Ammonium acetate, electron microscopy

Electron microscopy and X-ray microanalytical methods showed that uranium as uranyl nitrate hexahydrate penetrated the stratum corneum within 15 minutes and accumulated in the intracellular space between the viable epidermis and the stratum corneum (De Rey et al. 1983). As is the case with inhalation and oral absorption, water solubility is an important determinant of absorption, and no penetration was observed with the insoluble compounds uranium dioxide, uranyl acetate, or ammonium diuranate. After 48 hours, uranium applied as uranyl nitrate was no longer found in the skin and toxicity developed, indicating that the uranium had been absorbed into the blood. 

Microscopy techniques may also be used to perform size estimations and to corroborate the size homogeneity in a population. Transmission electronic microscopy (TEM), scanning electronic microscopy (SEM) and atomic force microscopy (AFM) are the most used. Nevertheless, these techniques are more often applied for visual characterization of size and distribution in order to corroborate data obtained with other techniques. This is because the theory behind most of the techniques used for size determination relies on the use of monodisperse and spherical particles. Any deviation from this condition may give unrealistic results that consequently may affect the efficacy of the system. In TEM measurements, a contrast agent is normally necessary for proper visualization, such as uranyl acetate, osmium tetroxide, ammonium molybdate or phosphotungstic acid. Because of its high resolution, AFM can also be useful to detect interactions between plasmids and nanostructures [77]. 

Fig. IX-4. An electron micrograph of reconstituted DNA-clupeine complexes. The complexes, formed by the slow-binding method from native herring sperm DNA and whole clupeine, were dissolved in 4 M ammonium acetate. Samples for electron microscopy were prepared according to the method of Kleinschmidt et al. (1962) and shadow-casted with platinum-palladium (80 20, v/v) (from Inoue and Fuke, 1970)... 

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