PubMed · 5025938
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J H McAlear, R Fucci, L Germinario. 1972. A simple cold stage for the scanning electron microscope.. https://doi.org/10.1016/0014-4827(72)90285-6
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In this investigation, the structure and behaviour of frozen solutions of human serum albumin (HSA) alone and in combination with the cryoprotectant polyvinylpyrrolidone (PVP) have been studied using low frequency dielectric analysis and modulated temperature differential scanning calorimetry (MTDSC). Solutions of HSA (1-10 w/v%) and combined solutions (from 1 to 5 w/v% of each ingredient) were prepared and studied thermally and dielectrically over a frequency range of 10(5)-10(-2)Hz every 10 degrees C from +20 to -70 degrees C. Dielectric data were fitted according to the Dissado-Hill theory and the relaxation times calculated. In addition, a relaxation peak was noted for the frozen HSA systems at a frequency approximately one order of magnitude lower than that seen for the PVP systems, with the PVP dominating the response of the mixed systems. The systems showed Arrhenius behaviour, with, for example, the 5% HSA solution showing an activation energy for the relaxation process of 19.34 kJ/mol. In accordance with previous studies on frozen aqueous solutions of PVP, the results suggest that unfrozen water dominated the dielectric response, with the local environment surrounding the HSA being strongly influenced by the PVP. MTDSC data indicated that the PVP and HSA interact in a complex manner in solution, with a glass transition attributable to PVP being seen only in those systems where PVP was present in sufficient excess. In conclusion, the study has suggested that MTDSC and dielectric spectroscopy may be the useful complementary tools with which the structure and molecular mobility of frozen proteinaceous systems may be studied.
A 1H and 13C NMR study on the inclusion complex of paroxetine with beta-cyclodextrin was carried out in order to define the stoichiometry of the association and its strength. Proton and carbon chemical shift measurements of paroxetine and beta-cyclodextrin were performed at several molar ratios and temperatures, allowing the determination of a 1:1 stoichiometry and an association constant value of the order of 2 x 10(3) for the paroxetine-beta-cyclodextrin complex. Overhauser effects in the rotating frame were also measured, and the experimental interproton distance constraints have been used for molecular model building of the complex. The obtained model indicates that the benzodioxolyl moiety of paroxetine is deeply inserted in the cavity of the cylindrical structure of beta-cyclodextrin, while the fluoro-phenyl ring lays above the wider rim.
The spray freezing process, a natural freezing technology, was used to treat pulp mill effluent and oil sands tailings pond water. The wastewaters froze partially or completely (i.e. with or without runoff generation) during the spraying operation. Greater than 60% impurity reduction in the spray ice was obtained when 30% of the total volume of the sprayed water was released as runoff. Organic and inorganic contaminants were rejected with different efficiencies. The impurities were uniformly distributed within the ice columns when the spray ice was produced without generating any runoff. While a significant increase in impurity concentration was observed at the bottom of the ice formed with runoff production. The spray freezing process is an effective and economically feasible technique for wastewater treatment in cold regions. To achieve higher impurity removal efficiency, the wastewater should be only partially frozen during spray ice production.