Planarity
Mostrando 13-24 de 34 artigos, teses e dissertações.
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13. La modelización molecular como herramienta para el diseño de nuevos polímeros conductores
The ability of molecular modeling techniques based on quantum chemical methods to predict the molecular and electronic structure of organic conducting polymers is examined. More specifically, we report on the applicability of these computational tools to study different aspects of polythiophene and its derivatives: molecular geometry and planarity, the struc
Polímeros. Publicado em: 2005-11
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14. SÍNTESE, ESTRUTURAS DE TRIAZENO 1-ÓXIDO E COMPLEXO DE K+, E AVALIAÇÃO DA ATIVIDADE BIOLÓGICA DE 1-METILTRIAZENOS 1-ÓXIDO E 1,3-BIS(ARIL)TRIAZENOS / SYNTHESIS, STRUCTURE OF TRIAZENE 1-OXIDE AND COMPLEX OF K+, AND EVALUTION OF BIOLOGICAL ACTIVITY OF 1-METILTRIAZENES 1-OXIDE AND 1,3-BIS(ARIL)TRIAZENES
This work is associated with the crystal and molecular structure analysis of two free triazene 1-oxide molecules and a complex with K+ involving a p-carboxyfenil-substituted single protonated triazene 1-oxide ligand. 1-metil-3-(p-carboxyphenyl)triazene 1-oxide (1) crystallizes in the monoclinic system, space group C2/c, with cell parameters a = 27.2046(8) Å
Publicado em: 2005
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15. AplicaÃÃo de mÃtodos correlacionados de estrutura eletrÃnica ao estudo de estados excitados de molÃculas em fase gasosa e em soluÃÃo
Ab-initio electronic structure calculations, at correlated level, are applied to the study of excited states of molecules in gas-phase and solution. The electron correlated methods comprise the multiconfigurational SCF (MCSCF), and the multi-reference CI method with single and double excitations (MR-CISD), which is used in combination with MCSCF, then provid
Publicado em: 2005
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16. "Não linearidades ópticas em azocompostos" / Optical nonlinearities in azocompounds
This work reports on the temperature dependence of linear and nonlinear properties of azocompounds solutions due to isomerization mechanisms. The dependence of pipi* transitions on the linear structure of azocompounds is already noticeble in the measurements of absorption spectra as function of the temperature for the trans isomer. Knowing the energy levels
Publicado em: 2004
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17. Estudo da estabilidade conformacional do copolimero poliazina-policarbonitrila
The trans-polycarbonitrile polymer presents a strong deviation from the planarity suggesting that this conformation does not correspond to the most stable structure of the system. These non-planarity can affect significantly the electronic properties of the polymer. On the other hand the polyazine derivative, a conjugated polymer, a nitrogen containing analo
Publicado em: 1999
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18. Differential behavior of curved DNA upon untwisting
We have synthesized DNA segments with different handedness, twisting and radii of curvature, and have analyzed the effect of untwisting on them. The results indicate that the dynamic behavior of curved DNA upon untwisting is strongly determined by the initial sequence-dependent DNA trajectory. In particular, DNA with the same radii but with opposite handedne
The National Academy of Sciences of the USA.
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19. Structure-related inhibitory effect of antimicrobial enoxacin and derivatives on theophylline metabolism by rat liver microsomes.
Enoxacin, an antimicrobial fluoroquinolone with a 7-piperazinyl-1, 8-naphthyridine skeleton, is a potent inhibitor of cytochrome P-450-mediated theophylline metabolism. The present study was designed to clarify, using seven enoxacin derivatives, the molecular characteristics of the fluoroquinolone responsible for the inhibition. Three derivatives with methyl
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20. Interaction of DAPI with double-stranded ribonucleic acids.
The interaction of DAPI with natural and synthetic double-stranded polyribonucleotides was studied with different optical and calorimetric methods. The results were similar to those obtained previously with double-stranded polydeoxynucleotides, i.e. two interaction modes, the first of which shows high affinity for AU clusters and consequent strong fluorescen
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21. Refined crystal structure of the molecular complex of Streptomyces griseus protease B, a serine protease, with the third domain of the ovomucoid inhibitor from turkey.
We have determined the crystal structure of the molecular complex between Streptomyces griseus protease B (SGPB), a bacterial serine protease, and the third domain of the ovomucoid inhibitor from turkey. Restrained-parameter least-squares refinement of the structure with the 1.8-A intensity data set has resulted in an R factor of 0.125. The carbonyl carbon a
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22. Temperature and salt dependence of the gel migration anomaly of curved DNA fragments.
A series of oligonucleotides of different sequences have been cloned to study DNA curvature. Several DNA fragments containing these oligonucleotides in various numbers of repeats were analyzed in 10% polyacrylamide gels. A strong gel migration anomaly was found for dA4 sequences; a comparably very small but clearly detectable anomaly was observed for dA3 (bo
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23. A molecular mechanical study of complexes formed between 4-nitroquinoline-N-oxide and dinucleoside phosphates.
Molecular mechanical calculations were done on complexes of 4-nitroquinoline-N-oxide (NQO) with various dinucleoside phosphates [(ApT)2, (CpG)2, (GpC)2, and (TpA)2]. Models built using proflavine (uniform C3' endo sugar puckers) and acridine orange (mixed C3' endo (3'-5') C2' endo sugar puckers) dinucleoside phosphate X-ray structures were used in the calcul
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24. Intercalative and nonintercalative binding of large cationic porphyrin ligands to calf thymus DNA.
The large meso-substituted porphine, meso-tetra(4-N-methylpyridyl)porphine has been identified as a DNA-interactive ligand with a capacity for intercalation (1,2). Subsequently, the 2-N-methyl, 3-N-methyl and N-trimethylanilinium analogues of this porphyrin intercalator have been obtained for physico-chemical analyses (absorption spectroscopy, viscometry, ci