Recent progress in the studies on induction of differentiation of mouse myeloid leukemia cells with special emphasis on the studies of changes in membrane structure and function is reviewed. Furthermore, induction of differentiation of leukemia cells by modification of membrane phospholipid metabolism is described. A perspective for the development of chemotherapy of leukemia based on the findings on induction of terminal differentiation of leukemia cells is briefly described.

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Molecular interaction of polymeric drugs and their analogues with phospholipid model membranes are reviewed. Antibacterial agents can be classified into three groups, depending on their target sites in bacterial cells; the cell wall, the cytoplasmic membrane and the cytoplasm. In this article, cationic biocides which affect the cytoplasmic membrane are described in detail. Typical examples are quarternary ammonium salts and biguanides. Also described are the molecular structures of the cytoplasmic membrane and the cell wall of Gram-positive and Gram-negative bacteria. The interactions of divalent cations and basic proteins with phospholipid bilayers are summerized and correlated to the mode of action of the polycation-type biocides. The specific interaction of the polycation-type biocides with acidic species in the membrane is discussed in comparison with that of monomeric biocides.

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Biospecific affinity is retained by immobilizing a molecular recognizable biosubstance on the surfaces of synthetic membranes. A biospecific affinity membrane adsorbs specifically the corresponding molecules to the surface with resulting change in transmembrane potential, which is termed “affinity membrane potential”. The concept of affinity membrane potential is generalized and successfully applied in designing biosensors including immunosensors. Theoretical and experimental aspects of affinity membrane potential is reviewed with current topics on practical use.

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Work is in progress in Japan on the utilization of ultrafiltration technique for the recovery of protein from milk and soy wheys, crushed potato and minced fish meat drain waters, and so on.
Any significant break through is not yet achieved in this field on the industrial scale application of this technique due to the adsorption of the protein on the membrane surface, resulting in a decrease of permeability and membrane efficiency. This problem needs to be handled on the top priority to popularize industrial scale application of this technique.
Ultrafiltration was applied in a fish soluble manufacturing plant, and indicated that a typical phenomenon of selected affinity exists between membrane surface and some of the components of fish protein soluble.
This finding led to the selection of suitable membranes showing minimum adsorption of protein on the surface, which led to the concentration of fish protein solution with high degree of efficiency through ultrafiltration

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When colloidal solutions containing macromolecules such as protein are treated by ultrafiltration, the gel layer is formed on the membrane surface and shows large permeation resistance. Thus, various effective cleaning methods for the gel layer have been examined. In this work, electro-ultrafiltration was studied aiming the practical applications.
The membranes used were of commercial tubular type, which are suited for treatment of solutions containing suspended solids, and egg protein (ovalbumin) was mainly used as solute. Experiments were performed under the conditions of laminar flow, 0-7 atm of pressure, 20 C of temperature and 0-20V of voltage.
Results showed effective recovery of flux and retarded gel formation under the controlled electric field. Moreover, the molecular fractionation was also done effectively by adopting this method.

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Membrane formation process of cellulose acetate (CA) for ultrafilter and the performance of the resulting membrane were studied. The membranes coagulated from a dimethyl sulfoxede (DMSO) solution of CA with water have a wide range of ultrafiltration rates (UFR) and high rejections of protein. These membranes have also good permeability properties for low and middle molecular weight (approximate 1000) molecules. It is assumed that a low coagulation value of DMSO causes the rapid precipitation of CA polymer-aggregate network, forming a porous membrane structure. Water permeability increases by diluting the composition of casting solutions, i.e., UFR is proportional to the third power of DMSO/CA ratio. A packed-bed-like membrane structure is proposed from the observation of electron microscanning and the above consideration of permeability properties.

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