Self-organization has been a key concept in various scientific research fields. A number of supramolecular architectures have been constructed by self-organization of appropriate tectons (the components that undergo self-assembly) by hydrogen bonds, electrostatic interactions, and coordination bonds. 1 Recently, oligonucleotides have attracted much attention as a "molecular glue" for supramolecular architectonics based on the selforganization concept. 2 Oligonucleotides are promising construction materials to array functional components in controlled space and direction, since DNA forms a linear, rigid double-strand helix by complementary hydrogen-bonded base-pairing. 2 Oligosaccharide chains, especially as glyco-clusters, on cell surfaces participate in various biological molecular recognitions and signal transductions through carbohydrate-binding proteins. 3 Various glycoconjugated polymers, 4-6 dendrimers, 7 calixarenes, 8 nanospheres, 9 and transition metal complexes 10 have been developed as glyco-cluster models and biomedical materials. It is well recognized that, if the intervals and directions of the carbohydrate ligands along the scaffolds can be controlled to fit strictly to the binding sites of the target carbohydrate-binding proteins, the binding ability of the glyco-clusters will be further enhanced. However, there has been no report for success in controlling the intervals and directions of the carbohydrate ligands. In this respect, it is of interest to apply DNA as a conformationally rigid scaffold of glyco-cluster models. Previously, we reported the preparation of covalent conjugates of multiple oligosaccharides attached to long DNA by a facile diazo-coupling method. 11 The conjugates acquired resistance to nucleases and strong recognizability to the corresponding lectin although the spaces between the oligosaccharides are random. This paper proposes a new strategy to construct periodic glycoclusters as illustrated in Figure 1. Site-specifically galactosylated oligonucleotide 20-mers 1-3 are synthesized and then hybridized with the half-sliding complementary oligonucleotide 5. "Halfsliding complementary DNA" has been proposed as an n-mer DNA, in which the right half sequence (red) and the left half sequence (blue) are respectively complementary to the left half sequence (red) and the right half sequence (blue) of the target n-mer DNA. Their hybridization is expected to produce the gapped heteroduplexes. The resulting nanometer-sized macromolecular periodic DNA framework will construct a comformationally rigid scaffold to display carbohydrates in defined orientations. The oligonucleotide 20-mers are designed to display the galactose residues at 68 Å (1 and 2) and 34 Å (3) regular intervals to the same direction from their DNA duplex, since B-form DNA duplex has an average of 10 base pairs and 34 Å pitch per turn of helix. Cumming, R.; Esko, J.; Freeze, H.; Hart, G.; Marth, J. Kobayashi, K.; Matsubara, N.; Muramatsu, T.; Suzuki, T.; Suzuki, Y. Glycoconjugate J. 1998, 15, 1014. (e) Dohi, H.; Nishid...

A GaN pyramid grown selectively on a (111)Si substrate with a patterned dot structure of a SiO2 mask, by metalorganic vapor phase epitaxy using AlGaN as an intermediate layer, was characterized by transmission electron microscopy. The dot pattern has an array of 5.0-μm-diameter window openings with a 10 μm period. The density of threading dislocations observed in the window region decreased gradually with increasing distance from the interface. This was mainly due to the dislocation reaction and bending of threading dislocations for the first 2 μm region from the interface and for the upper region, respectively. Dominantly observed defects in the lateral-growth part were dislocations parallel to the interface. An amorphous layer was formed at the interface in the window region. Nitride particles were observed at the interface in the mask region.

We describe herein the relationship between the spatial arrangement of self-organized galactose clusters and lectin recognition. beta-Galactose-modified deoxyuridine phosphoramidite was synthesized and applied to solid-phase synthesis to provide 18-, 20-, and 22-mers of site-specifically galactosylated oligodeoxynucleotides (Gal-ODNs). These Gal-ODNs were self-organized through hybridization with the corresponding 18-, 20-, and 22-mers of half-sliding complementary ODNs (hsc-ODNs) to give periodic galactoside clusters. The self-organization of ODNs was confirmed by size exclusion chromatography and gel electrophoresis. The binding of the Gal-clusters to the FITC-labeled RCA(120) lectin was analyzed by monitoring the change in fluorescence intensity. The assembly of 20-mer Gal-ODN with the 20-mer hsc-ODN was strongly and cooperatively recognized by the lectin. The 18-mer assembly was bound more weakly and less cooperatively, and the 22-mer assembly was minimally bound to the lectin. RCA(120) lectin recognized not only the density of galactoside residues, but also the spatial arrangement. The size of the Gal cluster was estimated from the association constant of Gal-ODN with hsc-ODN. The relationship between lectin-recognition and Gal-cluster size is also discussed.

Today's information-oriented society requires high density and high quality magnetic recording media. The quantitative observation of fine magnetic structures by electron holography is greatly anticipated in the development of such new recording materials. However, the magnetic fields around particles <50 nm have not been observed, because the fields are too weak to observe in the usual way. Here we present a highly precise phase measurement technique: improved phase-shifting electron holography. Using this method, the electric field around a charged polystyrene latex particle (100 nm in diameter) and the magnetic field around iron particles (30 nm in diameter) are observed precisely. A precision of the reconstructed phase image of 2pi/300 rad is achieved in the image of the latex particle.

Using transmission electron microscopy, we have characterized defect structures in laterally overgrown GaN crystals, grown directly on SiO2 stripe-patterned (111)Si substrates by metalorganic vapor phase epitaxy using AlGaN as an intermediate layer. The width and the period of the stripe windows were nominally 1 and 2 μm, respectively. The average threading dislocation density for a completely coalesced 2-μm-thick GaN crystal obtained on the [112̄]-oriented stripe-patterned substrate was ∼2×109 cm−2. The reduction in threading dislocation density is a consequence of the lateral growth and dislocation reactions at the coalesced front of the mask. On the other hand, valleys and pits tend to remain on the mask during the growth on the [11̄0]-oriented stripe-patterned substrate. Cracks were present in both crystals.