Role of the Ca2+ion concentration gradient in the adenosine 5'-triphosphate-inorganic phosphate exchange catalyzed by sarcoplasmic reticulum

Biochemistry ◽  
1974 ◽  
Vol 13 (24) ◽  
pp. 5032-5038 ◽  
Author(s):  
Leopoldo De Meis ◽  
Maria da G. C. Carvalho
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Concentration Gradient ◽  
Inorganic Phosphate ◽  
Ion Concentration ◽  
Phosphate Exchange

THE EFFECTS OF ELASTIC STIFFENING ON THE EVOLUTION OF THE STRESS FIELD WITHIN A SPHERICAL ELECTRODE PARTICLE OF LITHIUM-ION BATTERIES

2013 ◽  
Vol 05 (04) ◽  
pp. 1350040 ◽  
Author(s):  
WENBIN ZHOU ◽  
FENG HAO ◽  
DAINING FANG
Keyword(s):  
Stress Field ◽  
Lithium Ion Batteries ◽  
Internal Stress ◽  
Concentration Gradient ◽  
Concentration Field ◽  
Lithium Ion ◽  
Coupling Model ◽  
Ion Concentration ◽  
Hysteresis Phenomenon ◽  
Mechanical Coupling

Poor cyclic performance of lithium-ion batteries is calling for efforts to study its capacity attenuation mechanism. The internal stress field produced in the lithium-ion battery during its charging and discharging process is a major factor for its capacity attenuation, research on it appears especially important. We established an electrochemical –mechanical coupling model with the consideration of the influence of elastic stiffening on diffusion for graphite anode materials. The results show that the inner stress field strongly depends on the lithium-ion concentration field, greater concentration gradients lead to greater stresses. The evolution of the stress field is similar to that of the concentration gradient but lags behind it, which shows hysteresis phenomenon. Elastic stiffening can lower the concentration gradient and increase elastic modulus, which are two major factors influencing the inner stress field. We conclude that the latter is more dominant compared to the former, and elastic stiffening acts to increasing the internal stress.

scholarly journals Role of Ca2+ in pyruvate dehydrogenase interconversion in brain mitochondria and synaptosomes

1985 ◽  
Vol 227 (1) ◽  
pp. 129-136 ◽  
Author(s):  
R G Hansford ◽  
F Castro
Keyword(s):  
Plasma Membrane ◽  
Steady State ◽  
Pyruvate Dehydrogenase ◽  
Maximal Activity ◽  
Brain Mitochondria ◽  
Ruthenium Red ◽  
Ion Concentration ◽  
Maximal Effect ◽  
State Content

The steady-state content of active (dephospho) pyruvate dehydrogenase (PDHA) of suspensions of coupled rat brain mitochondria oxidizing succinate was found to be markedly increased with increasing free Ca2+ ion concentration of the medium, with a half-maximal effect at 10(-6.43) M Ca2+. Other ions were present in these studies at concentrations appropriate for the cytosol. Depolarization of the plasma membrane of synaptosomes caused an increase in the steady-state content of PDHA, with veratridine giving a larger increase than depolarization by 33 mM-KCl. Values were 68 +/- 1% (n = 13) and 81 +/- 1% (n = 19) of maximal activity, for control incubations and incubations in the presence of 30 microM-veratridine, respectively. Measurements of cytosolic free Ca2+ concentrations ([Ca2+]cyt.) in these suspensions of synaptosomes, with the use of the fluorescent Ca2+-indicator Quin-2, indicated an increase on depolarization, with the change due to 30 microM-veratridine being larger in extent than that due to 33 mM-KCl. Values were 217 +/- 21 nM (n = 15), 544 +/- 48 nM (n = 15) and 783 +/- 75 nM (n = 14) for control, KCl-depolarized and veratridine-depolarized synaptosomes respectively. Experiments in which synaptosomes were treated with Ruthenium Red, an inhibitor of mitochondrial Ca2+ uptake, gave much lower resting contents of PDHA (42 +/- 2% of maximal), but failed to prevent totally an increase on depolarization. Addition of an excess of EGTA to the synaptosomal suspension just before the addition of veratridine resulted in a partial diminution in the response of PDHA content. Parallel studies with Quin-2 indicated no increase in [Ca2+]cyt. on addition of veratridine, under these conditions. Thus an increase in [Ca2+]cyt. forms only a part of the mechanism whereby pyruvate dehydrogenase interconversion responds to depolarization. A decrease in the ATP/ADP ratio may also be important, as inferred from the results of experiments with ouabain, which inhibits the Na+ + K+-dependent ATPase.

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