Proteins are synthesized by translation of mRNA. Their functions are regulated by posttranslational modifications　such as phosphorylation due to change in their structure as well as the physical and chemical properties.　In this review article, we introduced in our experiences that phosphorylation and de-phosphorylation of erythrocyte　membrane skeletal proteins such as spectrin and protein 4.1 (4.1R) change their interactions with binding partners　with modification of membrane mechanical functions.

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Oxygen is essential to most forms of life, but too much oxygen is harmful and can elicit tissue damage. Living　creatures, therefore, have a tightly regulated system to deliver the necessary amount of oxygen to specific tissues at　the right time. Red blood cells are ideal vehicles for delivering oxygen to tissues. Band 3 protein is the major membrane　protein of red blood cells. The major membrane protein supports the oxygen delivering system by its anion　exchange activity, cooperating with carbonic anhydrase and hemoglobin. Band 3 protein has unique structure within　the molecule. Here, we briefly review the structure and function of band 3 protein.

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The life span of human red blood cells (RBCs) is approximately for 120 days, and finally destroyed in reticuloendothelial　systems. In pathological conditions, RBCs fall into premature death, i.e. hemolysis. Recent studies have　unveiled that senescent RBCs as well as RBCs of hemolytic anemia subjects shared the common feature of exposure　of phosphatidylserine (PS) in the outer leaflet of the RBC membrane. In addition, dying RBCs showed morphological　and biochemical alterations resembling to apoptosis of nucleated cells such as cell shrinkage and protein degradation.　In this review, mechanisms and physiological significance of PS externalization triggered by oxidative stress　are discussed.

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Flow cytometry (FCM) is a useful tool to detect phenotypes of blood cells. Paroxysmal nocturnal hemoglobinuria　(PNH), an acquired hematopoietic stem cell disorder, is characterized by its affected blood cells defective in the　expression of glycosyl phosphatidylinositol (GPI)-anchored proteins. GPI-anchored membrane proteins on the red　blood cells (RBC) include two major complement-regulatory membrane proteins, CD55 and CD59. The most characteristic　clinical feature of PNH, intravascular hemolysis of PNH-affected RBC, is induced by the complement-mediated　lysis of CD55- and CD59-negative PNH-RBC. In addition to the RBC membrane defects, leukocytes and platelets　are also defective in the expression of GPI-anchored proteins, because of the PNH mutations occurred in the pluripotential　hematopoietic stem cells. The GPI-anchored proteins with cell-lineage specificity, CD16b in neutrophils and　CD14 in monocytes, are also shown to be deficient in PNH by FCM. We recently applied FCM to the demonstration　of CD59-deficient populations in reticulocytes. FCM is also useful to demonstrate RBC membrane alteration in the　aspects of lipids associated with the procoagulant pathophysiology in PNH.

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Blood transfusion is an important therapy even at the developed present medicine. The main problems impeding　progress in blood transfusion are the inconsistency of supply and the risk for infection of various microorganisms.　Therefore, increased interest in the use of human stem cells has emerged following significant progress in ongoing　stem cell biology research to procure a large quantity of safe blood for therapeutic transfusion. Although it is at present　not possible to predict which types of stem cells will be best suitable for the efficient production of erythrocytes,　the isolation of human embryonic stem cells and the discovery of adult stem cells (tissue stem cells) taken together　give substance to hopes that novel principles may be developed in the procuration of blood cells for transfusion. To　achieve this, however, we have to solve a number of technical and ethical problems.

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Calcium ion-dependent eccytosis, also called exocytosis, causes dynamic structural changes in the cell membrane　to play pivotal roles in various physiological processes in neuronal and endocrine cells. It also has functions in repair　of damaged plasma membranes. This review issue describes basics and recent topics for the underlying mechanisms　for this dynamic processing of the cellular membrane.

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A basic extractant Aliquat 336 dissolved in a mixture of water and ethanol was impregnated to carboxypentyl-amino　(CPA)-group-containing polymer chains grafted onto a porous hollow-fiber membrane. The CPA group was introduced　into the graft chain by a reaction of the epoxy group of poly-glycidyl methacrylate (GMA) chain grafted onto　the porous hollow-fiber membrane with 6-aminohexanoic acid. The electrostatic interaction between the carboxyl　moiety of the CPA group and the quarternary ammonium group of Aliquat 336 gave rise to a high-density impregnation　of Aliquat 336. A higher water volume fraction in the mixture of water and ethanol used as a solvent of Aliquat　336 induced a higher extension of the graft chain, resulting in an increase in the amount of Aliquat 336 impregnated.　In addition, a higher Aliquat 336 concentration produced a higher amount of Aliquat 336 impregnated. A water volume　fraction of 0.33 and an Aliquat 336 concentration of 10% were selected on the basis of a trade-off between the　amount of Aliquat 336 impregnated and the liquid permeability. The pure water flux of porous hollow-fiber membrane　with 1.2 mol Aliquat 336 per kg GMA-grafted porous hollow-fiber membrane was 2.5 m/h at 0.1 MPa and 298　K. During the permeation of 100 mg-Pt/L platinum chloride solution (pH 4.0) through the pores of the Aliquat 336-　impregnated porous hollow-fiber membrane, platinum complex ions (PtCl6 2–) were captured by Aliquat 336 impregnated　to the graft chain, while the permeation pressure required for a constant flow rate increased. The breakthrough　binding capacity of the Aliquat 336-impregnated porous hollow-fiber membrane for platinum was 0.37 mol　per kg of the GMA-grafted porous hollow-fiber membrane.

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The basic design concept of SWC5 launched this time consists with high permeability and high salt rejection. In general, high permeability and high salt rejection are in a trade-off relation. However, SWC5 successfully achieves high flow without sacrificing salt rejection significantly. This high flow makes it possible to operate at lower pressures than the conventional seawater RO when applying to seawater, to help operate better economics in seawater desalination as a result. SWC5 has already installed in several large scale seawater desalination plants and has been contributing to produce high quality low salinity water with lower operating cost.

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