On-chip neo-glycopeptide synthesis for multivalent glycan presentation

Single glycan-protein interactions are often weak, such that glycan binding partners commonly utilize multiple, spatially defined binding sites to enhance binding avidity and specificity. Current array technologies usually neglect defined multivalent display. Laser-based array synthesis technology allows for flexible and rapid on-surface synthesis of different peptides. Combining this technique with click chemistry, we produced neo-glycopeptides directly on a functionalized glass slide in the microarray format. Density and spatial distribution of carbohydrates can be tuned, resulting in well-defined glycan structures for multivalent display. We probed the two lectins concanavalin A and langerin with different glycans on multivalent scaffolds, revealing strong spacing-, density-, and ligand-dependent binding. In addition, we could also measure the surface dissociation constant. This approach allows for a rapid generation, screening, and optimization of a multitude of multivalent scaffolds for glycan binding

Automated laser-transfer synthesis of high-density microarrays for infectious disease screening

Abstract Laser-induced forward transfer (LIFT) is a rapid laser-patterning technique for high-throughput combinatorial synthesis directly on glass slides. A lack of automation and precision limited LIFT applications to simple proof-of-concept syntheses of fewer than 100 compounds. Here, we report an automated synthesis instrument that combines laser transfer and robotics for parallel synthesis in a microarray format with up to 10000 individual reactions/cm2. An optimized pipeline for amide bond formation is the basis for preparing complex peptide microarrays with thousands of different sequences in high yield with high reproducibility. The resulting peptide arrays are of higher quality than commercial peptide arrays. More than 4800 15-residue peptides resembling the entire Ebola virus proteome on a microarray were synthesized to study the antibody response of an Ebola virus infection survivor. We identified known and unknown epitopes that serve now as a basis for Ebola diagnostic development. The versatility and precision of the synthesizer is demonstrated by in situ synthesis of fluorescent molecules via Schiff base reaction and multi-step patterning of precisely definable amounts of fluorophores. This automated laser transfer synthesis approach opens new avenues for high-throughput chemical synthesis and biological screening

A remote secondary binding pocket promotes heteromultivalent targeting of DC-SIGN

Dendritic cells (DC) are antigen-presenting cells coordinating the interplay of the innate and the adaptive immune response. The endocytic C-type lectin receptors DC-SIGN and Langerin display expression profiles restricted to distinct DC subtypes and have emerged as prime targets for next-generation immunotherapies and anti-infectives. Using heteromultivalent liposomes copresenting mannosides bearing aromatic aglycones with natural glycan ligands, we serendipitously discovered striking cooperativity effects for DC-SIGN+ but not for Langerin+ cell lines. Mechanistic investigations combining NMR spectroscopy with molecular docking and molecular dynamics simulations led to the identification of a secondary binding pocket for the glycomimetics. This pocket, located remotely of DC-SIGN’s carbohydrate bindings site, can be leveraged by heteromultivalent avidity enhancement. We further present preliminary evidence that the aglycone allosterically activates glycan recognition and thereby contributes to DC-SIGN-specific cell targeting. Our findings have important implications for both translational and basic glycoscience, showcasing heteromultivalent targeting of DCs to improve specificity and supporting potential allosteric regulation of DC-SIGN and CLRs in general

The role of hydrogen and fuel cells in the global energy system

Hydrogen technologies have experienced cycles of excessive expectations followed by disillusion. Nonetheless, a growing body of evidence suggests these technologies form an attractive option for the deep decarb onisation of global energy systems, and that recent improvements in their cost and performance point towards economic viability as well. This paper is a comprehensive review of the potential role that hydrogen could play in the provision of electricity, h eat, industry, transport and energy storage in a low - carbon energy system, and an assessment of the status of hydrogen in being able to fulfil that potential. The picture that emerges is one of qualified promise: hydrogen is well established in certain nic hes such as forklift trucks, while mainstream applications are now forthcoming. Hydrogen vehicles are available commercially in several countries, and 225,000 fuel cell home heating systems have been sold. This represents a step change from the situation of only five years ago. This review shows that challenges around cost and performance remain, and considerable improvements are still required for hydrogen to become truly competitive. But such competitiveness in the medium - term future no longer seems an unrealistic prospect, which fully justifies the growing interest and policy support for these technologies around the world

CellFy: A Cell-Based Fragment Screen against C-Type Lectins

Fragment-based drug discovery is a powerful complement to conventional high-throughput screening, especially for difficult targets. Screening low molecular weight fragments usually requires highly sensitive biophysical methods due to the generally low affinity of the identified ligands. Here, we de-veloped a cell-based fragment screening assay (cellFy) that allows sensitive identification of fragment hits in a physiologically more relevant environment in contrast to isolated target screenings in solution. For this a fluorescently labelled multivalent reporter was employed, enabling direct measurement of displacement by low molecular weight fragments without requiring enzymatic reactions or receptor activation. We applied this technique to identify hits against two challenging targets of the C-type lectin receptor (CLR) family: Dendritic Cell-Specific Intercellular adhesion molecule-3-Grabbing Non-integrin (DC-SIGN) and Langerin. Both receptors are involved in pathogen recognition and initiation of an immune response, which renders them attractive targets for immune modulation. Due to their shallow and hydrophilic primary binding site, hit identification for CLRs is challenging and drug-like ligands for CLRs are sparse. Screening of a fragment library followed by hit validation identified several promising candidates for further fragment evolution for DC-SIGN. Additionally, a multiplexed assay format was developed for simultaneous screening against multiple CLRs allowing a selectivity counterscreening. Overall, this sensitive cell-based fragment screening assay provides a powerful tool for rapid identification of bioactive fragments, even for difficult targets

Calcium-independent activation of an allosteric network in Langerin by heparin oligosaccharides

The C-type lectin receptor Langerin is a glycan binding protein that serves as an uptake receptor on Langerhans cells and is essential for the formation of Birbeck granules. Whereas most of Langerin´s ligands are recognized via a canonical Ca2+-dependent binding site, interactions with heparins have been proposed to make additional contacts to a secondary, Ca2+-independent site. Glycan array screening and biomolecular NMR spectroscopy were employed to investigate the molecular mechanism of these interactions. We observed that binding of heparin hexasaccharides to a secondary site does not require the presence of Ca2+ and activates a previously identified intradomain allosteric network of Langeri

Metadata Enrichment of Multi-disciplinary Digital Library: A Semantic-Based Approach

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