SULFUR ISOTOPE EFFECTS IN THE HYDROGEN ION DECOMPOSITION OF THIOSULFATE

1965 ◽  
Vol 43 (10) ◽  
pp. 2802-2811 ◽  
Author(s):  
U. Agarwala ◽  
C. E. Rees ◽  
H. G. Thode
Keyword(s):  
Sulfur Isotope ◽  
Isotope Effects ◽  
Hydrogen Ion ◽  
Decomposition Mechanisms ◽  
Good Agreement

Sulfur isotope effects in the decomposition of thiosulfate have been studied. There are two distinct intermolecular isotope effects and these have been used to examine various mechanisms for the reaction. By use of the theory of competing isotope reactions the thiosulfate decomposition mechanisms of La Mer and Davis have been shown to predict isotope effects not in accord with experiment, while a simple bimolecular three-centered reaction has been shown to predict sulfur and sulfite isotope effects in good agreement with the experimentally determined values of 1.9% and 0.9%.

Sulfur isotope effects in the hydrogen ion decomposition of polythionates

1967 ◽  
Vol 45 (2) ◽  
pp. 181-187 ◽  
Author(s):  
U. Agarwala ◽  
C. E. Rees ◽  
H. G. Thode
Keyword(s):  
Sulfur Isotope ◽  
Isotope Effects ◽  
Experimental Results ◽  
Hydrogen Ion ◽  
Rate Controlling Step ◽  
Sulfur Bond

The sulfur isotope effects in the decomposition of tri-, tetra-, and penta-thionate have been studied. There are three distinct intermolecular and three distinct intramolecular isotope effects. The experimental results show that the decomposition of these polythionates may be described in terms of a model where the rate-controlling step is the cleavage of a sulfur–sulfur bond, and that the appropriate cleavage forms are (S2O32−) (SO3), (S3O3) (SO32−), and (S4O3) (SO32−) for tri-, tetra-, and penta-thionate, respectively.

Calculationof Equilibrium Isotope Effects in a Conformationally Mobile Carbocation

1989 ◽  
Vol 44 (5) ◽  
pp. 480-484 ◽  
Author(s):  
Martin Saunders ◽  
Gary W. Cline ◽  
Max Wolfsberg
Keyword(s):  
Theoretical Calculations ◽  
Isotope Effects ◽  
Stable Solution ◽  
Constant Matrix ◽  
Force Constant Matrix ◽  
Hydride Shift ◽  
Rapid Equilibrium ◽  
Theory And Experiment ◽  
Good Agreement ◽  
C Nmr

The rapid, degenerate 1,2-hydride shift in 2,3-dimethyl-2-butyl cation in stable solution in SbF5/SO2C1F was perturbed by deuterium and 13C leading to splittings observed by 13C NMR spectroscopy over a range of temperatures. Accurate values for equilibrium isotope effects were obtained from these data. Theoretical calculations of the equilibrium isotope effects were performed using the Gaussian-86 program to obtain an optimized geometry and the Cartesian force constant matrix, followed by the program QUIVER which applies the Bigeleisen-Mayer method. When all of the conformers, which are in rapid equilibrium, were considered specifically, quite good agreement between theory and experiment was obtained.

Stable isotope fractionation by Clostridium pasteurianum. 4. Sulfur isotope fractionation during enzymatic S3O62−, S2O32−, and SO32− reductions

1981 ◽  
Vol 27 (8) ◽  
pp. 824-834
Author(s):  
G. I. Harrison ◽  
E. J. Laishley ◽  
H. R. Krouse
Keyword(s):  
Stable Isotope ◽  
Isotope Fractionation ◽  
Sulfur Isotope ◽  
Isotope Effects ◽  
Growth Conditions ◽  
Enzyme Concentration ◽  
Clostridium Pasteurianum ◽  
Relative Reduction ◽  
Stable Isotope Fractionation ◽  
Sulfur Isotope Fractionation

Cell-free extracts from Clostridium pasteurianum grown on SO32− utilize H2 to reduce S3O62−, S2O32−, and SO32− to H2S at a much faster rate than extracts from SO42−-grown cells. This further supports the concept of an inducible dissimilatory type SO32− reductive pathway in this organism. 35S dilution experiments further support the concept that S3O62− and S2O32− are pathway intermediates. The inducible SO32− reductase is ferredoxin linked and the kinetics of the reduction and the sulfur isotope fractionation of the product can be altered by altering the growth conditions. The attending sulfur isotope fractionations are similar to those observed during the chemical decomposition of these compounds. In the case of S2O32−, 35S labelling experiments verified the conclusions derived from the stable isotope fractionation data concerning the relative reduction rates of the sulfane and sulfonate sulfurs. The reduction rates were also affected by enzyme concentration. The integrity of the whole cell is a necessary requirement for the large inverse isotope effects previously reported.

Thiosulfate formation and associated isotope effects during sulfite reduction by Clostridium pasteurianum

1979 ◽  
Vol 25 (6) ◽  
pp. 719-721 ◽  
Author(s):  
L. A. Chambers ◽  
P. A. Trudinger
Keyword(s):  
Isotope Fractionation ◽  
Sulfur Isotope ◽  
Isotope Effects ◽  
Clostridium Pasteurianum ◽  
Stages Of Growth ◽  
Bacterial Cultures ◽  
Sulfur Isotope Fractionation ◽  
Secondary Chemical Reaction ◽  
Secondary Chemical ◽  
Isotopic Effects

During growth of Clostridium pasteurianum on sulfite, approximately half the sulfite was reduced to sulfide and half to thiosulfate. Sulfide was enriched in 32S or 34S at different stages of growth and thiosulfate was enriched in 32S, particularly in the sulfane atom.It is suggested that thiosulfate in these bacterial cultures arose from a secondary chemical reaction. The chemical formation of thiosulfate from sulfide and sulfite was also accompanied by sulfur isotope fractionation. The implications of these results with respect to 'inverse' isotopic effects are discussed.

scholarly journals Effects of Iron and Nitrogen Limitation on Sulfur Isotope Fractionation during Microbial Sulfate Reduction

2012 ◽  
Vol 78 (23) ◽  
pp. 8368-8376 ◽  
Author(s):  
Min Sub Sim ◽  
Shuhei Ono ◽  
Tanja Bosak
Keyword(s):  
Nitrogen Fixation ◽  
Sulfate Reduction ◽  
Isotope Fractionation ◽  
Sulfur Isotope ◽  
Isotope Effects ◽  
Reducing Power ◽  
Sulfate Reducing ◽  
Microbial Sulfate Reduction ◽  
Sulfur Isotope Fractionation ◽  
S Isotope

ABSTRACTSulfate-reducing microbes utilize sulfate as an electron acceptor and produce sulfide that is depleted in heavy isotopes of sulfur relative to sulfate. Thus, the distribution of sulfur isotopes in sediments can trace microbial sulfate reduction (MSR), and it also has the potential to reflect the physiology of sulfate-reducing microbes. This study investigates the relationship between the availability of iron and reduced nitrogen and the magnitude of S-isotope fractionation during MSR by a marine sulfate-reducing bacterium, DMSS-1, aDesulfovibriospecies, isolated from salt marsh in Cape Cod, MA. Submicromolar levels of iron increase sulfur isotope fractionation by about 50% relative to iron-replete cultures of DMSS-1. Iron-limited cultures also exhibit decreased cytochromec-to-total protein ratios and cell-specific sulfate reduction rates (csSRR), implying changes in the electron transport chain that couples carbon and sulfur metabolisms. When DMSS-1 fixes nitrogen in ammonium-deficient medium, it also produces larger fractionation, but it occurs at faster csSRRs than in the ammonium-replete control cultures. The energy and reducing power required for nitrogen fixation may be responsible for the reverse trend between S-isotope fractionation and csSRR in this case. Iron deficiency and nitrogen fixation by sulfate-reducing microbes may lead to the large observed S-isotope effects in some euxinic basins and various anoxic sediments.

Isotope effects in the transfer of vibrational energy in gaseous collisions

1963 ◽  
Vol 272 (1351) ◽  
pp. 481-489 ◽  
Keyword(s):  
Energy Transfer ◽  
Vibrational Energy ◽  
Isotope Effects ◽  
Methyl Chloride ◽  
Steric Factor ◽  
The Other ◽  
Accurate Information ◽  
Effects Of Rotation ◽  
Catalytic Effects ◽  
Good Agreement

Previously available studies of isotope effects in catalysts for the transfer of vibrational energy have been extended by comparing catalytic effects of NH 3 and ND 3 . For each of the three vibrators, ethylene, methyl chloride, and cyclo propane, vibration-vibration transfer appears to be only of subsidiary importance in the overall catalysis observed. With these vibrators, good agreement is found between observed relative efficiencies of H 2 O and D 2 O, and H 3 N and D 3 N as energy transfer catalysts. With ethylene, relative efficiencies of H 3 N and D 3 N can probably be attributed to mass differences. But even after allowing for mass differences of the isotopic molecules, collisions with some of the other vibrators show residual predominance of the hydrogen over the deuterium derivative as catalyst. This can possibly be attributed to effects of rotation during a collision, on the steric factor. To advance our knowledge about energy transfer further, more accurate information is needed about the origin and magnitude of inter-molecular repulsions.

KINETIC SULFUR ISOTOPE EFFECTS IN AROMATIC BROMODESULFONATION

1966 ◽  
Vol 44 (3) ◽  
pp. 363-378 ◽  
Author(s):  
B. T. Baliga ◽  
A. N. Bourns
Keyword(s):  
Sulfur Isotope ◽  
Isotope Effects ◽  
Ion Concentration ◽  
Step Process ◽  
Bromide Ion ◽  
Alternate Mechanism ◽  
One Step ◽  
The Individual ◽  
Step Mechanism

Both bromodeprotonation and bromodesulfonation occur during aqueous bromination of sodium p-methoxybenzenesulfonate, A, and potassium 1-methylnaphthalene-4-sulfonate, B. Whereas for A the bromodeprotonation increases appreciably in amount as the bromide ion concentration is raised, this reaction takes place to a relatively small extent for the less reactive B. A reinvestigation of the kinetics of bromination and a determination of sulfate yields for both of these compounds over a range of bromide ion concentration of 0 to 0.5 M have been made to evaluate the individual rates of these two competing reactions. The kinetic data for the bromodesulfonation of A favor a two-step mechanism with Br2 as the brominating species, but are not considered to eliminate completely a one- or two-step process involving Br+ (or H2OBr+). For B, the kinetics allow either a one- or two-step mechanism with molecular bromine as the brominating agent.Kinetic sulfur isotope effects (k32/k34) have been measured for the bromodesulfonation of A at different bromide ion concentrations. The observed effects are: at [Br−] = 0, 0.3%; at [Br−] = 0.03 M, 1.3%; at [Br−] = 0.5 M, 1.7%. These results confirm the two-step mechanism favored by kinetics and allow the rejection of the alternate mechanism with Br+ (or H2OBr+) as the brominating species. A similar study of B gave the following results: at [Br−] = 0, 0.2%; at [Br−] = 0.25 M, 0.3%; at [Br−] = 0.5 M, 0.4%; at [Br−] = 2.0 M, 0.8%. These results establish the two-step mechanism for this compound and completely eliminate the alternate one-step process.

scholarly journals Sulfur Isotope Effects of Dissimilatory Sulfite Reductase

2015 ◽  
Vol 6 ◽  
Author(s):  
William D. Leavitt ◽  
Alexander S. Bradley ◽  
André A. Santos ◽  
Inês A. C. Pereira ◽  
David T. Johnston
Keyword(s):  
Sulfur Isotope ◽  
Isotope Effects ◽  
Sulfite Reductase ◽  
Dissimilatory Sulfite Reductase
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