matured N-terminal COFRADIC protocol as it is currently routinely used, including the most substantial improvements (including treatment with glutamine cyclotransferase and pyroglutamyl aminopeptidase to remove pyroglutamate before SCX, and a sample pooling scheme to reduce the overall number of liquid chromatography-tandem mass spectrometry analyses) that were made since its original publication. Completion of the N-terminal COFRADIC procedure takes ~5 d.

Carbohydrate-based macrolides prepared via a convergent ring closing metathesis approach: in search for novel antibiotics.

An efficient convergent approach has been developed for the construction of novel, nonnatural polysubstituted carbohydrate-based macrolides. A key step in the synthesis is the formation of the macrocyclic ring via a ring-closing metathesis reaction. The obtained macrolide analogues have been screened for biological activity against gram-positive and gram-negative bacteria, yeasts, and molds.

Synthesis and screening of bicyclic carbohydrate-based compounds: a novel type of antivirals.

A small library of bicyclic carbohydrate derivatives was synthesized and screened. A strong and selective activity against cytomegalovirus was found. Structure-activity relationship for this new type of antivirals is discussed.

A convergent ring-closing metathesis approach to carbohydrate-based macrolides with potential antibiotic activity.

[reaction: see text] An efficient convergent approach has been developed for the construction of novel, non-natural, carbohydrate-based macrolides. The key step in the synthesis is the formation of the macrocyclic ring via a ring-closing metathesis reaction. The obtained macrolide analogues have been screened for biological activity against gram-positive and gram-negative bacteria, including resistant strains, yeasts, and molds.