To elucidate the heme acquisition system in pathogenic bacteria, we investigated the heme-binding properties of the third NEAT domain of IsdH (IsdH-NEAT3), a receptor for heme located on the surfaces of pathogenic bacterial cells, by using x-ray crystallography, isothermal titration calorimetry, examination of absorbance spectra, mutation analysis, size-exclusion chromatography, and analytical ultracentrifugation. We found the following: 1) IsdH-NEAT3 can bind with multiple heme molecules by two modes; 2) heme was bound at the surface of IsdH-NEAT3; 3) candidate residues proposed from the crystal structure were not essential for binding with heme; and 4) IsdH-NEAT3 was associated into a multimeric heme complex by the addition of excess heme. From these observations, we propose a heme-binding mechanism for IsdH-NEAT3 that involves multimerization and discuss the biological importance of this mechanism.

CPT was successfully incorporated into polymeric micelles with high efficiency and stability by optimizing chemical structures of the inner core segment.

Microstructures of 50 nm thick FePt magnetic thin films deposited on Pt buffer layers with various thicknesses (0–500 nm) grown on a Fe seeded MgO (100) substrate have been studied by transmission electron microscopy to correlate them with magnetic properties. High density of planar defects such as twin and antiphase boundary are present in the FePt films. The twins observed in these films are not the {011} twins which are commonly observed in the bulk FePt magnet, but they are the {111} twins. The density and morphology of these twins drastically change depending on the composition of the FePt thin films as well as the thickness of the Pt buffer layer, while that of the antiphase boundary does not show noticeable changes. In the Pt buffer layer, a high density of dislocations is present in order to reduce the elastic strain due to a large lattice mismatch imposed between the Pt layer and the MgO substrate (about 9%). When the thickness of the Pt buffer layer is increased to 500 nm, the Pt and FePt layers show a polycrystalline microstructure having a grain size ranging from 0.3 to 2.0 μm. The origin of the magnetic hardness is discussed based on these microstructural observation results.

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We have investigated the microstructures and magnetic properties of L10 ordered FePt granular thin films prepared by ion beam sputtering and subsequent annealing. As-deposited FePt–Al–O films are composed of fine spherical FePt particles of ∼2 nm diameter with disordered face-centered-cubic structure. These particles are embedded in the amorphous aluminum oxide matrix with average spacing of ∼1.3 nm, and the film exhibits superparamagnetism. By annealing above 650 °C, the nanoparticles transform to the L10 ordered phase and the grains are coarsened to ∼20 nm, which results in a high coercivity up to 10 kOe. In the films with a high Al content, most of the particles are isolated by the amorphous aluminum oxide matrix, while the grains are interconnected in the films with a low Al content. The changes in magnetic properties are discussed based on the microstructural observation results.

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The microstructure and magnetic property relationship in L10 ordered FePt–Al–O and FePt–Ag granular thin films have been studied. As-sputtered FePt–Al–O films, composed of isolated fine spherical FePt particles of ∼2 nm diameter with a disordered face-centered-cubic (fcc) structure, exhibit superparamagnetism. Annealing above 650 °C induces a transformation from a disordered fcc structure to ordered L10 phase and the films become magnetically hard. The microstructures of these films change greatly depending on the film compositions and annealing conditions, which are correlated with the magnetic properties. It was found that FePt particles smaller than 5 nm do not order at 500 °C, while the continuous FePt film orders perfectly at the same temperature, suggesting that the ordering temperature, Tc, decreases significantly when the particle size becomes less than 5 nm. In the FePt–Ag granular thin film, when the Ag composition is around 50 at. %, high coercivity (∼10 kOe) and fine uniform microstructure are obtained by annealing the films at 550 °C for 1 h. The changes in the magnetic properties of these granular films are discussed based on microstructural observation results.