Cyanide-resistant respiration in isolated Asparagus mesophyll cells

1984 ◽  
Vol 62 (6) ◽  
pp. 1122-1126 ◽  
Author(s):  
Nancy M. Shadeed ◽  
Alan W. Bown
Keyword(s):  
Alternative Pathway ◽  
Potassium Cyanide ◽  
Antimycin A ◽  
Mesophyll Cells ◽  
Atp Levels ◽  
Energy Conserving ◽  
Sequential Addition ◽  
Tetraethylthiuram Disulfide ◽  
Energy Dependent ◽  
Cyanide Resistant Respiration

The inhibitors of oxidative phosphorylation antimycin A (0.5 μg/mL), oligomycin (0.01 mg/mL), and sodium azide (3 mM) eliminated energy-dependent H+ efflux from isolated Asparagus mesophyll cells. Antimycin A and oligomycin also reduced ATP levels by 60% or more. In contrast the same concentrations of inhibitors had little or no effect on respiratory O2 consumption. The sequential addition of potassium cyanide to give a final concentration of 5.2 μM resulted in a 60% maximum inhibition of O2 consumption. Subsequent addition of 0.2 mM disulfiram (tetraethylthiuram disulfide), a potent inhibitor of cyanide-resistant respiration, resulted in a further reduction of the oxygen consumption rate. In the absence of cyanide, 0.2 mM disulfiram inhibited O2 consumption by 40 to 80%, depending on the suspension medium. Disulfiram had little or no effect on the ATP levels which varied between 0.7 and 2.2 nmol ATP/106 cells. The results indicate that disulfiram inhibits a non-energy-conserving cyanide-resistant alternative pathway in Asparagus mesophyll cells.

The Structure of Neoprene. II. Determination of End Groups by Means of Radiosulfur

1949 ◽  
Vol 22 (4) ◽  
pp. 1092-1102 ◽  
Author(s):  
W. E. Mochel ◽  
J. H. Peterson
Keyword(s):  
Chain Transfer ◽  
Potassium Persulfate ◽  
Polymer Molecule ◽  
Cleavage Reaction ◽  
Polymer Molecules ◽  
Simple Chain ◽  
The One ◽  
Tetraethylthiuram Disulfide ◽  
Molecular Weight Fractions

Abstract By use of radioactive sulfur it has been shown that sulfur-modified Neoprene, i.e., Neoprene Type GN, is essentially a copolymer of chloroprene and sulfur in the approximate ratio of 100 chloroprene units per sulfur atom. The sulfur units, possibly disulfides, are cleaved by an alkaline emulsion of tetraethylthiuram disulfide, so that a gel polymer containing combined sulfur can thus be converted to a soluble, plastic product. The mechanism of this cleavage reaction has not been completely elucidated as yet. Potassium persulfate, used as initiator for the polymerization of Neoprene, appears to be combined with the polymer in Neoprene Type GN in amounts equivalent to 8–17 polymer molecules formed for each sulfur-cpntaining initiator fragment. However, when dodecanethiol is used as modifier, a large proportion of the polymer molecules contain essentially no combined sulfur from the persulfate, and it appears that the true initiator is the RS free radical formed by reaction of the thiol with potassium persulfate. Dodecanethiol used as a polymerization modifier or chain transfer agent is combined in a greater amount than the one thiol per polymer molecule expected on the basis of simple chain transfer. High molecular-weight fractions contained 3–4 thiol sulfur atoms per polymer molecule and the results suggest that thiol addition to the double bonds of the polymer had occurred.

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