Developments of hemeprotein systems as biomimetic technologies are reviewed. In particular, it is that i) an artificial blood composed of an oxygen transporter mimicking hemoglobin and myoglobin, ii) a fuel cell composed of an electrocatalyst for reduction of oxygen mimicking cytochrome oxidase, iii) a catalyst of synthesis mimicking cytochrome P-450, iv) a biosensing system mimicking peroxidase and catalase, v) an artificial photosynthesis system mimicking chlorophyll are summarized.

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The development of artificial blood had been proceeded through the development research of the artificial oxygen carrier to substitute for the blood transfusion. We have developed the liposome encapsulated hemoglobin that have superior function for oxygen transport which was close to red blood cell as the biomimetics-technology of red blood cell. The function of oxygen transport was designed that the P 50 value was controlled to 40-50 torr to use the inositol-hexaphosphate as an allosteric effector. The oxygen transporting efficiency of NRC under respiration with 30-50% oxygen was superior to that of human red blood cells (hRBC). NRC showed double efficacy per g-Hb in comparison with hRBC. To mimic the methemoglobin reduction system of red blood cell, the stroma-free hemoglobin (SFH) was prepared with preserving the methemoglobin (metHb) reducing enzymatic activities of red blood cell. We have succeeded that methemoglobin reduction system of red blood cells was mimicked within liposomes.
The development of the artificial oxygen carrier will be able to evolve to aim at the treatment for the stroke and the myocardial infarction as oxygen infusion liquid from the blood substitution in future. So, development of the function design will change from the blood substitution to the therapeutic purposes.

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The breath reaction, which is the four-electron reduction of oxygen to water, should be studied so as to clarify life mechanisms and also produce novel catalysts. In the human body, the breath enzyme, cytochrome oxidase, is the primary agent for four-electron reduction of oxygen to water under atmospheric pressure at mild temperature in ca. pH 7 solution. Structural analysis of this enzyme and mimicking of catalytic reactions has been pursued extensively.
Metalloporphyrins were frequently used as catalysts to promote the reaction. Monomeric metalloporphyrins such as cobalt and iron, permit only two-electron reduction of oxygen to hydrogen peroxide. Multi-nuclear porphyrins such as dimeric porphyrin, tetranuclear ruthenated porphyrin and polymeric metalloporphyrin were used in this study to bring about efficient multi-electron transfer to oxygen for the preferential four-electron reduction of oxygen. Activity only under strong acidic atmosphere has so far been noted.
Oxygen oxidation promoted by 4-electron transfer is essential for many chemical reactions. Synthesis based on 4-electron reduction oxygen and facilitated by a metal catalyst is presently being studied. The catalyst for the 4-electron reduction of oxygen should provide a convenient means for molecular conversion under mild aerobic conditions.

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Aerobic organisms generate reactive oxygen species (ROS) through partial reduction of molecular oxygen to yield O₂^·-, H₂O₂,·OH, NO, and ONOO^-. ROS appear to be involved in various pathologic processes such as tissue injury, inflammatory disorders and ischemic myocardial injury. Numerous anticancer drugs have been found to induce the generation of ROS in cancer cell and the inducement of cancer cell apoptosis by ROS is considered to possibly have therapeutic value.
This paper have reported the possibility of the elimination and generation of ROS by water-soluble cationic metalloporphyrins. For greater clarification of the relationship between metalloporphyrin structure and O₂^·-, novel water-soluble cationic metalloporphyrins were synthesized, as well as a novel water-soluble macromolecular metalloporphyrin for examining in vivo antioxidant effects. The effect of reactive oxygen species induced by water-soluble cationic metalloporphyrins with a high SOD activity on cell death are discussed.

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Photochemical energy conversion using porphyrins and phthalocyanines was conducted as an example of biomimetics for photosynthesis. The photosynthetic system is first briefly explained with attention to importance of porphyrin compounds. An artificial photosynthetic system possesing a photoexcitation center and incorporating oxidation/reduction catalysts and charge mediators was described. Artificial photosynthesis using porphyrins and phthalocyanies was reviewed with particular consideration to photoexcitation centers, photoinduced charge separation, water oxidation catalysts, proton/CO₂ reduction catalysts and charge transport by redox molecules in solid matrixes.

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