Ion permeability of maize root membrane vesicles: Studies with light scattering |
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Authors: | J Sklenar B C Loughman |
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Institution: | (1) Institute of Botany, Slovak Academy of Sciences, Dubravska cesta 14, 842 23 Bratislava, Slovakia;(2) Department of Plant Sciences, University of Oxford, South Parks Road, OX1 3RB Oxford, UK |
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Abstract: | A possible modulation of permeabilities of membrane vesicles to anions and cations was explored by light scattering techniques, evaluated by measuring the capacity of the vesicles to shrink and swell in response to changes of the osmolarity of the incubation medium. Membrane fractions were obtained by phase partition. Purity was evaluated by detection and quantification of membrane enzyme markers: vanadate-sensitive ATPase for the plasma membrane, nitrate-sensitive ATPase for the tonoplast and azide-sensitive ATPase for mitochondria. Membrane vesicles (250 g protein) were exposed to hypertonic solutions of salts (0.6 osmolar). Kinetics of the changes in apparent absorbance at 546 nm were observed by the addition of potassium, nitrate and chloride salts. The diffusion of ions into vesicles was induced by an osmotic gradient across the membrane and brought about volume changes of vesicles. Upon addition of vesicles to the different solutions the following ion permselectivity sequences were observed: PNO
3
– >PCl
–>PSO
4
2– and PK
+ PNa
+>PNH
4
+.Abbreviations ATP
adenosine 5 -triphosphate
- EDTA
ethylene diaminetetraacetic acid
- Tris-Mes
(Trishydroxymethyl]aminomethane, Mes-(2-N-Morpholino]ethanesulfonic acid)
- PEG
polyethylene glycol |
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Keywords: | light scattering technique membrane marker membrane vesicles permeability phase partition |
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