Variety of quinone and quinoid compounds have been isolated from natural sources. Knowledges on the physiological significances of quinone production in biological systems, are, however, quite limited except those of ubiquinones and plastoquinones in the biological oxidation systems. In the present review, our brief works on the interactions of several naturally occurring, toxic quinones with respriratory chain of mitochondria were described.
Flavoglaucin, a benzohydroquinone derivative from Eurotium chevalieri, exerted an uncoupling effect on oxidative phosphorylation in mitochondria. The uncoupling effect of flavoglaucin, which does not release proton at neutral pH range, was considered to be closely correlated with its strong induction of mitochondrial swelling. Flavoglaucin depressed mitochondrial respiration by directly interacting with the respiratory chain at higher concentrations than those for uncoupling activity. The site of inhibition was identified to be localized mainly at complex I and inferiorly at complex III of the respiratory chain.
Xanthomegnin, a naphthoquinone pigment originally from dermatophytes Trichophyton and Microsporum, was later isolated from several species of saprophytic fungi Aspergillus and Penicillium and was shown to uncouple oxidative phosphorylation. Xanthomegnin exhibited a redox response upon NADH oxidation in submitochondrial particles and in dissolved system, in Which rotenone- and antimycin-inhibitions were no longer observed. It was concluded that xanthomegnin made an electron transport-shunt between complex I and IV in the presence of cytochrome c.
Averufin, an anthraquinone mycotoxin which is a biosynthetic precursor of an extremely potent hepato-carcinogen aflatoxin B₁, was found to be a strong uncoupler of oxidative phosphorylation in mitochondria. At the higher concentrations than those for uncoupling activity, averufin inhibited mitochondrial respiration directly interacting with the respiratory chain at cytochrome bc₁ segment, showing a similarity to the mode of inhibition by antimycin A which is a specific inhibitor to the electron transport between cytochromes b and c₁.

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Simple diffusion, sodium-dependent (active) and-independent (facilitated) transports are generally involved in hexose transport in animal cells. The regulation of facilitated hexose transport has been briefly reviewed. Hexose transport regulation is observed in most cells where the rate of hexose trans-fer is rate limiting for hexose metabolism. Experimental methods used for assay of transport activities and indentification of glucose carrier are very important to deduce any definitive conclusion regarding the regulation of glucose transport. Possible mechanisms of transport regulation might involve 1) control of the carrier synthesis and/or turn over 2) recycling of the carrier 3) modification of the carrier 4) interaction between the carrier and its lipid environment.

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Phospholipids show lyotropic polymorphism. When increasing amount of water is added to dry lecithin, bilayer membrane structure is developed. The colloidal stabilities of membrane, the equilibriums between bilayer and monolayer membranes and the micibilities of lipid components in membrane are investigated for lipids and lipid-polypeptide mixtures. It is found that the water-lipid and lipid-lipid interactions and the thermotropic polymorphisms play important roles in the structure formations of membrane.
Effective polarities and viscosities of close vicinity of amphiphilic probe in lipid membrane and micelle are evaluated on the basis of spectroscopic measurements of the probes. The results clearly show the structural differences between lipid membranes (liposomes) and micelles. Photo-sensitized electron transfers and activations of oxygen are studied in the lipid membrans and micelles, and correlated with the microenvironmental effects (effective polarities and viscosities) in the lipid molecular assemblies.

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There are two kinds of permeation mechanisms through liposome membrane discriminated by the difference of permeation molecules. One is the permeation mechanism concerning the molecular sieving of ions or polar molecules such as K⁺, Na⁺, glucose etc. According to this mechanism, the molecules permeate through the boundary domains between the microclusters composed of molecules either in gel state or in liquid-crystalline state. The other permeation is for water and proton. Proton permeation mechanism is regarded as proton transfer along a network of hydrogen bonded water molecules in the hydrophobioc media of phospholipids. In this article, recent progress in the research on the mechanism are briefly reviewed together with rate studies on permeation of charged materials and related topics.

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How to immobilize bilayer structures in self-standing film and their signal-receptive permeation control of water-soluble substrates are reviewed. There are various method to immobilize lipid bilayers as a self-standing film : (i) casting and drying aqueous despersion of lipid bilayers on a glass plate, (ii) blending lipids with poly (vinylalcohol) or poly (vinylchloride) in a solution and casting on a plate, (iii) coaking lipids in a porous filter membrane, (iv) building-up Langmuir-Blodgett multilayers of lipids on a porous filter, and (v) forming polyion complexes from polyanion and cationic lipids and casting a film from their chloroform solution. Among these methods, the polyion-complex-type bilayer-immobilized film [method (v)] is the most suitable for permeation measurements in aqueous solution. The films is transparent, water-insoluble and physically strong, in which multibilayer structures are well-oriented and piled up parallel to a film plane. Permeation through the bilayer-immobilized film can be reversibly controlled from various outside effects such as temperature (phase transition of bilayers), electric field, and electrochemical redox reactions in lipid bilayers. When the helical structure of poly (L-glutamate) is employed as a counter polyanion, the polyion-complex lipid film shows the stereo-selective permeation of D-, L-triptophan. The lipid bilayer-intercalated clay film can be also prepared when montmorillonite clay is used as counter anioms.

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Water-insoluble PVA-PAA membranes were prepared by casting method from poly (vinyl alcohol), poly (acrylic acid) and formaldehyde. The transport behaviors of transition metal ions through the membrane were investigated under various conditions.
Transition metal ions were actively transported through the PVA-PAA membrane against their concentration gradient from alkaline side (source phase) to acidic side (receiving phase). The high transport ratio for Cu²⁺ was maintained for a long time, and the transport from neutral side to acidic side was not observed. It is interesting to note that the active transport was observed even when pH of receiving phase is in a range of neutrality. The rate of active transport depends strongly on pH of the source phase of metal ions rather than pH of the receiving phase. On the other hand, the transport through PVA membrane was negligibly small.
Although the separation factor is approximately constant for the PAA content in the PVA-PAA membrane, the premselectivity coefficient and the transport rate of metal ions varied with PAA content. When the PAA content in the membrane is about 10 mol%, Cu²⁺ was most selectively transported. For the competitive transport of transition metal ions, the transport selectivity is in following order : Cu²⁺>Ni²⁺=Zn²⁺>Co²⁺.

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