Translocation of proteins through biological membranes is a fundamental process in transfer of exported proteins from the position of synthesis to the final destinations. Although many evidences are known about protein translocation across various membranes, it is still unclear how hydrophilic, charged proteins can translate through the hydrophobic core of a phospholipid bilayer. Particularly, there is no answer whether a protein unfolds during the transport process or whether it can translate in a folded state.
In biophysical chemistry on proteins, dynamics of the folding and unfolding pathway of globular proteins have been extensively studied and have established that kinetic intermediate state on folding process might have important roles in the exact folding into a native form. Conformation of intermediate state is compact, has secondary structure similar to the native one but its tertiary structure fluctuates. Such conformation has found in several proteins and is called a “molten globule state”.
The N-F transition of sodium dodecyl sulfate (SDS) -bovine serum albumin (BSA) complex (ADm; m, molar ratio of added SDS to BSA; 0<m<10) were studied by measuring CD-resolved secondary structure, ¹H-1-NMR spectra and cross-relaxation times between irradiated and observed protein protons. From these experimental evidences, the F-form of AD₁₀ may be the molten globule state which has secondary structure similar to the N-form of the complexs with fluctuating tertiary structure. In conclusion, molten globule state not only exists as a kinetic intermediate on protein folding but also is observed in such a lipid-protein complex.

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Techniques of membrane plasma separation consist of microfiltration that is a pressure-driven membrane process for separation of plasma from blood in therapeutic and donor apheresis. Filtration characteristics in plasma separation cannot be explained by the well-known ultrafiltration theory. Elucidation of filtration characteristics and mechanism of fouling is required to develop a highly efficient filter for plasma separation.
In this review, filtration characteristics of a small-sized rotating filter for plasma separation composed of flat polycarbonate and Nylon membranes and a plasma filter composed of microporous glass (MPG) membranes were elucidated. The rotating filter was capable of producing higher wall shear rates caused by the formation of Taylo vortices without significant increases in blood-side pressure drop. The MPG membranes are resistant to chemicals, heating and wear, and these membranes have the advantages of the absence of hemolysis and excellent filtration characteristics because of their limited distribution of pore diameter.

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Peritoneal dialysis is a therapy alternative to conventional hemodialysis for end-stage renal disease patients, which utilizes patients' peritoneal membrane for the treatment. Continuous Ambulatory Peritoneal Dialysis (CAPD) is based on the continuous presence of dialysate in the peritoneal cavity that enables to remove toxic substances with low mass transfer rates. Usually mass transfer rates in peritoneal dialysis were well-explained mathematically with a diffusion-limited model however, experiments in which mass transfer rates had been measured before and after the total evisceration revealed that the peritoneal blood flow rate should play a significant role for mass transfer. A new mass transfer model, which includes both diffusion-limited and blood-flow limited situations as extremes, was proposed and termed Comprehensive Blood flow-Diffusion Model. This model explained all the paradoxical data that had previously been experienced.
Convective mass transfer across the peritoneum is crucial right after the infusion of new dialysate solution. However, diffusion mass transfer should dominate over convective one through out one-whole exchange of the dialysate not to mention for small molecules but even for so-called middle/large molecules.

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Since the beginning of dialysis as a routine therapy for patients with end stage renal failure, the vast majority of patients is treated with cellulosic dialysis membranes (83%). Synthetic polymers as membrane materials, although available since about 20 years, represent only a respectable portion of 17% worldwide. In contrast to stagnating transplantation rates, the dialysis patient population is increasing with yearly 5 to 7%.
When comparing the three major dialysis markets, Japan, Europe and the U. S. A., differences exist between patients' mortality rates. Best survival is achieved in Japan and Europe when set in contrast to data from the U. S.. Results may be explained with specific treatment modalities. Treatment time is longer, dialyser surface area is larger and dialyser re-use is not the dominating practice in these countries with these parameters contributing fundamentally to dialysis adequacy.

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Perfusion culture with cell recycle has been recognized as an effective method to improve the low productivity in animal cell cultivation. Membrane filtration is one of the most effective method for cell recycle, and tangential flow membrane filtration has been used extensively in microbial cultures. In the animal cell cultivation, however, the use of this membrane filtration is still limited, because of the sensitivity of animal cells to hydrodynamic forces. This review paper will introduce the current works for establishment of operating parameters in membrane filtration which maximize permeation flux and minimize membrane fouling while not causing cell damage and lysis.

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We intended to show the possibility of the removal of the Creutzfeldt-Jakob disease (CJD) causative agent by the filtration using the virus removal membrane BMM®, that is, cuprammonium regenerated cellulose hollow fiber. The BMMs with various mean pore size 2r_f ranging between 35 and 75 nm were employed. The supernatant of the centrifuged homogenate obtained from the mouse brains infected with CJD was filtered through BMMs and each filtrate was injected intracerebrally into mice. The concentration of the CJD infectious agent was evaluated through the mean death day caused by CJD after the injection. The dependence of this concentration of the filtrate on 2r_f the change in this concentration of the double filtration, and the change in the concentration of the filtrate from the solution after the treatment of the surfactant “Sarkosyl” was investigated. The infection of CJD was judged from the pathology of spongiform encephalopathy and from the generation of the CJD isoform of Prion Protein (PrPCJD).
The results were summerized as follows : (1) The infectivity of the filtrate decreased when 2r_f decreases, and after the filtration using the BMM with 2r_f value of 35 nm, this infectivity desappeared completely indicating the logarithmic rejection coefficient was more than 6. (2) The double step filtration using two BMMs with 2r_f of 60nm gave about 10% increase in the rejection coefficient comparing with the case of the single step filtration. (3) The treatment of the Sarkosyl made the permeability of the CJD causative agent through the BMM with 2r_f of 40nm increased to 100% and the infectivity increased to about five hundreds times of that of the original solution.

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An improved thermal membrane potential cell was constructed with blocks of poly (vinyl chloride). In the new cell the membrane was used as a ribbon with the two contacts to the external solutions on opposite sides and separated by 0 to 10 mm. Thermal membrane potentials across test anion-exchange membranes Aciplex STA-1 to 5, of which the thickness is about 0.1 mm, were measured using the new cell. The transported entropy of counterions in the membranes was estimated from experimental data for thermal membrane potential, electroosmosis and thermoosmosis. Thermal membrane potentials across STA-2 to 5 were nearly equal to each other regardless of the differences in the water content, the ion-exchange capacity and the DVB content. However, the difference between the mean molar transported entropy of counterions and the partial molar entropy of the ions in the external solutions (s_-s_), which reflects to the stability of counterions in the membrane, decreases roughly with decrease in the water content or with increase in the molality of fixed charges in the membrane. The absolute values of thermal membrane potentials across STA-3 increased in the order of I^->Cl^-≈Br^->IO₃^->F^-≈CH₃COO^- ion forms.

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A new copolyamide hollow fiber RO membrane was designed and developed for the increase of chlorine resistance.
The asymmetric hollow fiber RO membrane showed sufficient RO performance and higher chlorine resistance than conventional composite flat sheet RO membranes made of fully aromatic polyamide.
The new HOLLOSEP (HS-series) module, loaded with the RO membrane is being operated in more than 20 places and these applications are being proved for this module where RO performance and chlorine resistance are beneficial.

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