Heavy-oxygen Water Research Articles

Isotopically heavy oxygen-containing siderite derived from the decomposition of methane hydrate

Authigenic siderite from the Miocene and Pliocene sediments of the Blake Outer Ridge formed in a methane fermentation zone in equilibrium with anomalously heavy oxygen water, as evidenced by its heavy-carbon (-1.6‰ to +12.5‰ δ13C) and heavy-oxygen (+0.1‰ to +7.9‰ δ18O) values. Blake Outer Ridge sediments are impregnated with methane hydrate, which is generally enriched in 18O relative to ambient water. This suggests that decomposition of methane hydrate and subsequent release of large amounts of methane and heavy oxygen water affected the formation of the 18O-enriched siderite. Gas hydrate reaction in sediments is an important process for causing a dramatic variation of oxygen isotopic composition of the interstitial water and of authigenic carbonates formed during burial diagenesis.

Studies on the mechanisms of action of proteolytic enzymes using heavy oxygen exchange.

Transpeptidation reactions catalyzed by chymotrypsin, pepsin, leucine aminopeptidase and thermolysin have been studied in heavy oxygen water (H2 18O). The 18O incorporation into the peptide bond of transpeptidation products and into the non-hydrolyzed substrate has been measured. The rates of 18O exchange in the carboxylic groups of N-acetylphenylalanine and leucine, catalyzed by pepsin and leucine aminopeptidase, respectively, have also been determined. These rates have been compared with that of the exchange in the presence of amino compounds which reversibly form amide bonds with the above carboxyl-containing substances. The data obtained show that, in contrast to chymotrypsin, other enzymes studied do not form 'acyl-enzymes' but function by the mechanism of general-base catalysis. In other words, their catalytically active groups promote the abstraction of a proton from the water molecule, which attacks the susceptible bond of the substrate. The structure of intermediate compounds in this type of catalysis and the mechanism of the transpeptidation reaction are discussed.

Thermal conductivity of heavy-oxygen water H2O18

The ratio of thermal conductivity coefficients of heavy-oxygen water H2O18 with different percentages of enrichment to the thermal conductivity coefficient of ordinary water is measured in the range of 0–40°C. Differences in the thermal conductivities and the temperature coefficients of the thermal conductivity of heavy-hydrogen water D2O and and heavy-oxygen water H2O18 are indicated.

Physical properties of heavy-oxygen water. Absolute viscosity of H218O between 15 and 35°C

The absolute viscosity of highly enriched heavy-oxygen water, H218O, has been measured at 5°C intervals between 15 and 35°C, using a semi-automatic closed viscometer of the suspended-level type. A linear extrapolation was performed to determine the viscosity of 100 % heavy-oxygen water, based upon the measured viscosity of natural water and that of a highly enriched heavy-oxygen water sample. The effect of isotope substitution on the viscosity of natural water has been analyzed for both H218O and D216O. The viscosity ratio at 25°C for H218O/H216O is 1.0536, whereas that for D216O/H216O is 1.2316.

Physical properties of heavy-oxygen water. Part 2.—Vapour pressure

A method has been developed for measuring small differences between the vapour pressures of two samples. V.p. differences were determined between water samples with a high concentration of oxygen-18 (H2O18 and D2O18) and samples with a low concentration in the temperature range 15–90°C. Differences between the vapour pressures of water containing ∼55 % O17 and samples containing high concentrations of O16 and O18 respectively, in the range 40–90°C, have also been measured. Using these results, vapour pressure ratios between the pure isotopic species were calculated.

Physical properties of heavy oxygen water. Part 1.—Density and thermal expansion

Physical properties of heavy oxygen water. Part 1.—Density and thermal expansion

Catalysis in the Exchanges of Organic Compounds with Heavy Oxygen Water

Catalysis in the Exchanges of Organic Compounds with Heavy Oxygen Water

Rare Heavy Oxygen Water Made by British-German Team

Rare Heavy Oxygen Water Made by British-German Team