Department of Botany, Faculty of Science, University of Tokyo, Hongo, Tokyo 113To study the electrogenic mechanism of the plant plasma membrane, intracellular chemical composition of Chara australis, a Characeae, was modified by the intracellular perfusion. It was suggested that the H⁺-extruding pump which is fueled by Mg·EATP is operating in the electrogenesis. Activity of the H⁺-pump was maximum at pH_o 5.4-8.4 and at pHi 7. Light activates H⁺-pump and hyperpolarizes the membrane (light-induced potential change; LPC). Since LPC was not elicited in chloroplast-free Spirogyra cell which was prepared by cell-centrifugation, involvement of photosynthesis in LPC was concluded. Importance of electron transport in photosynthesis was suggested.
There is another mechanism of electrogenesis in Chara cells. When internal ATP or Mg²⁺ concentration was lowared greatly, the plasma membrane depolarized. When such a cell was stained with neutral red, a rapid light-induced potential change (rLPC) was observed. On illumination the membrane potential approached K⁺-equilibrium potential across th e plasma membrane and K⁺-channel inhibitors suppressed rLPC, evidence that rLPC is caused by activation of K⁺-channel. When the cell was made chloroplast-free by the centrifugation, rLPC was removed, and it was recovered by introducing spinach chloroplasts into the chloroplast-free Chara cell. Involvement of electron transport in rLPC was also suggested.

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Recently, separation of dispersed systems using membranes such as reverse osmosis, electrodialysis, ultrafiltration and electro-ultrafiltration have been widely used in many industries.
The characteristics of separation using membranes are related to not only material of membrane and structure of membrane but also electric double layer at interface and electrokinetic phenomena. Therefore, the electrokinetic phenomena are important for the separation of dispersed systems using membranes.
In this paper, the effects of electrokinetic phenomena on characteristics of separation using membrane and applications of the electrokinetic phenomena to separation of dispersed systems using membrane are mainly discussed.

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A bimolecular membrane of phospholipids such as lecithin is in a state of liquid crystal capable of reversible structural modifications and its permeation property depends on such reversible change. Artificial amphiphiles with monoalkyl and dialkyl groups form multilamellar liposome composed of the bimolecular layer. Artificial amphiphiles have characteristics of both thermotropic and lyotropic mesomorphisms. The diffusive permeability of polymer/artificial amphiphiles composite membrane to water exhibits a distinct jump in the vicinity of the crystal-liquid crystal phase transition temperature.
Diffusive permeability coefficients (P) to hydrocarbon gases for polymer/liquid crystal (EBBA) composite membrane reveals a distinct increase of 100-200 times over several degrees in the crystal-liquid crystal phase transition temperature range of EBBA. P decreases with increasing the number of carbon atome below the phase transition temperature and this trend suggests that permeation is predominantly governed by diffusion process. On the other hand, above the phase trasition temperature of EBBA, P increases with an increase of the number of carbon atom. This tendency can not be explained by diffusion control mechanism but it is reasonably expected that permeation is mainly governed by solubility process.

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Ethylene-Vinyl alcohol (EVA) copolymer membrane was evaluated as a new carrier for drug delivery. The steady state permeation of prednisolone and prednisone through EVA copolymer membranes of various comonomer ratios was studied. The rate of drug permeation was found to be dependent upon the monomer composition

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The electrophoretic mobility of brush border membrane vesicles isolated from rabbit ileum was measured with a Laser Zee Autoelectrophoretic apparatus. The average value of mobility measured in a medium containing 50mM mannitol, 10mM NaCl and pH 7.37 at 20C, was^-1.85μm. s^-1.v^-1.cm. The mobility was dependent on both medium pH and the ionic strength. The isoelectric point was found to be about 4.3, the vesicles being negatively charged in the normal range of pH. The surface charge density was caluculated to be 2000-3000 per vesicle.

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