The active species of "CO(2)" and the amount of fractionation of stable carbon isotopes have been determined for a partially purified preparation of phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31) from corn (Zea mays) leaves. The rates of the enzyme reactions, using substrate amounts of HCO(3) (-), CO(2) or CO(2) plus carbonic anhydrase, show that HCO(3) (-) is the active species of "CO(2)"...

Understanding the coupling of oxygen, carbon, and sulfur cycles in the past is critical for reconstructing the history of biogeochemical cycles, paleoclimatic variations, and oceanic chemistry. The abundance of sulfur isotopes (dS) in sulfate from ancient marine carbonates, or carbonate-associated sulfate (CAS), is commonly used, along with other archives (mainly evaporites and barite), to esti...

Ignorance of the location or inaccessible locations of lifestages can impede the study and management of species. We used stable isotopes of carbon and nitrogen to identify the habitats and diets and to estimate the duration of a 'missing' lifestage: the early juvenile stage of the green turtle, Chelonia mydas. Stable isotopes in scute from young herbivorous green turtles in shallow-water habit...

water use efficiency (wue, the ratio of total dry matter to water use) became a breeding target only when it was found that carbon stable isotopes were inversely related to wue. the current study conducted under well-watered and drought conditions in the field over two years at broom’s barn research station, uk, was undertaken to investigate the extent of genotypic differences for water use, yi...

The analysis of hydrogen stable isotopes (δD) is a potentially powerful tool for studying animal ecology. Unlike other stable isotopes used in ecological research, however, we are less familiar with the physiological processes that influence the incorporation of hydrogen isotopes from dietary resources to animal tissues. Here we present the results of a controlled feeding experiment utilizing J...

Introduction: Sulfur is a cosmochemically important element with four stable isotopes. It is the only element besides oxygen where a mass independent fractionation (MIF) has been observed both in nature [1-4] and the laboratory [4,5]. Unlike oxygen, where more than one process can produce MIF, sulfur MIF is exclusively of photochemical origin. Recently we have demonstrated a mass independent su...