Identificación de biomarcadores saturados en un carbón bituminoso tratado con ácido y un solvente no convencional / Identification of biomarkers in a bituminous coal treated with acid and an unconventional solvent / Identificação de biomarcadores saturados em carvão betuminoso tratado com ácido e solvente não convencional

Resumen Este artículo describe los biomarcadores saturados (n־alcanos, hopanos y esteranos) identificados en los extractos obtenidos de un carbón bituminoso, tratado con ácido y un solvente no convencional. Los extractos de carbones bituminosos venezolanos se obtuvieron a través de cloroformo (solvente convencional) y N,N־dimetilformamida ־DMF־ como solvente de alto poder extractivo, con y sin tratamiento ácido previo, con el fin de evaluar el rendimiento y distribución de biomarcadores característicos. El rendimiento de extracción con DMF alcanzó 44% p/p, mientras que con CHCl3, este valor no superó el 2% p/p. La desmineralización previa con HCl incrementó el rendimiento de extracción sin afectar la distribución de los biomarcadores, salvo en la relación de hidrocarburos ligeros respecto a los pesados. Se propone DMF como solvente de elección para obtener información geoquímica en carbones meteorizados.

Abstract This article describes saturated biomarkers (n־alkanes, hopanes and steranes) identified in the extracts obtained from a bituminous coal treated with acid and an unconventional solvent. Extracts of Venezuelan bituminous coals were obtained through chloroform (conventional solvent) and N,N־ dimethylformamide ־DMF־ as high extractive solvent, with and without previous acid treatment, to evaluate the performance and distribution of characteristic biomarkers. The extraction yield with DMF reached 44% w/w, while with CHCl3, this value did not exceed 2% w/w. Previous demineralization with HCl increased the extraction yield without affecting the distribution of the biomarkers, except in the ratio of light hydrocarbons to the heavy ones. DMF, therefore, is proposed as the solvent of choice to obtain geochemical information on weathered carbons.

Resumo Este artigo de pesquisa descreve os biomarcadores saturados identificados (n־alcanos, hopanos y esteranos) em extratos obtidos a partir de carvão betuminoso, tratado com ácido e um solvente não convencional. Extratos de carvão betuminoso venezuelano foram obtidos utilizando־se clorofórmio (solvente convencional) e N,N־ dimetilformamida ־DMF־ como solvente extrativo elevado, com e sem tratamento ácido prévio, com o objectivo de avaliar o rendimento e distribuição de biomarcadores característicos. O rendimento de extração com DMF atingiu 44% p/p; com CHCl3 o valor não excedeu 2% p/p. A desmineralização prévia com HCl aumentou o rendimento da extração sem afetar a distribuição dos biomarcadores, exceto na proporção de hidrocarbonetos leves e pesados. DMF é proposto como o solvente de eleição para obter informações geoquímicas sobre os carvões intemperizados.

Fourier-transformed infrared spectroscopy: a tool to identify gross chemical changes from healthy to yellow band disease tissues.

Yellow band disease (YBD) is a common and wide-spread Caribbean syndrome that affects the genus Orbicella, a group of species that constitute the framework of Caribbean coral reefs. Previous studies have shown that the structure and function of bacterial assemblages vary between healthy tissues and YBD lesions; however, how the molecular composition of tissues varies as tissues transition from healthy to YBD has not been determined before. The present study provides the first survey of macromolecules found from healthy (H), apparently healthy (AH), transition (TR) and YBD tissues of Orbicella faveolata. For this, we used Fourier-transformed mid-infrared spectroscopy (FTIR) to compare absorption profiles as a proxy for the gross molecular composition of decalcified H, AH and YBD tissues. We found a significantly higher level of infrared absorption for bands assigned to lipids in H tissues compared to YBD tissues, suggesting that lipid compounds are more abundant in compromised tissues in relation to other macromolecules. We also found a lower level of intensity of bands assigned to carbohydrates and proteins in YBD tissues, compared to H and AH tissues. A similar pattern was observed for phospholipidic compounds in relation to fatty acids. This study is the first to show that healthy and YBD-compromised tissues have different infrared absorption profiles, suggesting that alterations in the biochemical composition occur during pathogenesis. Future studies should focus on determining the actual concentration of these compounds in H, AH, TR and YBD tissues and on testing the role of translocation of photoassimilates from H tissues and/or from endolithic algae to YBD tissues.

Characterization of Xenorhabdus and Photorhabdus bacteria by Fourier transform mid-infrared spectroscopy with attenuated total reflection (FT-IR/ATR).

The use of Fourier transform mid-infrared spectroscopy with attenuated total reflection for characterizing entomopathogenic bacteria from genera Xenorhabdus and Photorhabdus is evaluated for the first time. The resulting spectra of Xenorhabdus poinarii and Photorhabdus luminiscens were compared with the spectrum of Escherichia coli samples. The absorption spectra generated by the bacteria samples, were very different at the region below 1400cm(-1) which represents the stretching vibrations of phosphate and carbohydrates. Star diagrams of the fingerprint section of nematodes spectra (between 1,350 and 1,650 cm(-1)) for separation between spectra was used and showed to be a useful tool for classification purposes.