Probing Carbohydrate-Lectin Recognition in Heterogeneous Environments with Monodisperse Cyclodextrin-Based Glycoclusters

Abstract

A series of β-cyclodextrin (βCD)-scaffolded glycoclusters exposing heterogeneous yet perfectly controlled displays of α-mannosyl (α-Man) and β-lactosyl (β-Lact) antennas were synthesized to probe the mutual influence of varying densities of the saccharide motifs in the binding properties toward different plant lectins. Enzyme-linked lectin assay (ELLA) data indicated that the presence of β-Lact residues reinforced binding of α-Man to the mannose-specific lectin concanavalin A (Con A) even though homogeneous β-Lact clusters are not recognized at all by this lectin, supporting the existence of synergic recognition mechanisms (heterocluster effect). Conversely, the presence of α-Man motifs in the heteroglycoclusters also resulted in a binding-enhancing effect of β-Lact toward peanut agglutinin (PNA), a lectin strongly binding multivalent lactosides but having no detectable affinity for α-mannopyranosides, for certain architectural arrangements. Two-site, sandwich-type ELLA data corroborated the higher lectin clustering efficiency of heterogeneous glycoclusters compared with homogeneous displays of the putative sugar ligand with identical valency. A turbidity assay was also consistent with the previous observations. Most revealingly, the lectin cross-linking ability of heterogeneous glycoclusters was sensitive to the presence of high concentrations of the non-ligand sugar, strongly suggesting that "mismatching" saccharide motifs may modulate carbohydrate-lectin specific recognition in a lectin-dependent manner when present in highly dense displays together with the "matching" ligand, a situation frequently encountered in biological systems.

Dual drug-loaded halloysite hybrid-based glycocluster for sustained release of hydrophobic molecules

“…32 Since the dissociation constants of carbohydratelectin complexes are in the millimolar range, multivalent systems (which involve the simultaneous binding of multiple ligands onto multiple receptors) are required for efficient recognition (glycocluster effect).…”

Cyclodextrin-based multivalent glycodisplays: covalent and supramolecular conjugates to assess carbohydrate–protein interactions

“…87 García Fernández, Defaye, Ortiz Mellet and coworkers exploited the thiourea-forming reaction as the key step in the preparation of a series of 21-valent hyperbranched homo and heteroglycoclusters with aMan, bGlc and bLac glycotopes intended to assess the effect of highly dense heterogeneous glycoenvironments in the recognition of sugar ligands by specific lectins. 102,103,113 The isothiocyanate-armed trivalent heteroglycodendron building blocks were synthesized by sequential thiol-ene coupling onto triallylated pentaerythritol followed by functional group manipulation. After conjugation with per-(C-6)-amino bCD 22 and deacetylation of the adducts, all combinations of (aMan) 7n (bGlc or bLac) 7m (m + n = 3) were obtained (Scheme 28).…”

Multivalency in heterogeneous glycoenvironments: hetero-glycoclusters, -glycopolymers and -glycoassemblies

“…The methodology involves the use of two functionalized phosphoramidite derivatives, one bearing a bromoalkyl group as precursor of azide and another one that bears a clickable propargyl group. Both were incorporated into an oligonucleotide by phosphoramidite chemistry on a DNA synthesizer (30). After a first CuAAC cycle with a monosaccharide-azide derivative, the bromo groups are substituted by azide anion and a second CuAAC reaction with a different propargylated sugar was performed.…”

“…The results reflected unexpectedly high Con A-binding affinities for the mixed-type aMan/bGlc and aMan/ bLact heteroglycoclusters in comparison with homoglycoclusters with identical mannose valency. 29,30,56 The authors hypothesized the existence of a ''heterocluster effect'' that cannot be explained in terms of a difference in effective epitope concentration. To confirm the above results, the binding properties of highand low-density homo-and heteroglycoclusters with aMan and bGlc residues towards Con A lectin were assessed by using a range of competitive and non-competitive binding assays including ELLA, ITC and surface plasmon resonance (SPR).…”