Positionally dependent fractionation factors for the photolysis of isotopomers of N20 in natural abundance have been determined by high resolution FTIR spectroscopy at three photolysis wavelengths. Fractionation factors show clear lSN position and photolysis wavelength dependence and are in qualitative agreement with theoretical models but are twice as large. The fractionation factors increase ...

The demonstration of tissue specific isoenzymes of lactic dehydrogenase and their variations in certain diseases (1, 2, 3) has invigorated the interest for further fractionation of other serum enzymes. Recently FLODIN and KILLANDER (4) have reported on the fractionation of human serum proteins by filtration through porous dextran gel "Sephadex G-200" (4). This method exposes the proteins to ver...

[1] Recently, calcium isotope fractionation in the coccolithophore Emiliania huxleyi was shown to exhibit a significant temperature dependency. An important subsequent question in this context is whether the observed fractionation patterns are caused by temperature itself or related growth rate changes. In order to separate growth and calcification rate effects from direct temperature effects, ...

Carbon isotope fractionation by structurally and catalytically distinct ribulose-1,5-bisphosphate carboxylases from one eucaryotic and four procaryotic organisms has been measured under nitrogen. The average fractionation for 40 experiments was -34.1 per thousand with respect to the delta(13)C of the dissolved CO(2) used, although average fractionations for each enzyme varied slightly: spinach ...

Fractionation of plant compounds to produce active purified fractions is a multi-step process, time-consuming and sometimes very expensive. This paper presents a single-step fractionation of tannins from a local plant, Phyllanthus niruri Linn. using supercritical fluid extraction (SFE) method. The effects of operating conditions (pressure, temperature, flow rate, cosolvent content and ethanol-w...

We investigated the influence of organic substrates and phosphate concentration on the rates of dissimilatory microbial sulfate reduction and the 34S/32S isotopic fractionation produced by several Desulfovibrio species. Our experiments corroborate the previously reported species-specific correlation between sulfur isotope fractionation and cell-specific sulfate reduction rates. We also identify...

The currently used “kinetic-fractionation” (KF) model of the differential incorporation of water-molecule isotopologues into vapor-grown ice omits surface processes on crystal facets that may be important in temperature reconstructions. This article introduces the “surface-kinetic” fractionation model, a model that includes such surface processes, and shows that differences in deposition coeffi...

We have developed new models of the chemistry of deuterium for investigating fractionation in interstellar molecular clouds. We have incorporated the latest information on reactions which affect deuteration, extended previous models to include S-D bonds for the first time and included the gasphase chemistry of some doubly-deuterated species.We present models for a wide range of physical paramet...