The aim of this study was to investigate the possible existence and magnitude of stable carbon isotope discrimination by human 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR). The catalytic portion of HMGR was expressed and purified. The reaction product mevalonate was lactonized and extracted from the reaction mixture by a solid-phase extraction protocol. Stable carbon isotope ratios of...

This thesis investigated carbon and nitrogen dynamics of soil dwelling Collembola by using direct measurements and stable isotope additions. In an isotope change experiment, collembolans exchanged between 6 and 10 % of carbon and nitrogen in their body tissue per day to metabolism and between 0.5 and 2 % to reproduction. When collembolans on low and high protein diets were compared, animals on ...

The observation of one-dimensional N₂ inside single-walled carbon nanotubes raises the questions, how are the N₂ molecules formed and how do they manage to make their way to this peculiar place? We have used N(15) and C(13) isotope labeled acetonitrile during the synthesis of single-walled carbon nanotubes to investigate this process. The isotope shifts of phonons and vibrons are observed by Ra...

The stable isotope ratios of a seized pathogen culture could potentially reveal information about the environment in which the agent was produced. In this paper we describe general relationships between stable isotopes of carbon, nitrogen, and hydrogen in bacteriological culture media and spores of Bacillus subtilis, an endospore-forming soil bacterium. In numerous media that varied both in nut...

The ratio of carbon accumulation to transpiration, W, of wheat (Triticum aestivum L.) seedlings increased with increasing soil strength, measured as soil penetrometer resistance, and this was already apparent at the two leaf stage. The ratio was negatively correlated with carbon isotope discrimination, in accord with theory. This means that decrease in intercellular partial pressure of CO(2) ac...

Meyers, P.A., 1992. Changes in organic carbon stable isotope ratios across the K/T boundary: global or local control? In: S.A. Macko and M.H. Engel (Guest-Editors), Isotope Fractionations in Organic Matter: Biosynthetic and Diagenetic Processes. Chem. Geol. (Isot. Geosci. Sect. ), l 01: 283-29 I. A global shift in carbonate carbon j~3C-values from heavier values in the Maastrichtian to lighter ...

C-13 isotope fractionation in the decarboxylation of phenylpropiolic acid (PPA) in the 10% solution of diphosphoric acid (H4P2O7) in orthophosphoric acid (H3PO4) and in the solution of diphosphoric acid in metaphosphoric acid (HPO3) has been studied between 20–140 C (293.16–413.16). The initial C fractionation observed in the decarboxylation of PPA in 10% solution of H4P2O7 in H3PO4 in the temp...

Combustion-based studies of the carbon-13 content of plants give only an integrated, long-term value for the isotope fractionation associated with photosynthesis. A method is described here which permits determination of this isotope fractionation in 2 to 3 hours. To accomplish this, the plant is enclosed in a glass chamber, and the quantity and isotopic content of the CO(2) remaining in the at...

We report the measurement of the natural isotope ratios of nitrogen and carbon in subcellular volumes of individual cells among a population of cultured cells using a multi-isotope imaging mass spectrometer (MIMS), [MIMS is the prototype of the NanoSIMS 50, Cameca, France.] We also measured the nitrogen and carbon isotope ratio in cells after they had been cultured in media enriched with the am...