RESUMEN
The adsorption of adenosine 5'-monophosphate (5'-AMP) onto pyrite (FeS2) and its modulation by acetate, an organic precursor of complex metabolic pathways, was studied in aqueous media that simulate primitive environments. 5'-AMP adsorption requires divalent cations, indicating that a cationic bridge mediates its attachment to negatively charged sites of the mineral surface. The isotherm of 5'-AMP adsorption exhibits a strong cooperative effect at low nucleotide concentrations in acetate-rich medium, whereas high levels of adsorption were only found at high nucleotide concentrations in a model of primitive seawater (acetate free). The modulating role of acetate is also evidenced in the presence of high dipolar moment molecules: dimethyl sulfoxide (Me2SO) and dimethyl formamide (DMF) strongly inhibit 5'-AMP adsorption in acetate-rich media, whereas no effect of DMF was found in artificial seawater. The observation that exogenous divalent cations are not needed for acetate attachment onto FeS2 reveals that organic acids can interact with the Fe2+ atoms in the mineral surface. All considered, the results show that complex and flexible ironsulfide/biomonomers interactions can be modulated by molecules that accumulate in the interface layer.
Asunto(s)
Adenosina Monofosfato/química , Hierro/química , Sulfuros/química , Acetatos/química , Adsorción , Cationes , Dimetilsulfóxido/química , Dimetilformamida/química , Relación Dosis-Respuesta a Droga , Electroforesis , Concentración de Iones de Hidrógeno , Proteínas Hierro-Azufre/química , Agua de Mar/química , Factores de TiempoRESUMEN
This presentation is the result of the survey of eight industries with asbestosis risk in the Barcelona area (two of fibro-cement, three of auto brakes, two of textiles, and one of insulation materials). Of 1,472 workers, 271 or 18.5% have asbestosis. Pleural involvement in asbestosis is twice as common as that of the lung, 15.7% versus 8.5%. Pulmonary asbestosis without pleural participation is seen in only 2.6% of cases. Pleural plaques, calcified and not calcified, are detected in only a few cases. There is a definite correlation between the incidence of asbestosis and the exposure time: from 1% in the group of workers with less than five years of exposure up to 64.58% for those with 30 or more years of exposure. Clinical symptoms (cough, and/or expectoration, and/or dyspnea) were present in 68% of the studied population. Pulmonary crepitations are the most significant physical sign detected, observed in one quarter to one third of the patients. Pulmonary function tests in asbestos workers revealed restrictive and mixed type syndromes in 17% of the cases and obstructive syndrome in 36%. The percentages for those workers without asbestosis are 9% and 16%, respectively. It seems, therefore, that a bronchial factor plays a role in asbestosis. The bronchial pathology would be manifested clinically by the appearance or the exaggeration of the chronic bronchitis symptoms, and physiologically by the presence of the obstructive syndrome. There is no doubt that smoking enhances the incidence of asbestosis, aggravates the respiratory symptoms in those affected, and is a cause of further deterioration of pulmonary function.