W. D. Powrie

Isolation and characterization of cholesterol-5B,6B-oxide from an aerated aqueous dispersion of cholesterol

An unknown autoxidation product in an aerated cholesterol sol was isolated by preparative thin layer chromatography. This compound was identified as cholesterol-5β,6β-oxide by gas liquid chromatography along with infrared and mass spectrometry.

Gas hydrates in aqueous-organic systems. II. Concentration by gas hydrate formation.

Summary The ice-like nature of gas hydrates would appear to make them of potential value for concentrating aqueous fluids. The concentration process is similar to freeze concentration, but higher and possibly more economical operating temperatures could be used. Hydrates of CH3Br and CCl3F were utilized for concentrating apple, orange, and tomato juices. CCl3F was limited to 15 to 20% (v/v), since larger quantities resulted in solidification of the substrate, and smaller quantities lessened the concentration effect. No difficulty was encountered in removing approximately 80% of the water from the substrates. A basket-type centrifuge was used to separate the hydrate crystals from the fluid phase. The purity of the crystals was further improved by washing. The concentration process diminished the color and flavor of most substrates, and frequently imparted a slightly bitter aftertaste. Differences were noted in the suitability of substrates and hydrate formers for use in the concentration process.

Gas hydrates in aqueous-organic systems: I. Preliminary studies*†

Summary Gas hydrates are ice-like compounds, many of which are capable of existing at temperatures well above 0°C, providing the pressure is sufficient. They consist of small “guest” molecules, such as halogenated, short chain hydrocarbons, which are physically entrapped in hydrogen-bonded eages of HOH molecules (the “host”). This study involved hydrates of CH 3 Br and CCl 3 F. Stirring speed affected the rate of hydrate formation, but had no effect on the total amount formed. Gradual addition of the hydrate former failed to alter the rate or amount of hydrate formation as compared to the single addition method. Closed reaction vessels and low air temperatures were helpful in obtaining maximum hydrate formation. Increases in the volume per cent of the hydrate former resulted in greater amounts of hydrate and decreased efficiency (less hydrate per gram of hydrate former). It was possible to form gas hydrates in aqueous systems containing sizable quantities of carbohydrates, proteins, or lipids. Various solutes were found to depress hydrate decomposition temperature and freezing point to the same extent.

Effect of gas hydrates and hydrate formers on invertase activity

Abstract Gas hydrates are inclusion compounds of the clathrate or cage type, many of which are stable above 0 °. The object of this study was to determine the effects of some gas hydrates and hydrate formers on invertase activity. It was shown that invertase activity: (1) was not significantly influenced by the increase in solute concentration that accompanied hydrate formation, (2) was not significantly influenced by the presence of crystalline hydrates of CCl3F or propane, (3) was decreased significantly and irreversibly by exposure to liquid CCl3F, and (4) was decreased greatly and irreversibly by gradual decomposition of either CCl3F or propane hydrate. Since hydrate decomposition results in a molecular dispersion of the hydrate former in water, intimate contact would no doubt occur between the hydrate former (CCl3F or propane) and invertase, and this is the probable cause of the decrease in enzyme activity.

Steroids in bovine muscle and adipose tissue.

Thin layer and gas liquid chromatography, (GLC) were employed as complementary techniques to investigate naturally-occurring steroids in the unsaponifiable matter of bovine muscle and adipose tissue. Three GLC liquid phases, differing in selective partition properties, were used to effectively identify unknown steroids. The results indicate that cholesterol and minor amounts of desmosterol, Δ7-cholestenol, lanosterol, dihydrolanosterol, dehydromethostenol, Δ8-methostenol, Δ7-methostenol, cholestanol and possibly ergosterol were present in the bovine tissues. The minor steroids, with the exception of cholestanol and ergosterol, are steroid precursors in cholesterol biosynthesis. Common hormonal steroids were not found in the unsaponifiables of the tissues.

Gas hydrates in aqueous-organic systems: III. Hydrate formation in polyacrylamide gel*†

Summary The formation of gas hydrates in polyacrylamide gels was attempted using hydrate formers with different solubilities in water. Hydrate crystals of highly water-insoluble trichlorofluoromethane formed only at the gel-hydrate former interface. Hydrate crystals of highly water-soluble ethylene oxide formed abundantly within the gel, and the depth of penetration depended on the equilibration time prior to initiation of crystallization. Equilibration for 166 hrs resulted in the formation of ethylene oxide hydrate throughout a 5-cm column of gel. All ethylene oxide samples were observed to recrystallize following the initial crystallization process. Hydrate crystals of highly watersoluble sulfur dioxide and slightly soluble dichlorofluoromethane also formed within the gel. The sulfur dioxide hydrate crystals were present in quantities similar to those obtained with ethylene oxide, whereas the dichlorofluoromethane hydrate crystals were far less abundant. Several of the experiments were successfully repeated using an agar substrate. In the case of dichlorofluoromethane, the quantity of hydrate crystals in the gel was influenced by the method of formation. This was not true of ethylene oxide hydrate.

Rotation apparatus for shell-freezing

Summary A shell-freezing apparatus consisting of eight double-headed, clutch-activated, rotator stations was designed, constructed and successfully tested. Although the apparatus was designed to facilitate gas hydrate formation, other obvious applications include shell-freezing as a prelude to freeze-drying, and freezing and thawing at accurately controlled rates.

Stabilization of CCl3F hydrate by air or carbon dioxide

Summary The decomposition temperature of CCl 3 F hydrate can be increased from 8.6°C–18.3°C by the application of carbon dioxide as a help gas.

Apparatus for tranferring and freezing tissue under high pressure

Summary Certain physical effects of high pressure gases on tissue can be determined by conventional freeze-substitution methods, providing the operational pressure is maintained while the specimen is being frozen. An apparatus for accomplishing the transfer and freezing operations under pressure was constructed and has proven satisfactory.