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We describe the synthesis of the first heteroglycoclusters featuring three distinct carbohydrate ligands. The obtained pair of stereoisomeric glycoclusters were named "focal point enantiomers", as the configuration of the focal point is the only varying stereogenic element in these molecules. The first pair of such diastereomeric heteroglycoclusters was accessible by an efficient sequence of protection and sequential glycosylation steps utilizing a mannosyl, a N‐acetylglucosaminyl, and a galactosyl donor, respectively, which was applied to a prototype azido‐functionalized tris(hydroxymethyl)aminomethane (TRIS) scaffold molecule. The stereoisomers could be distinguished based on an X‐ray structure of one of the isomeric key intermediates. As previously shown with divalent counterparts, such heterotrivalent cluster glycosides are useful tools for studying the fine‐tuning of carbohydrate recognition. The azido functional group at the focal point of the synthetic scaffold molecule was employed in a conjugation reaction with a linker for further immobilization on a gold surface in order to fabricate glyco‐SAMs (self‐assembled monolayers). A preliminary biological evaluation of the focal point enantiomers was performed in solution using the well‐known model lectin Concanavalin A and the important bacterial lectin FimH. [ABSTRACT FROM AUTHOR]

Semiconductor nanocrystals (NCs) or quantum dots (QDs) are luminous point emitters increasingly being used to tag and track biomolecules in biological/biomedical imaging. However, their intracellular use as highlighters of single-molecule localization and nanobiosensors reporting ion microdomains changes has remained a major challenge. Here, we report the design, generation and validation of FRET-based nanobiosensors for detection of intracellular Ca2+ and H+ transients. Our sensors combine a commercially available CANdot®565QD as an energy donor with, as an acceptor, our custom-synthesized red-emitting Ca2+ or H+ probes. These 'Rubies' are based on an extended rhodamine as a fluorophore and a phenol or BAPTA (1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid) for H+ or Ca2+ sensing, respectively, and additionally bear a linker arm for conjugation. QDs were stably functionalized using the same SH/maleimide crosslink chemistry for all desired reactants. Mixing ion sensor and cell-penetrating peptides (that facilitate cytoplasmic delivery) at the desired stoichiometric ratio produced controlled multi-conjugated assemblies. Multiple acceptors on the same central donor allow up-concentrating the ion sensor on the QD surface to concentrations higher than those that could be achieved in free solution, increasing FRET efficiency and improving the signal. We validate these nanosensors for the detection of intracellular Ca2+ and pH transients using live-cell fluorescence imaging. [ABSTRACT FROM AUTHOR]

Chondroitin sulfate-E (CS-E) oligosaccharidic analogues (di to hexa) were prepared from lactose. In these compounds, the 2-acetamido group was replaced by a hydroxyl group. This modification speeded up the synthesis, and large oligosaccharides were constructed in a few steps from a lactose-originated block. The protecting groups used were as follows; Fmoc for hydroxyl groups to be glycosylated, allyl group for anomeric position protection, and trichoroacetimidate leaving groups were used to prepare up to octasaccharides. We took advantage of the presence of allyl group to develop a click biotinylation, through its transformation into a 3-azido-2-hydroxyl propyl group in two steps (epoxidation and sodium azide epoxide opening). The biotinylating agent was a water-soluble propargylated and biotinylated triethylene glycol (PEG). By using surface plasmon resonance (SPR), it was shown that the di-, tetra-, and hexasaccharides display a binding affinity and selectivity toward HSF/GSF and CXCL12 similar to that of CS-E. A parallel study confirmed their mimicry of natural compounds, based on the hexasaccharide interaction with Otx2, a homeodomain protein involved in brain maturation, thus validating our simplification approach to synthesize bioactive GAG. [ABSTRACT FROM AUTHOR]

Combining triflic acid-catalyzed acetalation, benzylation, reductive ring opening of benzylidene acetal and glycosylation in one-pot transformations leads to a wide range of d-glucosamine building blocks for assembling oligomers. [ABSTRACT FROM AUTHOR]