Organisms produce various organic/inorganic hybrid materials, which are called biominerals. They form through the self-organization of organic molecules and inorganic elements under ambient conditions. Biominerals often have highly organized and hierarchical structures from nanometer to macroscopic length scales, resulting in their remarkable physical and chemical properties that cannot be obtained by simple accumulation of their organic and inorganic constituents. These observations motivate us to create novel functional materials exhibiting properties superior to conventional materials--both synthetic and natural. Herein, we introduce recent progress in understanding biomineralization processes at the molecular level and the development of organic/inorganic hybrid materials by these processes. We specifically outline fundamental molecular studies on silica, iron oxide, and calcium carbonate biomineralization and describe material synthesis based on these mechanisms. These approaches allow us to design a variety of advanced hybrid materials with desired morphologies, sizes, compositions, and structures through environmentally friendly synthetic routes using functions of organic molecules.

Fe(3)O(4) synthesized by magnetotactic bacteria and α-Fe(2)O(3) synthesized via a microbial-mineralization-inspired process functioned as catalysts for the controlled cationic polymerization of a vinyl ether.

The effect of carbon dioxide (CO 2 ) in atmospheric gas on the rate of sonochemical oxidation was examined. An ultrasonic irradiation system has two types of effects, namely, physical and chemical effects. In some cases, chemical effects provide a negative performance. To suppress the chemical effect, CO 2 was introduced in a laboratory-scale setup using a syringe or a gas flow system. Sonochemical oxidation was performed at 2.4 MHz (24 W) and 200 kHz (15 W). The rate of oxidation was evaluated by potassium iodide (KI) dosimetry. The rate decreased with the introduction of CO 2 and sonochemical oxidation could not proceed at a mole fraction of CO 2 above 0.3 in the matrix. From the standpoint of practical use, in addition, a sensory test was carried out using 20% ethanol solution in a CO 2 -air atmosphere. No smell change was confirmed by the human sense of smell.

Antibody–enzyme complexes (AECs) are ideal molecular recognition elements for immunosensing applications. One molecule possesses both a binding ability to specific targets and catalytic activity to gain signals, particularly oxidoreductases, which can be integrated into rapid and sensitive electrochemical measurements. The development of AECs using fragment antibodies rather than intact antibodies, such as immunoglobulin G (IgG), has attracted attention for overcoming the ethical and cost issues associated with the production of intact antibodies. Conventionally, chemical conjugation has been used to fabricate AECs; however, controlling stoichiometric conjugation using this method is difficult. To prepare homogeneous AECs, methods based on direct fusion and enzymatic conjugation have been developed, and more convenient methods using Catcher/Tag systems as coupling modules have been reported. In this review, we summarize the methods for fabricating AECs using fragment antibodies developed for sensing applications and discuss the advantages and disadvantages of each method.