Direct in situ observation of the fine structure of the cationic lipid monolayer−DNA complex on a water surface has been carried out by using an air−water interface X-ray reflectivity (XR) instrument. Interestingly, the thickness of the DNA layer was markedly thinner than the geometry of the cylindrical DNA molecule when the complex was deposited on the solid substrates; the thickness was determined to be 11 Å by XR measurement in a dried state, while the diameter of the DNA molecule is about 24 Å. However, the thickness in the complex on a water surface was estimated by in situ XR measurement to be about 25−28 Å, which is comparable to the geometry of the DNA molecule. Thus, the anomalously thin thickness was due to some experimental treatments, such as deposition on a solid substrate and/or drying. The structure of the monolayer and monolayer−polymer complex on the solid substrates in a dried state is not the same as that on a water surface. The possibility of some dynamic fluctuation of its structure was also suggested. These results strongly indicate the importance of a direct in situ study such as by the XR technique for the structural study of the monolayer and monolayer complex on a water surface.

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Concentrations of anthropogenic radionuclides were measured in the muscle of marine mammals collected from various locations all over the world, and the global distribution of 137Cs in marine mammals was investigated. 40K was detected in all the specimens of marine mammals with no apparent difference between regions. An anthropogenic radionuclide, 137Cs, was detected in most of the species of marine mammals. With regard to the worldwide distribution of 137Cs, the highest concentration was noticed in the U.K. coast, followed by Lake Baikal, and decreases toward the southern sampling points. A strong positive correlation was observed between 137Cs levels in the muscle of marine mammals and the ambient seawater. Marine mammals feeding on fishes showed a higher concentration factor (CF) for 137Cs than those feeding on cephalopods. To our knowledge, this is the first report on the global distribution of 137Cs and the effect of feeding habits on the CF values of 137Cs in marine mammals.

X-ray reflectometry (XR) was carried out on amphiphilic diblock copolymer poly(α-methylstyrene)-block-poly(decyl 4-vinylpyridine) monolayers on a water surface and on a glass plate. From XR data, the layer thickness and surface and interface roughness were determined. For comparison, atomic force microscopy (AFM) was carried out on the samples deposited on solid substrates (glass and mica). From XR data, it was quantitatively clarified that the monolayer became thicker and rougher by the deposition on solid substrates than on the water surface. AFM revealed aggregates formed on the solid substrates. The structural difference between the samples on a water surface and on solid substrates may be due to the preparation procedure of the sample on solid substrates. These findings indicate that the correct and precise information for the structure of the monolayer on water surface can be evaluated only by in situ experiments such as XR.