RESUMEN

(-)-Centratherin is a bioactive sesquiterpenoid lactone, whose absolute configuration (AC) was not established, but has been proposed based on those of germacrane precursors. To verify this proposal, the experimental electronic circular dichroism (ECD), electronic dissymmetry factor (EDF), optical rotatory dispersion (ORD), vibrational circular dichroism (VCD), and vibrational dissymmetry factor (VDF) spectra of (-)-centratherin have been analyzed with the corresponding density functional theoretical predictions. These analyses suggest the AC of naturally occurring (-)-centratherin to be (6R,7R,8S,10R,2'Z).

Asunto(s)

RESUMEN

To determine the absolute configuration of 3-ishwarone, the experimental electronic circular dichroism (ECD), electronic dissymmetry factor (EDF), optical rotatory dispersion (ORD), vibrational circular dichroism (VCD), and vibrational dissymmetry factor (VDF) spectra of (+)-3-ishwarone are analyzed with the corresponding density functional theoretical predictions for different diastereomers. ECD and ORD spectra by themselves could not facilitate the determination of the absolute configuration of this molecule. However, the magnitude of the experimental EDF of (+)-3-ishwarone is found to match better with that predicted for the (1R,2S,4S,5R,9R,11R) diastereomer. The analyses of similarity measures between experimental and predicted spectra for VCD and VDF clearly suggested that the absolute configuration of (+)-3-ishwarone is (1R,2S,4S,5R,9R,11R).

Asunto(s)

RESUMEN

O objetivo deste estudo foi comparar ex vivo a capacidade de manutenção do eixo central do canal após a instrumentação com dois sistemas rotatórios de n¡quel titânio: sistema ProTaper Universal© e sistema EndoWave©. Para tanto, foram utilizados para o estudo 20 raízes mesiais de molares inferiores que possuíam canais mesiais separados em todo o eixo longitudinal que foi avaliado antes e depois da instrumentação, usando-se a metodologia de avaliação de imagens transversais das raízes pré e pós-instrumentação proposta por Bramante4 (1987) e modificada por Kuttler14 (2001). Foram realizados os acessos, e os comprimentos de trabalho (CT) foram padronizados em 18.00 mm. As amostras foram incluídas em resina acrílica dentro da mufla. Os dentes foram seccionados a 3, 6 e 9 milímetros do  pice radicular e imagens pré-instrumentação foram obtidas dos cortes transversais através de método fotográfico. As amostras foram remontadas no cubo endodôntico e posteriormente 20 canais foram preparados com o sistema ProTaper Universal© e 20 canais foram preparados com o sistema EndoWave©. Foram realizadas novas imagens pós-instrumentação, que foram sobrepostas e avaliadas por meio do programa AutoCad© para determinar o desvio do eixo central do canal após o preparo endodêntico. Os dados obtidos foram submetidos … análise estatística, através do teste Two-Way ANOVA. O nível de significância foi de 5%. Os canais vestibulares e linguais das seções a 3, 6 e 9 mm do  pice mostraram um leve desvio do eixo central do canal após a instrumentação (0.109 mm para o sistema Protaper Universal© e 0.112 mm para o sistema EndoWave©), porém não houve diferenças estatisticamente significativas no desvio entre os dois sistemas em nenhum nível da raiz. Desta forma, a instrumentação com qualquer um dos dois sistemas pesquisados propiciou a manutenção do eixo central dos canais sem alterações significativas.

The aim of this study was to compare ex vivo the ability to preserve the central axis of a canal after instrumentation with two nickel-titanium rotary systems: ProTaper Universal© and EndoWave©. Twenty mesial roots of mandibular molars with separated mesial roots all along the longitudinal axis were assessed before and after instrumentation using a cross-sectional image assessment methodology for pre and post-instrumentation roots, as proposed by Bramante4 (1987) and modified by Kuttler14 (2001). Accesses were performed, the working length (WL) was standardized to 18.00 mm, and samples were embedded in acrylic resin inside a muffle. The teeth were cut at 3, 6, and 9 mm from the apex and pre-instrumentation images were obtained from cross sections through a photographic method. Samples were reassembled in the endodontic cube and subsequently prepared; 20 canals were prepared with the ProTaper Universal© system, and 20 canals were prepared with the EndoWave© system. New images were taken after instrumentation, which were overlapped and evaluated with AutoCad©, a computer graphics program to determine the deviation from the central axis of the canal after endodontic preparation. Data gathered underwent statistical analysis through the Two-Way ANOVA test. The significance level was 5%. Buccal and lingual canals for those sections at 3, 6, and 9 mm from the apex showed a slight deviation from the central axis of the canal after instrumentation (0.109 mm for the ProTaper Universal© and 0.112 mm for the EndoWave©), but there was no statistically significant differences in deviation between the two systems at any level of the root. Thus, instrumentation with any of the two systems under investigation provided for preservation of the central axis of the canals with no significant changes

Asunto(s)

RESUMEN

This report deals with on optical rotatory dispersion and viscosity study of hyaluronic acid with the electric organ of Electrophorus electricus (L.). This acidic polysaccharide exhibits an intrinsic Cotton effect (negative) around 212 nm in aqueous solutions. Extrinsic Cotton effects are developed by its interaction with cationic dyes which is an indication of ordered conformation in solution involving the polymer anionic sites. Viscosity measurements showed that hyaluronic acid behaves, in solution, as a polyelectrolyte with a decrease in intrinsic viscosity in media of high ionic strength and of low dielectric constant. With the quaternary ammonium compounds acetylcholine and gallamine triethyliodide, this polyelectrolyte also displays an interaction which affects both its optical rotatory dispersion and viscosity properties which is indicative of a conformational change.

Asunto(s)

Asunto(s)