A novel bioorthogonal method for the modification of cells with single-stranded DNA oligomers is compared to five alternative methods with respect to labeling efficacy, specificity, and effects on cell viability. The new method is based on oxime ligation of aminooxybiotin to aldehyde groups installed by periodate cleavage of cell-surface glycans, followed by the coupling of preformed DNA-streptavidin conjugates. As compared with two literature-reported methods based on direct coupling of N-hydroxysuccinimidyl (NHS)-DNA or NHS-biotinylation as well as with techniques based on strain-promoted alkyne-azide cycloaddition, this method shows the highest labeling densities and is sufficiently mild to avoid cell damage. Functionality of the DNA tags is demonstrated by DNA-directed immobilization on solid substrates and assembly of small cell aggregates.

We report the tandem Staudinger/aza‐Wittig/Ugi three‐component reaction mediated synthesis of a 64‐member compound library of aza‐C‐glycosides. The library is composed of four pyrrolidine and three piperidine scaffolds, onto which a number of functional groups is grafted to form seven sublibraries. Variation in the library is achieved by transformation of two pentoses and a hexose into the corresponding 4‐azidopentanal and 5‐azidohexanal derivatives as precursors for the Staudinger/aza‐Wittig process. Further variation is achieved by using different isocyanides as well as protective‐ and functional‐group manipulations on the fully protected Ugi‐3CR intermediates. Preliminary biological evaluation of the compound library revealed several low micromolar inhibitors of human acid glucosylceramidase.

Large supramolecular protein complexes, such as the molecular machinery involved in gene regulation, cell signaling, or cell division, are key in all fundamental processes of life. Detailed elucidation of structure and dynamics of such complexes can be achieved by reverse-engineering parts of the complexes in order to probe their interactions with distinctive binding partners in vitro. The exploitation of DNA nanostructures to mimic partially assembled supramolecular protein complexes in which the presence and state of two or more proteins are decisive for binding of additional building blocks is reported here. To this end, four-way DNA Holliday junction motifs bearing a fluorescein and a biotin tag, for tracking and affinity capture, respectively, are site-specifically functionalized with centromeric protein (CENP) C and CENP-T. The latter serves as baits for binding of the so-called KMN component, thereby mimicking early stages of the assembly of kinetochores, structures that mediate and control the attachment of microtubules to chromosomes in the spindle apparatus. Results from pull-down experiments are consistent with the hypothesis that CENP-C and CENP-T may bind cooperatively to the KMN network.

The cover shows the modification of living cells with single‐stranded DNA oligonucleotides. The method described by C. M. Niemeyer and co‐workers takes advantage of covalent modification of carbohydrate residues of membrane proteins, which are abundant on the surface of eukaryotic cells. Cis‐diols of these carbohydrates are oxidatively cleaved to generate a carbonyl group, which undergoes a chemoselective oxime ligation with aminooxybiotin to produce biotinylated proteins. These are targeted by streptavidin covalently conjugated with DNA oligonucleotides. This method outperforms alternative chemistries for DNA coupling to cell surfaces because of its high labeling efficacy, specificity, and low impact on cell viability.

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