Light-Induced pH Gradients in Isolated Spinach Chloroplasts

1976 ◽  
Vol 3 (2) ◽  
pp. 141 ◽  
Author(s):  
WS Chow ◽  
AB Hope
Keyword(s):  
Fluorescence Quenching ◽  
External Medium ◽  
Chloride Ions ◽  
Buffering Capacity ◽  
Small Decrease ◽  
Ph Gradients ◽  
Actinic Light ◽  
Ionic Relations ◽  
Kinetics Of ◽  
Uptake And Release

The fluorescence quenching of certain fluorescent, weakly ionizing amines has been used to estimate the pH difference (ΔpH) between the intrathylakoid spaces of chloroplasts and the external medium under various conditions. The amines N-(1-naphthyl)ethylenediamine and 9-aminoacridine gave consistent and similar estimates of ΔpH provided the concentration ranges 0.25 - 2 μM and 0.05 - 0.5 μM, respectively, were not exceeded. Values for ΔpH of up to 4 units were estimated for control chloroplasts. Only a small decrease in ΔpH was caused by FCCP and DCMU concentrations that decreased photophosphorylation rates to 10-20% of control. The kinetics of the onset and decay of ΔpH, and of the uptake and release of protons by the chloroplasts, were followed after the sudden application or withdrawal of actinic light. These kinetics suggest a model for the ionic relations of stripped chloroplasts with internal buffering capacity, [α], and dissociation constant, Ka, as parameters. At pH8, [α] is about 80 mol m-3 and Ka is 0.07 mol m-3 (pKa = 4.15). The model is successful in predicting the relation between [H+]I (the internal proton concentration) and ΔH+o (the light-driven uptake of protons from the external medium), as well as the size of ΔH+o , but needs extending to deal with published experiments on the light-driven translocation of chloride ions.

Kinetics of the fluorescence quenching of quinine bisulphate by chloride ions in polyvinyl alcohol solutions and films

1978 ◽  
Vol 20 (7) ◽  
pp. 1798-1806 ◽  
Author(s):  
V. Myuller ◽  
I.I. Kaletchitz ◽  
H.G.O. Bekker ◽  
M.G. Kuz'min ◽  
V.P. Zubov
Keyword(s):  
Fluorescence Quenching ◽  
Polyvinyl Alcohol ◽  
Chloride Ions ◽  
Kinetics Of

Kinetics of O2 uptake and release by human erythrocytes studied by a stopped-flow technique

1985 ◽  
Vol 58 (4) ◽  
pp. 1215-1224 ◽  
Author(s):  
K. Yamaguchi ◽  
D. Nguyen-Phu ◽  
P. Scheid ◽  
J. Piiper
Keyword(s):  
Time Course ◽  
External Medium ◽  
Human Erythrocytes ◽  
Stopped Flow ◽  
Diffusion Limitation ◽  
O2 Uptake ◽  
Intracellular Diffusion ◽  
Transfer Conductance ◽  
Kinetics Of ◽  
Uptake And Release

The kinetics of O2 uptake into and release from human erythrocytes was investigated at 37 degrees C by a stopped-flow technique. From the time course of O2 saturation (SO2) change a specific transfer conductance of erythrocytes for O2 (GO2) was calculated. The following results were obtained: 1) GO2 decreased in the course of O2 uptake, but initial GO2 was nearly independent of SO2 at which uptake started; 2) addition of albumin to the medium reduced GO2; 3) increasing dithionite concentration in the medium in O2-release experiments progressively enhanced GO2, which became virtually constant for nearly the entire course of release; and 4) O2 uptake and O2 release (without dithoite) in the same SO2 range yielded very similar GO2. These results suggested that O2 uptake and release were importantly limited by diffusion through the external medium and that in the SO2 range between 0.3 and 0.8, chemical reaction exerted little limiting effect. Since O2 release at the highest dithionite concentration (40 mmol/l) appeared to be virtually unlimited by external diffusion, GO2 measured under these conditions, averaging 8.7 ml X min-1 X Torr-1 X ml erythrocytes-1, was considered to mainly reflect intracellular diffusion limitation. The corresponding specific transfer conductance for O2 transfer in whole blood (hematocrit, 0.45) is 3.9 ml X min-1 X Torr-1 X ml blood-1.

The effect of external salinity on drinking rate and rectal secretion in the larvae of the saline-water mosquito Aedes taeniorhynchus

1977 ◽  
Vol 66 (1) ◽  
pp. 97-110
Author(s):  
T. J. Bradley ◽  
J. E. Phillips
Keyword(s):  
Sea Water ◽  
External Medium ◽  
Narrow Range ◽  
Saline Water ◽  
Fluid Secretion ◽  
Osmotic Concentration ◽  
Drinking Rate ◽  
Aedes Taeniorhynchus ◽  
External Salinity ◽  
Kinetics Of

1. The drinking rate of the saline-water mosquito larva Aedes taeniorhyncus (100 nl.mg-1.h-1) is unaffected by the salinity of the external medium, but is directly proportional to the surface area of the animal. 2. Haemolymph Na+, Mg2+, K+, Cl-, SO42- and osmotic concentrations were measured in larvae adapted to 10%, 100% and 200% seawater and were found to be regulated within a narrow range. 3. With the exception of potassium, ionic concentrations in rectal secretion were found to increase with increasing concentrations of the sea water in which larvae were reared. 4. The osmotic concentration of rectal secretion was unaffected by changes in haemolymph osmotic concentration but did rise when sodium or chloride concentrations of the haemolymph were increased. High levels of these ions also stimulated the rate of fluid secretion. 5. Transport of chloride and sodium by the rectum exhibits the kinetics of allosteric rather than classical enzymes.

Na+/H+ antiporter of brush border vesicles: studies with acridine orange uptake

1982 ◽  
Vol 242 (6) ◽  
pp. F733-F739 ◽  
Author(s):  
D. G. Warnock ◽  
W. W. Reenstra ◽  
V. J. Yee
Keyword(s):  
Fluorescence Quenching ◽  
Acridine Orange ◽  
Brush Border ◽  
Membrane Vesicles ◽  
Sodium Concentration ◽  
Sodium Influx ◽  
Ph Gradients ◽  
Orange Fluorescence ◽  
Acridine Orange Fluorescence ◽  
Rate Limiting

Fluorescence quenching of acridine orange was used to characterize the generation and collapse of pH gradients by the Na+/H+ antiporter of brush border membrane vesicles prepared from rabbit renal cortex. Quenching was observed when acridine orange, a weak base, was taken up to an acidic intravesicular space. Na+/H+ exchange was examined with both Na+ uptake and efflux studies. Acridine orange fluorescence quenching demonstrated the cation specificity of the Na+/H+ antiporter (i.e., sodium and lithium) and was inhibited by amiloride. Parallel studies with nigericin, a K+/H+ antiporter, demonstrated that acridine orange responded very rapidly to pH gradients. Therefore, acridine orange equilibration was not rate limiting in our studies of the Na+/H+ antiporter. Initial rate measurements were made to obtain kinetic parameters for the Na+/H+ antiporter. In sodium influx studies, the half-maximal rate of acridine orange fluorescence change was obtained with an external sodium concentration of 13.3 +/- 0.5 mM.

scholarly journals Uptake and release kinetics of 22 polar organic chemicals in the Chemcatcher passive sampler

2013 ◽  
Vol 405 (15) ◽  
pp. 5225-5236 ◽  
Author(s):  
Etiënne L. M. Vermeirssen ◽  
Conrad Dietschweiler ◽  
Beate I. Escher ◽  
Jürgen van der Voet ◽  
Juliane Hollender
Keyword(s):  
Release Kinetics ◽  
Passive Sampler ◽  
Organic Chemicals ◽  
Kinetics Of ◽  
Uptake And Release
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