Topological Knots
Mostrando 1-12 de 12 artigos, teses e dissertações.
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1. NÓS LEGENDREANOS EM R3 E O NÚMERO MÁXIMO E THURSTON-BENNEQUIN PARA NÓS DE 2 PONTES / LEGENDRIAN KNOTS AND THE MAXIMAL THURSTON-BENNEQUIN NUMBER OF TWO-BRIDGE KNOTS
O propósito deste trabalho é apresentar a teoria dos nós legendreanos, que diz respeito a nós tangentes a uma estrutura de contato, assim como demonstrar o Teorema do Número Máximo de Thurston- Bennequin para nós de 2-pontes em termos do polinômio de Kaumman. Iniciamos este trabalho com uma introdução aos nós topológicos. Apresentamos a teoria de
Publicado em: 2007
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2. NÓS LEGENDREANOS EM T3 / LEGENDRIAN KNOTS IN T3
Nesse trabalho apresentamos os nós legendreanos numa variedade M de dimensão 3 destacando as estruturas de contato canõnicas em R3 e T3. Para o primeiro caso estudamos os invariantes clássicos: Números de Thurston-Bennequin e Maslov. No segundo caso o número de Maslov é facilmente estendido para esse contexto, mas para o número de Thurston-Bennequin
Publicado em: 2007
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3. A topological invariant to predict the three-dimensional writhe of ideal configurations of knots and links
We present herein a topological invariant of oriented alternating knots and links that predicts the three-dimensional (3D) writhe of the ideal geometrical configuration of the considered knot/link. The fact that we can correlate a geometrical property of a given configuration with a topological invariant supports the notion that the ideal configuration conta
The National Academy of Sciences.
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4. Genetic rearrangement of DNA induces knots with a unique topology: implications for the mechanism of synapsis and crossing-over.
We have determined the topological sign of the knots produced by a cycle of phage lambda integrative recombination. To insure that these knots reflect intrinsic features of the reaction mechanism, the substrate was constructed so that random interwrapping of segments of DNA played a minimal role in the topological outcome. The knotted DNA was coated with the
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5. Novel topologically knotted DNA from bacteriophage P4 capsids: studies with DNA topoisomerases.
DNA molecules isolated from bacteriophage P4 are mostly linear with cohesive ends capable of forming circular and concatemeric structures. In contrast, almost all DNA molecules isolated form P4 tailless capsids (heads) are monomeric DNA circles with their cohesive ends hydrogen-bonded. Different form simple DNA circles, such P4 head DNA circles contain topol
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6. A simple topological method for describing stereoisomers of DNA catenanes and knots.
Although linking number is an effective topological invariant for describing supercoiled DNA, it is inadequate for the additional interwinding in catenated or knotted DNA. We explain how the two-bridge theory of Schubert provides a powerful yet simple method for analyzing these forms by associating them with two integral invariants, alpha and beta, that meas
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7. Equilibrium distributions of topological states in circular DNA: Interplay of supercoiling and knotting
Two variables define the topological state of closed double-stranded DNA: the knot type, K, and ΔLk, the linking number difference from relaxed DNA. The equilibrium distribution of probabilities of these states, P(ΔLk, K), is related to two conditional distributions: P(ΔLk|K), the distribution of ΔLk for a particular K, and P(K|ΔLk) and also to two simp
The National Academy of Sciences.
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8. Electron microscopic studies of the different topological forms of the cauliflower mosaic virus DNA: knotted encapsidated DNA and nuclear minichromosome.
Cauliflower mosaic virus (CaMV) DNA exists under different topological forms in infected plants. First, the population of encapsidated CaMV DNA molecules appears heterogeneous when analysed by gel electrophoresis. The electron microscopic study reported here reveals that CaMV virion DNA contains simple and multiple topological knots. Second, a supercoiled DN
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9. Topoisomerase IV, alone, unknots DNA in E. coli
Knotted DNA has potentially devastating effects on cells. By using two site-specific recombination systems, we tied all biologically significant simple DNA knots in Escherichia coli. When topoisomerase IV activity was blocked, either with a drug or in a temperature-sensitive mutant, the knotted recombination intermediates accumulated whether or not gyrase wa
Cold Spring Harbor Laboratory Press.
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10. An RNA topoisomerase.
A synthetic strand of RNA has been designed so that it can adopt two different topological states (a circle and a trefoil knot) when ligated into a cyclic molecule. The RNA knot and circle have been characterized by their behavior in gel electrophoresis and sedimentation experiments. This system allows one to assay for the existence of an RNA topoisomerase,
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11. Gin-mediated DNA inversion: product structure and the mechanism of strand exchange.
Inversion of the G loop of bacteriophage Mu requires the phage-encoded Gin protein and a host factor. The topological changes in a supercoiled DNA substrate generated by the two purified proteins were analyzed. More than 99% of the inversion products were unknotted rings. This result excludes synapsis by way of a random collision of recombination sites, beca
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12. The Role of Topoisomerase II in Meiotic Chromosome Condensation and Segregation in Schizosaccharomyces pombe
Topoisomerase II is able to break and rejoin double-strand DNA. It controls the topological state and forms and resolves knots and catenanes. Not much is known about the relation between the chromosome segregation and condensation defects as found in yeast top2 mutants and the role of topoisomerase II in meiosis. We studied meiosis in a heat-sensitive top2 m
The American Society for Cell Biology.