Rosette ribbon

Urea/Thiourea-Anion Host Lattices, Stabilization of Labile Species, and Designed Construction of Rosette Ribbon and Layers... 

Anionic Rosette Ribbon Built of Guanidinium and Hydrogen Carbonate Dimer... 

The rosette ribbon of 29 bears a strong resemblance to that of 28, except that the hydrogen-bonding pattern C is centrosymmetric and the spacing between neighboring parallel ribbons is increased to ca. 18.5 A (Figure 8.63). The independent GM+ cations,... 

Mak TCW, Xue F (2000) Supramolecular rosette ribbon construded from guanidium and hydrogen carbonate ions in the crystal engineering of hydrogen-bonded networks. J Am Chem Soc 122 9860... 

Rosettes, tapes (ribbons), fibers and two-dimensional networks... 

Projection diagram showing a portion of the nonplanar anionic rosette network I concentrated at a = 1/4 in the crystal structure of (1). The atom types are differentiated by size and shading, and hydrogen bonds are indicated by dotted lines. Adjacent antiparallel (VNI I2)31 1 C03 co ribbons run parallel to the b axis. Symmetry transformations A ( /2 — x, 1 — y,... 

Ependymoblastoma Like PNET ribbons/cords of cells true ependymal rosettes Vimentin (S) GFAP (R) Cerebrum cerebellum... 

The complementarity of some triaminotriazines (and related heterocycles) and barbituric acid was employed extensively in the assembly of a variety of discrete multicomponent structures as well as of extended ribbons, tapes, and rosettes (Scheme 3). A collection of strong hydrogen bonds can impart sufficient stability to allow these structures to stay intact in solution as well as in the gas phase. 

Figure 8.63 Perspective view of the hydrogen-bonded layer in 29 along the [110] direction. Linear ribbons of fused rosettes are interlinked by 4-nitrobenzoate ions through strong N -H- Cr (carboxylate) and weak C-H- -O(nitro) hydrogen bonding...

Figure 8.66 Projection along c showing the nearly planar guanidinium-carbonate (1 1) rosette network II at z = 1/2 in the crystal structure of 35. The atom types are differentiated by size and different grey scales, and N-H- O hydrogen bonds are represented by dotted lines. The layer is composed of independent carbonate ions [labeled by their central carbon atoms C(1) and C(3)[ andguanidinium ions [C(2) and C(4)[ in equal numbers. Note Mean atomic deviation from plane of one rosette = 0.36 A, and mean atomic deviation from plane of ribbon fragment [C(1), C(2), C(3), C(4)[ = 0.44 A]. Symmetry transformation a (1 — x, I + y, 1 - z)...

Figure 12-30. Structures of cellulose microfibrils synthesized by distinct TCs. Note cross sectional views of cellulose microfibrils (oblique lines) and particle arrangement of TCs on the fractured face of the plasma membrane. (A) A bundle consisting of 2-nm fine fibrils, which is synthesized by a dinoflagellate TC (a). (B) A thin, ribbon-like microfibril synthesized by each of phaeophycean and eustigmatophycean TCs (b), and rhodophycean (c), xanthophycean (d), and phaeothamniophycean TCs (e). (C) A large microfibril synthesized by each of ulvophycean (f), chlorophycean (g), and glau-cophycean TCs (h). (D) A 3.5-nm microfibril synthesized by a rosette TC (i). (E) A microfibril with a parallelogrammic section synthesized by a tunicate TC (j).

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