Calix  resorcarene-based macrocyclic glycocluster amphiphiles irreversibly form 5-nm sized micellar nanoparticles (GNPs) in water. They are agglutinated with Na2HPO4 via sugar-to-phosphate hydrogen-bonding and also assembled on plasmid DNA in a number-, size-, and shape-controlled manner to give artificial glycoviruses of a size of 50nm, which, depending on the saccharide moieties involved, are further aggregated. The glycoviruses are capable of endocytosis-mediated transfection of cell cultures, where only monomeric glycovirus undergoes size-allowed endocytosis. The optimal size at -50nm for endocytic cellular uptake is confirmed by competition using GNP (5nm) and a glycocluster conjugate of CdSe quantum dot (15nm) together with glycovirus (50nm) as size probes. The growth of glycocluster amphiphile through nanoparticle to glycovirus reveals a hierarchical adhesion control of the saccharide clusters.
Schizophyllan (SPG) is a polysaccharide that belongs to the β-(1-3) glucan family and adopts a triple-helixical conformation in water. When SPG dissolves in dimethyl sulfoxide (DMSO), the triple helix is dissociated to three random coils. When water is added to the DMSO solution (renaturation), the single chain of SPG (s-SPG) collapses owing to both hydrophobic interaction and hydrogen bonding formation, and eventually aggregation takes place with increasing the water content. When this renaturation process is carried out in a mixture containing s-SPG and a single-stranded polynucleotide, a macromolecular complex is formed, consisting of two s-SPG chains and one polynucleotide chain. This novel complexation was examined with circular dichroism, UV spectroscopy, and gel electrophoresis. We applied to this complex to deliver functional oligonucleotides such as antisense DNA and CpG motifs. The biological functions of these oligonucleotides were extremely enhanced owing to the complexation.
Obviously, human oligosaccharides and their mimics possess high potential in applications to medicines and biomaterials. On the other hand, it holds true that the high potential stems from the rather complicated and labile chemical structures. Therefore, it is of major significance to elucidate the key structures encoded in the oligosaccharides for making effective “minimization” and “functionalization.” Moreover, the glycosidic linkages labile to acids and glycosidases may give problems to practical applications. In this review, we wish to describe our mimetic design of the cell surface oligosaccharides based on “key carbohydrate modules” and “carbohydrate module method.”
Catalytic cleavage reactions by glucoamylase or phosphorylase b were monitored directly on an amylopectin-immobilized 27MHz quartz-crystal microbalance (QCM). As a first example, we could follow kinetically the enzyme binding to the substrate binding (kon) and dissociation rate constants (koff) and intramolecular hydrolysis rate constant (kcat) of glucan hydrolysis by glucoamylase by detecting directly the formation and decomposition of the enzyme-substrate (ES) complex as mass changes. Secondly, glucan phosphorolysis by phosphorylase b was directly observed by two methods through reactions on a QCM. All kinetic parameters for the enzyme binding to the substrate kon and koff, and dissociation constant, Kd, the AMP binding to the enzyme as activator (KAMP), and the catalytic rate constant (kcat) were obtained from curve fittings of time-courses of frequency (mass) changes. The obtained kinetic parameters were compared with those from Michaelis-Menten kinetics in the bulk solution.