The carbon atoms of glucose and malate in C(4) plants are 2 to 3 per thousand enriched in (12)C with respect to atmospheric CO(2); whereas these intermediates in C(3) plants are 15 to 18 per thousand enriched with (12)C with respect to atmospheric CO(2). The enzymatic synthesis of malate from phosphoenolpyruvate and bicarbonate in preparations of leaves of Sorghum bicolor, Haygrazer result in a...

Stable isotope geochemistry is a branch of geology that investigates the age of natural materials, their origin and the processes they have undergone since formation [1]. Stable isotope analysis is also used in biogeochemical studies to monitor element cycling in ecosystems [2] and to identify geographical/regional differences for food provenance and archaeology. Of the elements of interest in ...

Oxygen and carbon isotopic compositions of ambient carbon dioxide in two tropical forests in the Amazonian basin were determined at the beginning and the end of the dry season. One site, Fazenda Vitoria, is typical of a seasonal forest with a pronounced dry season from May to November whereas the other site, Reserva Ducke, has a milder dry season. Samples collected at night revealed that in the...

Marine dissolved organic carbon (DOC) is a large (660 Pg C) reactive carbon reservoir that mediates the oceanic microbial food web and interacts with climate on both short and long timescales. Carbon isotopic content provides information on the DOC source via δ(13)C and age via Δ(14)C. Bulk isotope measurements suggest a microbially sourced DOC reservoir with two distinct components of differin...

Kinetic isotope effects (KIEs) during the inorganic hydration of carbon dioxide (CO2) in aqueous solution cause reduced stable carbon and oxygen isotope ratios (C=C and O=O) in the reaction product carbonic acid (H2CO3) or bicarbonate ion (HCO 3 ), relative to CO2. While such KIEs are of importance in various physicochemical, geochemical, and biological systems, very few experimental and theore...

A method has been developed for the positional 13C isotope analysis of pyruvate and acetate by stepwise quantitative degradation. On its base, the kinetic isotope effects on the pyruvate dehydrogenase reaction (enzymes from Escherichia coli and Saccharomyces cerevisiae) for both of the carbon atoms involved in the bond scission (double isotope effect determination) and on C-3 of pyruvate have b...

Fractionation of stable carbon isotopes upon degradation of trichlorobenzenes was studied under aerobic and anaerobic conditions. Mineralization of 1,2,4-trichlorobenzene by the aerobic strain Pseudomonas sp. P51 which uses a dioxygenase for the initial enzymatic reaction was not accompanied by a significant isotope fractionation. In contrast, reductive dehalogenation by the anaerobic strain De...

Leaves of 10 randomly selected plants representing eight dicotyledonous families were exposed to (14)CO(2) for a 10-minute period in the light. Citrate and alanine were isolated, purified isotopically, and degraded to obtain the (14)C-isotope distribution of corresponding carbon atoms, i.e. citrate (C-1,2) and alanine (C-2,3). The cited carbon atoms of alanine were equally labeled as is typical...

The carbon-isotope ratio recently obtained for the carbon found in the Murchison meteorite, which has been shown (by the racemic nature of twelve component amino acids) to be free of terrestrial contamination, agrees with that for average terrestrial sediments. This finding indicates that the earth and the stony meteorites contain carbon of the same isotopic composition.

Soil is an integral part of terrestrial ecosystems. Many soil ecologists interested in soil ecosystem functioning rely, to some degree, on stable isotope methodologies. The study of the natural abundance of carbon isotopes, especially (13)C but also (14)C, in the environment and the use of stable carbon isotope tracers have proved very useful in investigating the soil carbon cycle and soil trop...