Biophysical chemistry of biointerfaces is discussed along the line of a theoretical model suitable for biointerfaces, that is, a soft particle theory. In this theory, biointerfaces such as cell surfaces and their model surfaces are regarded as a solid surface covered with an ion-penetrable polyelectrolyte layer. Electrokinetic phenomena of soft particles and electrostatic interactions between soft surfaces are quite different from those for hard particles without surface structures. Recent progress in theories for interfacial electric phenomena of soft particles are reviewed.

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The conversion of soluble, nontoxic amyloid β-protein (Aβ) to aggregated, toxic Aβ rich in β-sheet structures by seeded polymerization is considered to be the key step in the development of Alzheimer’s disease. Accumulating evidence suggests that lipid rafts (microdomains) in membranes mainly composed of sphingolipids (gangliosides and sphingomyelin) and cholesterol play a pivotal role in this process. Our model membrane studies revealed the following mechanism. Soluble Aβ with unordered structures specifically binds to raft-like membranes containing a ganglioside cluster, the formation of which is facilitated by cholesterol. The membrane-bound Aβ forms an α-helix-rich structure at lower densities. At higher densities, Aβ undergoes a conformational transition to a β-sheet-rich structure that can serve as a seed for amyloid fibril formation. This model was confirmed in cellar level using rat pheochromocytoma PC12 cells. Fourier-transform infrared spectroscopic and electron micrographic studies revealed that the structures of Aβ fibrils formed in solution and lipid rafts are different. The fibrilization can be inhibited by small organic compounds and biocompatible nanogels.

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In Japan, in April 1970, the application of reverse osmosis in food processing was selected as a subject of a symposium organized by the Japanese Society of Food Science and Technology. This was followed by collaboration by companies, universities and the Ministry of Agriculture, Forestry and Fisheries on membrane technology in order to investigate the application of membrane technology in new fields. In 1982, Membrane Research Association in Food Industry (MRAFI) was founded with a aid by the Ministry of Agriculture, to promote the collaborative research with food companies and membrane companies. After the final presentations of the results of the research in MRAFI, Membrane & separation Research Circle of Food (MRC) was established by sympathizers of the membrane technologists in industry, government and university. Main membrane technologies for food processing are categorized into five types; microfiltration (MF), ultrafiltration (UF), nanofiltraion (NF), reverse osmosis (RO) and electrodialysis (ED). In these, NF has recently made great advance in regard to its practical use as a new field of membrane separation. The membrane technology has been investigated for about 40 years in Japan. And it has been steadily coming into practical use in food industry for the improvement of food quality, creation of new food products, separating the constituent parts of functional food, and energy saving.

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For adding a further value to carcasses of spent laying hens, which are produced annually 150,000 tons in Japan, we attempted to develop a large scale purification and concentration process of functional dipeptides in the chicken extract obtained from these carcasses by using a combination of ion-exchange chromatography and nanofiltration (NF). The functional dipeptides, Anserine and Carnosine, constituting with β-alanine and L-histidine (ACmix), show a basic property and can be adsorbed directly onto a cation exchange resin. The ACmix were completely separated from other elements when the chicken extract was passed through the column packed with a cation exchanger and the dipeptides were eluted from the column by using diluted alkaline solution. The major contaminated substances in the ACmix were Na+, K+ and creatinine. A NF can remove these contaminants and concentrate ACmix as a desirable purity without a heating process. Of thirteen NF membranes examined, three polyamide membranes were appropriate to this purpose. By using a mathematics model, we designed a NF process that can purify ACmix to 90% purity and concentrate to more than ten times. The ACmix had an antioxidant activity specifically to hypochlorite radicals and markedly reduced an oxidative stress in normal human volunteers in combination with vitamin C and ferulic acid.

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Microorganism elimination using MF membrane is efficient process for manufacturing good flavor liquid food. A low fouling membrane with sharp pore size distribution is necessary in these processes. The pore size influences a certainty of the sterilization. Macromolecular components in food need low fouling operation to pass through a membrane.

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In 1, 2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/fatty acid (FA) system, the analysis of the interaction between the DMPC/FA liposome and amyloid β-peptide (Aβ) was carried out by using the quartz crystal microbalance (QCM) method, together with the analysis of the compression isotherms of the DMPC/FA monolayer. The DMPC/stearic acid (SA) liposome showed the highest intensity in its interaction with Aβ through the QCM method although the slight interaction between DMPC/linoleic acids (LAs) liposome and Aβ was obtained. The compression isotherm analysis of the lipid monolayers revealed that the DMPC/SA monolayers underwent the distinct phase transfer, with which the interaction between both molecules changed from repulsive to attractive, while DMPC/linoleic acid monolayers did not.

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Bis(monoaclyglycero)phosphate (BMP), also known as lysobisphosphatidic acid (LBPA), is a unique phospholipid highly enriched in a specific membrane domain of late endosomes. We synthesized 3,3’-dipalmitoyl bis (monoacylglycero) phosphate (diC16:0 BMP) with naturally occurring sn–1, sn–1’ stereoconfiguration and characterized the thermotropic phase behavior and the membrane properties by using differential scanning calorimetry (DSC), smalland wide-angle X-ray scattering, steady-state fluorescence anisotropy measurement and epifluorescence microscopy of monolayers. In DSC, DiC16:0 BMP displayed a higher melting temperature (52.0 ℃) and a higher molar enthalpy (17.3 kcal/mol) of main phase transition than those of corresponding PG (40.1 ℃ and 9.4 kcal/mol respectively). DiC16: 0 BMP also exhibited weakly energetic broad peak at 19.5 ℃. Wide-angle X-ray scattering revealed that the diC16: 0 BMP undergoes quasi-crystalline phase → tightly packed and partly oriented gel phase → liquid crystalline phase between 10 ℃ and 60 ℃ by passing two calorimetric transitions. Steady-state anisotropy measurements of 1,6- diphenyl-1,3,5-hexatriene (DPH) and 1-(4-trimethylammonium-phenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) in diC16:0 BMP also indicated a high main transition temperature in BMP. The domain formation in monolayer showed that diC16: 0 BMP formed anisotropic domain shape while PG formed relatively circular domains. The present results, together with our recent results (Hayakawa, T., Hirano, Y., Makino, A., Michaud, S., Lagarde, M., Pageaux, JF., Doutheau, A., Ito, K., Fujisawa, T., Takahashi, H. and Kobayashi, T. (2006) Biochemistry, , 9198-9209) suggest the formation of strong inter-molecular hydrogen bonding between the BMP molecules in the membrane.

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We prepared giant vesicles using a water-in-oil emulsion containing uniform water droplets (mean diameter, 37.3 μm) as a starting material. This emulsion produced vesicles that were larger than 30 μm in diameter and that entrapped calcein with an entrapment yield exceeding 20%.

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The dehydration technology of hydrous bio ethanol utilizing the zeolite membranes and their performances obtained from the commercial operation of the anhydrous ethanol plant with a capacity of annual 10,000kL is introduced. The zeolite membranes prepared onto the porous alumina tubes by hydrothermal deposition technique are installed in the unit shells called “module” to process effectively the hydrous ethanol produced through the conventional process sequence of the fermentation and distillation steps. The hydrous ethanol vapor was successfully dried through the system of four modules connected in series. During the starting one-hundred-day operation of the commercial plant, ethanol concentrations in the product and the permeate water has been maintained around 99.8vol% and less than 1.5vol%, respectively. The membrane dehydration technology was successfully demonstrated in the commercial production plant as a candidate of the promising next generation technologies.

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