scholarly journals The effect of the coupled oxidation of substrate on the permeability of blowfly flight-muscle mitochondria to potassium and other cations

1972 ◽  
Vol 126 (3) ◽  
pp. 689-700 ◽  
Author(s):  
R. G. Hansford ◽  
A. L. Lehninger
Keyword(s):  
Light Scattering ◽  
Flight Muscle ◽  
Unit Area ◽  
Membrane Surface ◽  
Mitochondrial Matrix ◽  
Exposed Area ◽  
Muscle Mitochondria ◽  
Area 5 ◽  
Choline Phosphate ◽  
Permeant Anion

1. Blowfly flight-muscle mitochondria respiring in the absence of phosphate acceptor (i.e. in state 4) take up greater amounts of K+, Na+, choline, phosphate and Cl-(but less NH4+) than non-respiring control mitochondria. 2. Uptake of cations is accompanied by an increase in the volume of the mitochondrial matrix, determined with the use of [14C]-sucrose and3H2O. The osmolarity of the salt solution taken up was approximately that of the suspending medium. 3. The [14C]sucrose-inaccessible space decreased with increasing osmolarity of potassium chloride in the suspending medium, confirming that the blowfly mitochondrion behaves as an osmometer. 4. Light-scattering studies showed that both respiratory substrate and a permeant anion such as phosphate or acetate are required for rapid and massive entry of K+, which occurs in an electrophoretic process rather than in exchange for H+. The increase in permeability to K+and other cations is probably the result of a large increase in the exposed area of inner membrane surface in these mitochondria, with no intrinsic increase in the permeability per unit area. 5. No increase in permeability to K+and other cations occurs during phosphorylation of ADP in state 3 respiration.

Sonochemical Preparation of Polymer Microcapsules

2013 ◽  
Vol 631-632 ◽  
pp. 86-89 ◽  
Author(s):  
Sheng Wei Guo ◽  
Gu Xia Wang
Keyword(s):  
Free Energy ◽  
Light Scattering ◽  
Shell Thickness ◽  
Materials Science ◽  
Unit Area ◽  
Hollow Structure ◽  
Important Application ◽  
Interface Condition ◽  
Sonochemical Method ◽  
Interface Free Energy

Polymer microcapsules have important application in the fields of biochemistry and materials science owing to their unique structures and functions. Poly(styrene-methyl methacrylate) (PS-co-PMMA) microcapsules were prepared through sonochemical method. The results reveal that it is difficult to form a microcapsule structure from neat styrene (St). However, MMA can improve the interface condition for its higher hydrophilicity. Therefore, it is easier to form hollow structure because polymer microcapsules have a lower interface free energy per unit area. FTIR results confirm that polymer microcapsules have both the typical peaks of PS and PMMA. The results of dynamic light scattering (DLS) and TEM show that PS-co-PMMA microcapsules are uniform in size(about 100 nm in diameter and 20~25 nm in shell thickness).

scholarly journals The control of tricarboxylate-cycle oxidations in blowfly flight muscle. The steady-state concentrations of citrate, isocitrate 2-oxoglutarate and malate in flight muscle and isolated mitochondria

1975 ◽  
Vol 146 (3) ◽  
pp. 527-535 ◽  
Author(s):  
R N Johnson ◽  
R G Hansford
Keyword(s):  
Redox State ◽  
Flight Muscle ◽  
Total Content ◽  
Phormia Regina ◽  
Experimental Conditions ◽  
Main Determinant ◽  
Muscle Mitochondria ◽  
Isolated Mitochondria ◽  
Tricarboxylate Cycle

1. Blowfly (Phormia regina) flight-muscle mitochondria were allowed to oxidize pyruvate under a variety of experimental conditions, and determinations of the citrate, isocitrate, 2-oxoglutarate and malate contents of both the mitochondria and the incubation medium were made. For each intermediate a substantial portion of the total was present within the mitochondria. 2. Activation of respiration by either ADP or uncoupling agent resulted in a decreased content of citrate and isocitrate and an increased content of 2-oxoglutarate and malate when the substrate was pyruvate, APT and HCO3 minus. Such a decrease in citrate content was obscured when the substrate was pyruvate and proline owing to a large rise in the total content of tricarboxylate-cycle intermediates in the presence of proline and ADP. 3. An experiment involving oligomycin and uncoupling agent demonstrated that the ATP/ADP ratio is the main determinant of flux through the tricarboxylate cycle, with the redox state of nicotinamide nucleotide being of lesser importance. 4. Addition of ADP and Ca-2+ to activate the oxidation of both glycerol 3-phosphate and pyruvate, simulating conditions on initiation of flight, gave a decrease in citrate and isocitrate and an increase in 2-oxoglutarate and malate content. 5. There was a good correlation between these results with isolated flight-muscle mitochondria and the changes found in fly thoraces after 30s and 2 mihorax. 6. It is concluded that NAD-isocitrate dehydrogenase (EC 1.1.1.41) controls the rate of pyruvate oxidation in both resting fly flight muscle in vivo and isolated mitochondria in state 4 (nomenclature of Change & Williams, 1955).

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