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Topological Arrangement (topological + arrangement)
Selected AbstractsCiliated band structure in planktotrophic and lecithotrophic larvae of Heliocidaris species (Echinodermata: Echinoidea): a demonstration of conservation and changeACTA ZOOLOGICA, Issue 3 2001M. Byrne Abstract The evolution of lecithotrophic (non-feeding) development in sea urchins is associated with reduction or loss of structures found in the planktotrophic (feeding) echinopluteus larvae. Reductions or losses of larval feeding structures include pluteal arms, their supporting skeleton and the ciliated band that borders them. The barrel-shaped lecithotrophic larva of Heliocidaris erythrogramma has, at its posterior end, two or three ciliated band segments comprised of densely packed, elongate cilia. These cilia may be expressions of the epaulettes that would have been present in an ancestral larval form, represented today by the feeding echinopluteus of H. tuberculata. We compared the development and cellular organization of the larval ciliary structures of both Heliocidaris species to assess whether the ciliary bands of H. erythrogramma are expressions of the feeding ciliated band or epaulettes of an echinopluteus. Epaulette development in feeding larvae of H. tuberculata involves separation of specific parts of the ciliated band from the rest of the feeding ciliated band, hyperplastic addition of ciliated cells and hypertrophic growth of the cilia. Like epaulettes, the ciliated bands of H. erythrogramma are composed of long spindle-shaped cells arranged in a cup-shaped collection that bulges into the blastocoel; and these cells have elongated cilia. In their developmental origin and topological arrangement however, the ciliated bands of H. erythrogramma correspond more closely with parts of the pluteal feeding ciliated band than with epaulettes. The larvae of this echinoid appear to develop epaulette-like bands from parts of the original (but reduced) feeding ciliated band. The evolution of development in H. erythrogramma has thus involved both conservation and change in echinopluteal ciliary structures. [source] Hydrogen-bonded zigzag chains in 2,2,-dithiodibenzoic acid,1,3-di-4-pyridylpropane (1/1)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2009Li-Li Wang The title 1:1 cocrystal, C14H10O4S2·C13H14N2 or H2L·bpp, has the two components connected by O,H...N hydrogen bonds to generate a one-dimensional zigzag chain running along the crystallographic a direction. These chains are further stacked into a three-dimensional supramolecular network by weak C,H...O and C,H..., contacts. Comparison of the structural differences with previous findings suggests that deprotonated forms, hydrogen-bonding sites and flexible ligand conformations become significant factors that influence the topological arrangement and binding stoichiometry of the resulting cocrystals. [source] Mainland colonization by island lizardsJOURNAL OF BIOGEOGRAPHY, Issue 6 2005Kirsten E. Nicholson Abstract Aim, We investigate biogeographic relationships within the lizard genus Anolis Daudin, 1802 to test the hypothesis that the mainland (Central and South American) Norops-clade species descended from a West Indian Anolis ancestor. Previous hypotheses have suggested that close island relatives of mainland Norops species (the Cuban Anolis sagrei and Jamaican A. grahami series) represent over-water dispersal from a mainland ancestor. These previous hypotheses predict that the A. sagrei and A. grahami series should be phylogenetically nested within a Norops clade whose ancestral geography traces to the mainland. If Norops is West Indian in origin, then West Indian species should span the deepest phylogenetic divergences within the Norops clade. Location, Central and South America and West Indian islands. Methods, The phylogenetic relationships of Anolis lizards are reconstructed from aligned DNA sequences using both parsimony and Bayesian approaches. Hypotheses are tested in two ways: (1) by reconstructing the ancestral geographic location for the Norops clade using Pagel & Lutzoni's (2002) Bayesian approach, and (2) by testing alternative topological arrangements via Wilcoxon Signed-Ranks tests (Templeton, 1983) and Shimodaira,Hasegawa tests (Shimodaira & Hasegawa, 1999). Results, Our evidence supports an origin of mainland Norops anoles from a West Indian ancestor. A West Indian ancestor to the Norops clade is statistically supported, and alternatives to the biogeographic pattern [Cuban (Jamaican, Mainland)] are statistically rejected by Shimodaira,Hasegawa tests, although not by Wilcoxon Signed-Ranks tests. Main conclusions, Our data support the hypothesis of a West Indian origin for mainland Norops. This result contradicts previous hypotheses and suggests that island forms may be an important source for mainland biodiversity. [source] Synthesis, conformational analysis and biological activities of lanthionine analogs of a cell adhesion modulatorJOURNAL OF PEPTIDE SCIENCE, Issue 2 2001Haitao Li Abstract Cell adhesion is critical for many biological processes, such as hemostasis, wound healing, tumor metastasis and inflammation. Integrins are important mediators of cell adhesion. The integrin ,4,1, also known as VLA-4, is a cell surface receptor involved in inflammation. A cyclic peptide, 1-FCA-Arg-c[Cys-Asp-Thz-Cys]-OH, is a potent antagonist to VLA-4 with an IC50 of 2.4 n,,. In the current study, we synthesized the lanthionine analogs of 1-FCA-Arg-c[Cys-Asp-Thz-Cys]-OH and determined the conformations of both the parent compound and its lanthionine analog in solution by NMR and computer simulations. The lanthionine analog retains its selectivity to VLA-4 with high nanomolar potency. Both molecules adopt similar topological arrangements in their conformations, while some important differences remain in the sulfur bridge region, which may cause the difference in potency. Copyright © 2001 European Peptide Society and John Wiley & Sons, Ltd. [source] | ||||||||||