Altering the Modular Architecture of Galectins Affects its Binding with Synthetic α-Dystroglycan O-Mannosylated Core M1 Glycoconjugates In situ.

The multifunctionality of galectins helps regulate a broad range of fundamental cellular processes via cis-binding and trans-bridging activities and has gained widespread attention with respect to the importance of the natural specificity/selectivity of this lectin family to its glycoconjugate receptors. Combining galectin (Gal)-1, -3, -4, and -9 variant test panels, achieved via rational protein engineering, and a synthetic α-dystroglycan (DG) O-Mannosylated core M1 glycopeptide library, a detailed comparative analysis was performed, utilizing microarray experiments to delineate the design-functionality relationships within this lectin family. Enhancement of prototype Gal-1 and chimera-type Gal-3 cis-binding toward the prepared ligands is possible by transforming these lectins into tandem-repeat type and prototypes, respectively. Furthermore, Gal-1 variants demonstrated improved trans-bridging capabilities between core M1 α-DG glycopeptides and laminins in microarray, suggesting the possible translational applications of these galectin variants in the treatment of some forms of α-dystroglycanopathy.

Exploring the In situ pairing of human galectins toward synthetic O-mannosylated core M1 glycopeptides of α-dystroglycan.

Dystroglycan (DG), which constitutes a part of the dystrophin-glycoprotein complex, connects the extracellular matrix to the cytoskeleton. The matriglycans presented by the extracellular α-DG serve as a contact point with extracellular matrix proteins (ECM) containing laminin G-like domains, providing cellular stability. However, it remains unknown whether core M1 (GlcNAcß1-2Man) structures can serve as ligands among the various O-Mannosylated glycans. Therefore, based on the presence of N-acetylLactosamine (LacNAc) in this glycan following the core extension, the binding interactions with adhesion/growth-regulatory galectins were explored. To elucidate this process, the interaction between galectin (Gal)-1, -3, -4 and -9 with α-DG fragment 372TRGAIIQTPTLGPIQPTRV390 core M1-based glycopeptide library were profiled, using glycan microarray and nuclear magnetic resonance studies. The binding of galectins was revealed irrespective of its modular architecture, adding galectins to the list of possible binding partners of α-DG core M1 glycoconjugates by cis-binding (via peptide- and carbohydrate-protein interactions), which can be abrogated by α2,3-sialylation of the LacNAc units. The LacNAc-terminated α-DG glycopeptide interact simultaneously with both the S- and F-faces of Gal-1, thereby inducing oligomerization. Furthermore, Gal-1 can trans-bridge α-DG core M1 structures and laminins, which proposed a possible mechanism by which Gal-1 ameliorates muscular dystrophies; however, this proposal warrants further investigation.

Protecting group-free method for synthesis of N-glycosyl carbamates and an assessment of the anomeric effect of nitrogen in the carbamate group.

The first protecting group-free synthesis of N-glycosyl carbamates has been developed through reaction of d-glucose with n-butyl carbamate in acidic aqueous media. The structures of the N-glucosyl carbamates were unambiguously determined by comparison with authentic samples, prepared using the isocyanide method. With this protective group-free method for synthesis of N-glycosyl carbamates in hand, an anomeric pair of N-xylopyranosyl carbamates were prepared and used to assess the anomeric effect of nitrogen in the carbamate group.

Synthesis and Self-Assembly Properties of Bola-Amphiphilic Glycosylated Lipopeptide-Type Supramolecular Hydrogels Showing Colour Changes Along with Gel-Sol Transition.

Supramolecular hydrogels formed by self-assembly of low-molecular-weight amphiphiles (hydrogelators) have attracted significant attention, as smart and soft materials. However, most of the observed stimuli-responsive behaviour of these supramolecular hydrogels are limited to gel-sol transitions. In this study, we present bola-amphiphilic glycosylated lipopeptide-type supramolecular hydrogelators that exhibit reversible thermochromism along with a gel-sol transition. The bola-amphiphiles have mono-, di-, tri- or tetra-phenylalanine (F) as a short peptide moiety. We investigate and discuss the effects of the number of F residues on the gelation ability and the morphology of the self-assembled nanostructures.

Structural diversification of bola-amphiphilic glycolipid-type supramolecular hydrogelators exhibiting colour changes along with the gel-sol transition.

We diversified the structures of bola-amphiphilic glycolipid-type supramolecular hydrogelators that exhibited reversible thermochromism along with a gel-sol transition. The hydrogelators were designed and synthesized to have homo- or hetero-saccharides on each end of their molecules. Herein, the effects of the saccharides' structure on the gelation ability are discussed.

Synthetic glycopeptides reveal specific binding pattern and conformational change at O-mannosylated position of α-dystroglycan by POMGnT1 catalyzed GlcNAc modification.

Structural and functional effects of core M1 type glycan modification catalyzed by protein O-linked mannose ß1,2-N-acetylglucosaminyltransferase 1 (POMGnT1) were investigated using a core M1 glycoform focused library of an α-dystroglycan fragment, 372TRGAIIQTPTLGPIQPTRV390. Evanescent-field fluorescence-assisted microarray system illuminated the specific binding pattern of plant lectins that can discriminate the glycan structure of core M1 glycan of the library. The comparative NMR analysis of synthetic glycopeptide having different length of the O-mannosylated glycans revealed a conformational change of the peptide backbone along with core M1 disaccharide formation. No long-range NOE signals of glycan-amino acid nor inter amino acid indicate the conformational change is induced by steric hindrance of core M1, the sole 1,2-O-modified form among protein binding sugar residue found in mammals.

A Zn(ii) metal-organic framework with dinuclear [Zn2(N-oxide)2] secondary building units.

We report the synthesis, structural characterisation, and adsorption properties of a three-dimensional metal-organic framework [Zn(pydcao)(DMF)] (H2-pydcao = 3,5-pyridinedicarboxylic acid N-oxide) that has an unprecedented [Zn2(N-oxide)2] secondary building unit.

Transition-metal-catalyzed divergent functionalization of [60]fullerene with propargylic esters.

We have demonstrated that transition-metal-catalyzed divergent reactions between [60]fullerene (C60) and propargylic esters allow easy access to formal [2 + 2] and [4 + 2] cycloadducts in reasonable yields, and that the production ratios depend on the metal catalyst used. The molecular structures of the cycloadducts were characterized by means of spectroscopic analyses and theoretical calculations. A plausible reaction mechanism is proposed that shows that two competing routes are likely to be involved after the initial transition-metal-activated cyclization of the carbonyl group and the C-C triple bond in the 6-endo-dig mode. Further rearrangement into allenol esters followed by formal [2 + 2] cycloaddition with C60 gives the [2 + 2] cycloadducts, whereas rearrangement into 1,3-dienyl esters followed by [4 + 2] cycloaddition with C60 gives the [4 + 2] cycloadducts.

A Highly Water-Tolerant Magnesium(II) Coordination Polymer Derived from a Flexible Layered Structure.

A two-dimensional (2D) layered Mg(II) coordination polymer (CP) with a high tolerance for H2 O was designed, synthesised, and crystallographically characterised. The synthesis was achieved by the introduction of a flexible 2D layered structure composed of Mg(II) ions and isonicotinate N-oxide ligands. Owing to its high H2 O tolerance, the obtained 2D layered structure has the flexibility to repeatedly adsorb a large amount of H2 O associated with interlayer expansion and enable the removal of H2 O from a H2 O/2-propanol mixed vapour. These results indicate that the CP could be an excellent dehydrating agent.

Design of peptide-based bolaamphiphiles exhibiting heat-set hydrogelation via retro-Diels-Alder reaction.

Supramolecular hydrogels have attracted much attention as smart soft materials. To install various stimuli-responsive functions in the supramolecular hydrogels, skilful utility of chemical reactions for triggering the change in molecular structure of hydrogelators or their precursor in response to external stimuli is a promising strategy. We have recently developed a unique heat-set supramolecular hydrogel, which was triggered by rationally designed molecular conversion of a glycolipid-based bolaamphiphile into a hydrogelator via retro-Diels-Alder reaction. Here we designed new bolaamphiphiles based on short peptide-based hydrogelators as a scaffold to accelerate the heat-set hydrogelation process and also demonstrated the flexible molecular design of such bolaamphiphiles.

Supramolecular hydrogels based on bola-amphiphilic glycolipids showing color change in response to glycosidases.

We developed supramolecular hydrogels exhibiting reversible thermochromism concurrently with gel-to-sol transition from four glycolipids. In addition, these gels showed the similar color change in response to glycosidases, which can be employed to construct a colorimetric sensor array chip for sensing glycosidases with the naked eye.

Heat-induced morphological transformation of supramolecular nanostructures by retro-Diels-Alder reaction.

Controlling the morphology of supramolecular nanostructures in response to external stimuli is an important challenge in the development of functional soft materials. Here we show that a morphological transformation from 2D nanosheets to a network of 1D nanofibers is triggered by heating, which induces molecular conversion of a bolaamphiphile to a hydrogelator by means of a retro-Diels-Alder reaction, thereby producing a new heat-set supramolecular hydrogel. We anticipate that our design will be a starting point for more sophisticated supramolecular systems that integrate the thermodynamics of molecular assembly and the kinetics of chemical reactions to create complex supramolecular nanostructures.

Effect of heat exposure on aminophylline-induced convulsions in mice.

Theophylline-associated convulsions are frequently exacerbated by fever, but the mechanisms behind it are still not completely understood. We investigated whether N-methyl-D-aspartic acid (NMDA) and gamma aminobutyric acid (GABA) receptors are involved in aminophylline (theophylline-2-ethylenediamine)-induced convulsions that are augmented by heat exposure-induced hyperthermia in mice. Mice exposed to 33 °C temperatures for 2 h had significantly increased body temperature (0.94 °C). Heat exposure significantly decreased time required for the onset of convulsions induced by an intraperitoneal (i.p.) injection of aminophylline (300 mg/kg). The shortened time for onset of convulsions was blocked by the NMDA receptor antagonist dizocilpine (0.1, 0.3 mg/kg, i.p.). However, the GABA(A) receptor agonist muscimol (1, 2 mg/kg, i.p.) did not have any effect. The pro-convulsant action of NMDA (100-125 mg/kg, i.p.) was enhanced by the heat exposure of 33 °C. However, the pro-convulsant actions of picrotoxin (3-4 mg/kg, i.p.), a GABA(A) receptor antagonist, were not affected by increased temperatures. These results suggest that NMDA receptors in the brain play a role in aminophylline-induced convulsions, which are augmented by heat exposure-induced hyperthermia in mice.

Supramolecular hydrogel-based protein and chemosensor array.

The development of protein and sensor arrays is crucial for rapid and high-throughput assays of biological events, markers, environmental pollutants, and others. We describe supramolecular hydrogel as a unique material for use as a matrix for immobilizing proteins, peptides, substrates, chemosensors, and mesoporous silica particles, and thereby array them on solid supports. The semi-wet conditions provided by the gel, which consists of 3D supramolecular nanofiber network structure, are suitable for entrapping such substances whilst retaining their activity and function. Moreover, the hydrophobic interior of the nanofibers of the supramolecular hydrogel can reversibly entrap hydrophobic molecules, which allows the development of various read-out systems, such as fluorescence enhancement and fluorescence resonance energy transfer (FRET), by which one can monitor the signal changes associated with, for instance, molecular recognition and enzyme activity.

Effect of Brewer's yeast-induced pyrexia on aminophylline-elicited convulsions in mice.

Theophylline-associated convulsions have been observed most frequently in children with fever, but the mechanism is not fully understood. In this study, we investigated the basic mechanism of aminophylline [theophylline-2-ethylenediamine]-induced convulsions and the effects of Brewer's yeast-induced pyrexia in mice. Diazepam (5-10mg/kg, i.p.), a benzodiazepine receptor agonist, significantly prolonged the onset and significantly decreased the incidence of convulsions induced by aminophylline (350 mg/kg, i.p.). However, the gamma aminobutyric acid (GABA)A receptor agonist muscimol (1-4 mg/kg, i.p.), the GABAB receptor agonist baclofen (2-4 mg/kg, i.p.) and the N-methyl-D-aspartic acid receptor antagonist dizocilpine (0.1-0.3 mg/kg, i.p.) failed to protect against the convulsions. 20% Brewer's yeast (0.02 ml/g, s.c.) increased body temperature by 1.03, and also significantly shortened the onset and significantly increased the incidence of convulsions induced by aminophylline. The anticonvulsant action of diazepam (2.5-10mg/kg, i.p.) on the convulsions induced by aminophylline was reduced by Brewer's yeast-induced pyrexia. The proconvulsant actions of the GABAA receptor antagonists picrotoxin (3-4 mg/kg, i.p.) and pentylenetetrazol (40-60 mg/kg, i.p.) were enhanced by Brewer's yeast. These results suggest that the anticonvulsant action of diazepam against aminophylline is reduced by Brewer's yeast-induced pyrexia, and that GABAA receptors are involved in the aggravation of the convulsions by Brewer's yeast in mice.