Elsevier Science BV.Acta Medica Okayama0005-2728180732011Roles of PsbI and PsbM in photosystem II dimer formation and stability studied by deletion mutagenesis and X-ray crystallography319325ENKeisukeKawakamiYasufumiUmenaMasakoIwaiYousukeKawabataMasahikoIkeuchiNobuoKamiyaJian-RenShenPsbM and PsbI are two low molecular weight subunits of photosystem II (PSII), with PsbM being located in the center, and PsbI in the periphery, of the PSII dimer. In order to study the functions of these two subunits from a structural point of view, we crystallized and analyzed the crystal structure of PSII dimers from two mutants lacking either PsbM or PsbI. Our results confirmed the location of these two subunits in the current crystal structure, as well as their absence in the respective mutants. The relative contents of PSII dimers were found to be decreased in both mutants, with a concomitant increase in the amount of PSII monomers, suggesting a destabilization of PSII dimers in both of the mutants. On the other hand, the accumulation level of the overall PSII complexes in the two mutants was similar to that in the wild-type strain. Treatment of purified PSII dimers with lauryldimethylamine N-oxide at an elevated temperature preferentially disintegrated the dimers from the PsbM deletion mutant into monomers and CP43-less monomers, whereas no significant degradation of the dimers was observed from the PsbI deletion mutant. These results indicate that although both PsbM and PsbI are required for the efficient formation and stability of PSII dimers in vivo, they have different roles, namely, PsbM is required directly for the formation of dimers and its absence led to the instability of the dimers accumulated. On the other hand, PsbI is required in the assembly process of PSII dimers in vivo; once the dimers are formed, PsbI was no longer required for its stability.No potential conflict of interest relevant to this article was reported.Elsevier Science SA.Acta Medica Okayama1011-13441041-22011Structure of the catalytic, inorganic core of oxygen-evolving photosystem II at 1.9 Å resolution918ENKeisukeKawakamiYasufumiUmenaNobuoKamiyaJian-RenShenThe catalytic center for photosynthetic water-splitting consists of 4 Mn atoms and 1 Ca atom and is located near the lumenal surface of photosystem II. So far the structure of the Mn(4)Ca-cluster has been studied by a variety of techniques including X-ray spectroscopy and diffraction, and various structural models have been proposed. However, its exact structure is still unknown due to the limited resolution of crystal structures of PSII achieved so far, as well as possible radiation damages that might have occurred. Very recently, we have succeeded in solving the structure of photosystem II at 1.9 angstrom. which yielded a detailed picture of the Mn(4)CaO(5)-cluster for the first time. In the high resolution structure, the Mn(4)CaO(5)-cluster is arranged in a distorted chair form, with a cubane-like structure formed by 3 Mn and 1 Ca, 4 oxygen atoms as the distorted base of the chair, and 1 Mn and 1 oxygen atom outside of the cubane as the back of the chair. In addition, four water molecules were associated with the cluster, among which, two are associated with the terminal Mn atom and two are associated with the Ca atom. Some of these water molecules may therefore serve as the substrates for water-splitting. The high resolution structure of the catalytic center provided a solid basis for elucidation of the mechanism of photosynthetic water splitting. We review here the structural features of the Mn(4)CaO(5)-cluster analyzed at 1.9 angstrom resolution, and compare them with the structures reported previously.No potential conflict of interest relevant to this article was reported.Nature Publishing GroupActa Medica Okayama0028-083647373452011Crystal structure of oxygen-evolving photosystem II at a resolution of 1.9 Å5560ENYasufumiUmenaKeisukeKawakamiJian-RenShenNobuoKamiyaPhotosystem II is the site of photosynthetic water oxidation and contains 20 subunits with a total molecular mass of 350 kDa. The structure of photosystem II has been reported at resolutions from 3.8 to 2.9 angstrom. These resolutions have provided much information on the arrangement of protein subunits and cofactors but are insufficient to reveal the detailed structure of the catalytic centre of water splitting. Here we report the crystal structure of photosystem II at a resolution of 1.9 angstrom. From our electron density map, we located all of the metal atoms of the Mn(4)CaO(5) cluster, together with all of their ligands. We found that five oxygen atoms served as oxo bridges linking the five metal atoms, and that four water molecules were bound to the Mn(4)CaO(5) cluster; some of them may therefore serve as substrates for dioxygen formation. We identified more than 1,300 water molecules in each photosystem II monomer. Some of them formed extensive hydrogen-bonding networks that may serve as channels for protons, water or oxygen molecules. The determination of the high-resolution structure of photosystem II will allow us to analyse and understand its functions in great detail.No potential conflict of interest relevant to this article was reported.Pergamon-Elsevier Science Ltd.Acta Medica Okayama0040-40395122010Palladium- and base-free synthesis of conjugated ynones by cross-coupling reactions of alkynylboronates with acid chlorides mediated by CuCl306308ENYasushiNishiharaDaisukeSaitoEijiInoueYoshiakiOkadaMikihiroMiyazakiYoshiakiInoueKentaroTakagiAlkynylboronates can be employed as a practical and versatile precursor for a variety of pi-conjugated organic compounds. In the presence of Cu(I) salt, cross-coupling reactions of acid chlorides with alkynylboronates giving rise to the corresponding conjugated ynones takes place readily in aprotic polar solvents such as DMI under neutral conditions.No potential conflict of interest relevant to this article was reported.Elsevier Science BV.Acta Medica Okayama0926-33731023-42011Improvement in sulfur desorption of NOX storage and reduction catalysts using a Ba–Ti composite oxide620626ENToshiyukiTanakaIchirouTajimaYuichiKatoYasushiNishiharaHirofumiShinjohA Ba-Ti composite oxide was formed on a NOx storage and reduction catalyst via impregnation of a Ba-Ti precursor solution composed of H(2)O(2) added to a complex prepared using the citric acid method. The structure of the Ba-Ti composite in solution was analyzed by chemical composition analysis and FT-Raman and UV-vis spectroscopy. MM2 calculations were performed to propose its chemical structure. Both Ba and Ti together were found to form a composite molecule in the solution. Furthermore, TEM-EDX and XRD analyses of the Ba-Ti composite oxide on the catalyst prepared by impregnation with the Ba-Ti composite aqueous solution revealed that Ba and Ti in the catalyst were highly dispersed at the nm scale. The formation of the Ba-Ti composite oxide on the NSR catalyst enhanced sulfur desorption efficiency and led to high-performance NO(X) conversion as a NO(X) storage and reduction activity catalyst after desulfation treatment. It was assumed that the existence of nano-scaled Ba compounds combined with Ti was efficient for the inhibition of the sintering of barium sulfate and its facile decomposition. It was found that dispersion of Ba compounds for NO(X) storage materials using a Ba-Ti complex solution is an efficient way to improve the durability of NSR catalysts.No potential conflict of interest relevant to this article was reported.MDPIActa Medica Okayama1420-304916102011Studies on the Synthesis of DMAP Derivatives by Diastereoselective Ugi Reactions88158832ENHirokiMandaiShunsukeIrieKoichiMitsudoSeijiSugaDiastereoselective Ugi reactions of DMAP-based aldehydes with ƒ¿-amino acids and tert-butyl isocyanide were examined. The reactions of 4-(dimethylamino)-2-pyridine-carboxaldehyde with various ƒ¿-amino acids afforded 2-substituted DMAP derivatives with low diastereoselectivity. On the contrary, reactions with 4-(dimethylamino)-3-pyridine-carboxaldehyde delivered 3-substituted DMAP derivatives with moderate to high diastereoselectivity. The combination of ƒ¿-amino acid and DMAP-based aldehyde is thus important to achieve high diastereoselectivity. Kinetic resolution of a secondary alcohol using a chiral DMAP derivative obtained through these reactions was also examined.No potential conflict of interest relevant to this article was reported.Royal Society of ChemistryActa Medica Okayama1359-734546482010Electrochemical generation of silver acetylides from terminal alkynes with a Ag anode and integration into sequential Pd-catalysed coupling with arylboronic acids92569258ENKoichiMitsudoTakuyaShiragaJun-ichiMizukawaSeijiSugaHideoTanakaAn electro-oxidative method for generating silver acetylides from acetylenes with a Ag anode was developed. The reaction could be integrated into a Pd-catalysed electrochemical Sonogashira-type reaction. In the presence of the catalytic amount of Pd(OAc)(2) and 4-BzO-TEMPO, electro-generated silver acetylides reacted immediately with arylboronic acids to afford the corresponding coupling adducts in high yields.No potential conflict of interest relevant to this article was reported.SpringerActa Medica Okayama132010Mechanisms of Acido-Tolerance and Characteristics of Photosystems in an Acidophilic and Thermophilic Red Alga, Cyanidium Caldarium373389ENIsaoEnamiHideyukiAdachiJian-RenShenIn this chapter, we describe the mechanisms of acido-tolerance in an acidophilic- and thermophilic red alga, Cyanidium caldarium. In spite of the extremely acidic environments it inhabits, the intracellular pH of Cyanidium cells is kept neutral by pumping out the protons previously leaked into the cells according to the steep pH gradient. The H+ pump is driven by the plasma membrane ATPase, utilizing intracellular ATP produced by both oxidative phosphorylation and cyclic photophosphorylation via photosystem I. We also describe the characteristics and function of the two photosystems, Photosystem I (PSI) and II (PSII), in Cyanidium caldarium in comparison with those of cyanobacteria, other eukaryotic algae, and higher plants, based on the crystal structures of the two complexes reported so far.No potential conflict of interest relevant to this article was reported.The American Society for Biochemistry and Molecular Biology, Inc.Acta Medica Okayama0021-9258285382010Binding and Functional Properties of Five Extrinsic Proteins in Oxygen-evolving Photosystem II from a Marine Centric Diatom, Chaetoceros gracilis2919129199ENRyoNagaoAkiraMoriguchiTatsuyaTomoAyakoNiikuraSaoriNakajimaTakehiroSuzukiAkinoriOkumuraMasakoIwaiJian-RenShenMasahikoIkeuchiIsaoEnamiOxygen-evolving photosystem II (PSII) isolated from a marine centric diatom, Chaetoceros gracilis, contains a novel extrinsic protein (Psb31) in addition to four red algal type extrinsic proteins of PsbO, PsbQŒ, PsbV, and PsbU. In this study, the five extrinsic proteins were purified from alkaline Tris extracts of the diatom PSII by anion and cation exchange chromatographic columns at different pH values. Reconstitution experiments in various combinations with the purified extrinsic proteins showed that PsbO, PsbQŒ, and Psb31 rebound directly to PSII in the absence of other extrinsic proteins, indicating that these extrinsic proteins have their own binding sites in PSII intrinsic proteins. On the other hand, PsbV and PsbU scarcely rebound to PSII alone, and their effective bindings required the presence of all of the other extrinsic proteins. Interestingly, PSII reconstituted with Psb31 alone considerably restored the oxygen evolving activity in the absence of PsbO, indicating that Psb31 serves as a substitute in part for PsbO in supporting oxygen evolution. A significant difference found between PSIIs reconstituted with Psb31 and with PsbO is that the oxygen evolving activity of the former is scarcely stimulated by Cl| and Ca<sup>2+</sup> ions but that of the latter is largely stimulated by these ions, although rebinding of PsbV and PsbU activated oxygen evolution in the absence of Cl| and Ca<sup>2+</sup> ions in both the former and latter PSIIs. Based on these results, we proposed a model for the association of the five extrinsic proteins with intrinsic proteins in diatom PSII and compared it with those in PSIIs from the other organisms.No potential conflict of interest relevant to this article was reported.Humana PressActa Medica Okayama1064-37456842011Purification and Crystallization of Oxygen-Evolving Photosystem II Core Complex from Thermophilic Cyanobacteria4151ENJian-RenShenKeisukeKawakamiHiroyukiKoikeThis chapter describes the purification and crystallization of oxygen-evolving photosystem II core dimer complex from a thermophilic cyanobacterium Thermosynechococcus vulcanus. Procedures used for purification of photosystem II from the cyanobacterium involves cultivation of cells, isolation of thylakoid membranes, purification of crude and pure photosystem II core complexes by detergent solubilization, followed by differential centrifugation and column chromatography. The purified core dimer particles were successfully used for crystallization, and the methods and conditions used for crystallization are presented. These purification and crystallization procedures can be applied for another thermophilic cyanobacterium T. elongatus.No potential conflict of interest relevant to this article was reported.Elsevier Science BV.Acta Medica Okayama0005-2728179722010Structural and functional studies on Ycf12 (Psb30) and PsbZ-deletion mutants from a thermophilic cyanobacterium278284ENKenjiTakasakaMasakoIwaiYasufumiUmenaKeisukeKawakamiYukariOhmoriMasahikoIkeuchiYuichiroTakahashiNobuoKamiyaJian-RenShenYcf12 (Psb30) and PsbZ are two low molecular weight subunits of photosystem II (PSII), with one and two trans-membrane helices, respectively. In order to study the functions of these two subunits from a structural point of view, we constructed deletion mutants lacking either Ycf12 or PsbZ from Thermosynechococcus elongatus, and purified, crystallized and analyzed the structure of PSII dimer from the two mutants. Our results showed that Ycf12 is located in the periphery of PSII, close to PsbK, PsbZ and PsbJ, and corresponded to the unassigned helix X1 reported previously, in agreement with the recent structure at 2.9 Å resolution (A. Guskov, J. Kern, A. Gabdulkhakov, M. Broser, A. Zouni, W. Saenger, Cyanobacterial photosystem II at 2.9 Å resolution: role of quinones, lipids, channels and chloride, Nat. Struct. Mol. Biol. 16 (2009) 334–342). On the other hand, crystals of PsbZ-deleted PSII showed a remarkably different unit cell constants from those of wild-type PSII, indicating a role of PsbZ in the interactions between PSII dimers within the crystal. This is the first example for a different arrangement of PSII dimers within the cyanobacterial PSII crystals. PSII dimers had a lower oxygen-evolving activity from both mutants than that from the wild type. In consistent with this, the relative content of PSII in the thylakoid membranes was lower in the two mutants than that in the wild type. These results suggested that deletion of both subunits affected the PSII activity, thereby destabilized PSII, leading to a decrease in the PSII content in vivo. While PsbZ was present in PSII purified from the Ycf12-deletion mutant, Ycf12 was present in crude PSII but absent in the finally purified PSII from the PsbZ-deletion mutant, indicating a preferential, stabilizing role of PsbZ for the binding of Ycf12 to PSII. These results were discussed in terms of the PSII crystal structure currently availableNo potential conflict of interest relevant to this article was reported.The American Physical SocietyActa Medica Okayama1098-012181182010Angle-resolved photoemission observation of the superconducting-gap minimum and its relation to the nesting vector in the phonon-mediated superconductor YNi<sub>2</sub>B<sub>2</sub>C180509-1180509-4ENTBabaTYokoyaSTsudaTWatanabeMNoharaHTakagiTOguchiSShinWe have performed ultrahigh-resolution angle-resolved photoemission spectroscopy to directly study the large superconducting (SC) gap anisotropy of YNi<sub>2</sub>B<sub>2</sub>C. We succeed in measuring momentum (k) dependence of SC gap for individual Fermi surface (FS) sheets, which demonstrates complexity of SC gap in a phonon-mediated superconductor. Within measured k regions on FS sheets, we find a pointlike minimum of SC gap, whose k positions can be connected by the known nesting vector. This shows close correlation between the nesting vector and node formation.No potential conflict of interest relevant to this article was reported.The American Physical SocietyActa Medica Okayama1098-012182192010Electronic structure of pristine and K-doped solid picene: Nonrigid band change and its implication for electron-intramolecular-vibration interaction195114-1195114-5ENHOkazakiTWakitaTMuroYKajiXLeeHMitamuraNKawasakiYKubozonoYYamanariTKambeTKatoMHiraiYMuraokaTYokoyaWe use photoemission spectroscopy to study electronic structures of pristine and K-doped solid picene. The valence band spectrum of pristine picene consists of three main features with no state at the Fermi level (E<sub>F</sub>) while that of K-doped picene has three structures similar to those of pristine picene with new states near E<sub>F</sub>, consistent with the semiconductor-metal transition. The K-induced change cannot be explained with a simple rigid-band model of pristine picene but can be interpreted by molecular-orbital calculations considering electron-intramolecular-vibration interaction. Excellent agreement of the K-doped spectrum with the calculations points to importance of electron-intramolecular-vibration interaction in K-doped picene.No potential conflict of interest relevant to this article was reported.The American Physical SocietyActa Medica Okayama1098-012182202010Signature of hidden order and evidence for periodicity modification in URu<sub>2</sub>Si<sub>2</sub>205108-1205108-6ENRikiyaYoshidaYoshiakiNakamuraMasakiFukuiYoshinoriHagaEtsujiYamamotoYoshichikaOnukiMarioOkawaShikShinMasaakiHiraiYujiMuraokaTakayoshiYokoyaThe detail of electronic structures near the Fermi level in URu<sub>2</sub>Si<sub>2</sub> has been investigated employing state-of-art laser angle-resolved photoemission spectroscopy. The observation of a narrow dispersive band near the Fermi level in the ordered state as well as its absence in a Rh-substituted sample strongly suggest that the emergence of the narrow band is a clear signature of the hidden-order transition. The temperature dependence of the narrow band, which appears at the onset of the hidden-order transition, invokes the occurrence of periodicity modification in the ordered state, which is shown for the first time by any spectroscopic probe. We compare our data to other previous studies and discuss possible implications.No potential conflict of interest relevant to this article was reported.International Union of CrystallographyActa Medica Okayama0909-04951862011Development of a soft X-ray angle-resolved photoemission system applicable to 100 µm crystals879884ENTakayukiMuroyukakoKatoTomohiroMatsushitaToyohikoKinoshitaYoshioWatanabeHiroyukiOkazakiTakayoshiYokoyaAkiraSekiyamahigemasaSugaA system for angle-resolved photoemission spectroscopy (ARPES) of small single crystals with sizes down to 100 µm has been developed. Soft X-ray synchrotron radiation with a spot size of `40 µm ~ 65 µm at the sample position is used for the excitation. Using this system an ARPES measurement has been performed on a Si crystal of size 120 µm ~ 100 µm ~ 80 µm. The crystal was properly oriented on a sample stage by measuring the Laue spots. The crystal was cleaved in situ with a microcleaver at 100 K. The cleaved surface was adjusted to the beam spot using an optical microscope. Consequently, clear band dispersions along the Γ-X direction reflecting the bulk electronic states were observed with a photon energy of 879 eV.No potential conflict of interest relevant to this article was reported.ElsevierActa Medica Okayama0368-20481812-32010Angle-resolved photoemission spectroscopy for VO<sub>2</sub> thin films grown on TiO<sub>2</sub> (0 0 1) substrates249251ENYMuraokaKSaekiYYaoTWakitaMHiraiTYokoyaREguchiSShinWe present the results of angle-resolved photoemission spectroscopy (ARPES) measurements of metallic VO<sub>2</sub> thin films. The VO<sub>2</sub> thin films have been grown on TiO<sub>2</sub> (0 0 1) single crystal substrates using pulsed laser deposition. The films exhibit a first-order metal–insulator transition (MIT) at 305 K. In the ARPES spectra of the metallic phase for the films, the O 2p band shows highly dispersive feature in the binding energy range of 3–8 eV along the „C–Z direction. The periodicity of the dispersive band is found to be 2.2 Å<sup>-1</sup> which is almost identical with the periodicity expected from the c-axis length of the VO<sub>2</sub> thin films. The overall feature of the experimental band structure is similar to the band structure calculations, supporting that we have succeeded in observing the dispersive band of the O 2p state in the metallic VO<sub>2</sub> thin film. The present work indicates that the ARPES measurements using epitaxial thin films are promising for determining the band structure of VO<sub>2</sub>.No potential conflict of interest relevant to this article was reported.ElsevierActa Medica Okayama0921-4534470S12010Angle-resolved photoemission study of Si electronic structure: Boron concentration dependenceS641S643ENTakanoriWakitaHiroyukiOkazakiYoshihikoTakanoMasaakiHiraiYujiMuraokaTakayoshiYokoyaThe boron concentration dependence of the Si electronic structure of Si(100)2 ~ 1 surfaces were investigated
by angle-resolved photoemission spectroscopy (ARPES). The ARPES spectra exhibit rigid shifts
toward lower binding energy as the boron concentration increases. The band dispersion was obtained
from fitting procedure, and it is found that the top of the valence band does not exceed the Fermi level
even with a boron concentration 35 times larger than the critical concentration of the metal-insulator
transition.No potential conflict of interest relevant to this article was reported.ElsevierActa Medica Okayama0921-4534470S12010Analysis on photoemission spectrum of superconducting FeSeS389S390ENRikiyaYoshidaTakanoriWakitaHiroyukiOkazakiYoshikazuMizuguchiShunsukeTsudaYoshihikoTakanoHiroyukiTakeyaKazutoHirataYukakoKatoTakayukiMuroMarioOkawaKyokoIshizakaShikShinHisatomoHarimaMasaakiHiraiYujiMuraokaTakayoshiYokoyaIn this paper, we present the result of soft X-ray photoemission spectroscopy and its comparison with the density functional calculation. Although local density approximation seems to be a good starting point for describing the electronic structure of FeSe, the simulated spectrum poorly reproduced the structure around E(B) = 2 eV. This result suggests the necessity of theoretical treatment beyond local density approximation.No potential conflict of interest relevant to this article was reported.Acta Medica Okayama0022-36977252011Ultrahigh-resolution laser photoemission study of URu<sub>2</sub>Si<sub>2</sub> across the hidden-order transition580581ENRikiyaYoshidaYoshiakiNakamuraMasakiFukuiYoshinoriHagaEtsujiYamamotoYoshichikaŌnukiMarioOkawaShikShinMasaakiHiraiYujiMuraokaTakayoshiYokoyaWe have studied the electronic structures of URu<sub>2</sub>Si<sub>2</sub> employing ultrahigh-resolutionlaser angle-resolved photoemission spectroscopy. The change of photoemission spectra is investigated across the hidden-ordertransition, and the emergence of a narrow band is clearly observed near the Fermi level for both (ƒÎ,0) and (ƒÎ,ƒÎ) directions. In addition, it is shown that tuning of light's polarization allows the signal of a hole-like dispersive feature to enhance. These observations prove that laser angle-resolved photoemission spectroscopy is an effective tool for studying the evolution of electronic structures across the hidden-ordertransition in URu<sub>2</sub>Si<sub>2</sub>.No potential conflict of interest relevant to this article was reported.The American Physical SocietyActa Medica Okayama1098-01218612012Comparative photoemission studies on the superconducting gap of the filled skutterudite superconductors LaPt<sub>4</sub>Ge<sub>12</sub> and PrPt<sub>4</sub>Ge<sub>12</sub>014521-1014521-5ENYoshiakiNakamuraHiroyukiOkazakiRikiyaYoshidaTakanoriWakitaHiroyukiTakeyaKazutoHirataMasaakiHiraiYujiMuraokaTakayoshiYokoyaWe performed a comparative study of the superconducting gap in the new filled skutterudite superconductors LaPt<sub>4</sub>Ge<sub>12</sub> and PrPt<sub>4</sub>Ge<sub>12</sub> using high-resolution photoemission spectroscopy. We succeeded in observing spectral changes across Tc that reflect the opening of the superconducting gap in both compounds and also in observing a noticeable difference in their respective superconducting spectral shapes near the Fermi level, pointing toward a more complex superconducting gap structure in PrPt<sub>4</sub>Ge<sub>12</sub>. In addition, we found that the two-gap model is more suitable for describing the superconducting-state spectrum of PrPt<sub>4</sub>Ge<sub>12</sub> than the single-isotropic-gap and single-anisotropic-gap models, which suggests an explanation that multiband effects may possibly induce the anomalous superconducting properties of PrPt<sub>4</sub>Ge<sub>12</sub>.No potential conflict of interest relevant to this article was reported.The Physical Society of JapanActa Medica Okayama0031-901579122010Electronic Structure of the Novel Filled Skutterudite PrPt<sub>4</sub>Ge<sub>12</sub> Superconductor124701-1124701-4ENYoshiakiNakamuraHiroyukiOkazakiRikiyaYoshidaTakanoriWakitaMasaakiHiraiYujiMuraokaHiroyukiTakeyaKazutoHirataHiroshiKumigashiraMasaharuOshimaTakayoshiYokoyaWe have performed soft x-ray photoemission spectroscopy (SXPES) and resonant photoemission spectroscopy (RPES) of the filled skutterudite superconductor PrPt<sub>4</sub>Ge<sub>12</sub> in order to study the electronic structure of valence band and the character of Pr 4f. SXPES of PrPt<sub>4</sub>Ge<sub>12</sub> measured with 1200 eV photon energy, where spectral contribution of Pr 4f is negligible, was found nearly identical with that of LaPt<sub>4</sub>Ge<sub>12</sub>, indicating similarity of Pt–Ge derived electronic states of the two compounds. Good correspondence with band calculations allows us to ascribe the dominant Ge 4p character of the density of states at the Fermi level (E<sub>F</sub>). Pr 3d ¨ 4f RPES shows that, although Pr 4f electrons in PrPt<sub>4</sub>Ge<sub>12</sub> are not as strongly hybridized with conduction electrons near E<sub>F</sub> as in PrFe4P12, there are finite Pr 4f contribution to the states near E<sub>F</sub> in PrPt<sub>4</sub>Ge<sub>12</sub>. These PES results give the information of fundamental electronic structure for understanding the physical properties of the novel filled skutterudite superconductor PrPt<sub>4</sub>Ge<sub>12</sub>.No potential conflict of interest relevant to this article was reported.ElsevierActa Medica Okayama0921-4534470S12010Photoemission study of Ca-intercalated graphite superconductor CaC<sub>6</sub>S637S638ENHiroyukiOkazakiRikiyaYoshidaKeisukeIwaiKengoNoamiTakayukiMuroTetsuyaNakamuraTakanoriWakitaYujiMuraokaMasaakiHiraiFumiakiTomiokaYoshihikoTakanoAsamiTakenakaMasahiroToyodaTamioOguchTakayoshiYokoyaIn this work, we have performed resonant photoemission studies of Ca-intercalated graphite superconductor CaC6. Using photon energy of the Ca 2p-3d threshold, the photoemission intensity of the peak at Fermi energy (E-F) is resonantly enhanced. This result provides spectroscopic evidence for the existence of Ca 3d states at E-F, and strongly supports that Ca 3d state plays a crucial role for the superconductivity of this material with relatively high T-c.No potential conflict of interest relevant to this article was reported.Acta Medica Okayama0022-36977252011Photoemission study of electronic structure evolution across the metal-insulator transition of heavily B-doped diamond582584ENH.OkazakiT.ArakaneK.SugawaraT.SatoT.TakahashiT.WakitaM.HiraiY.MuraokaY.TakanoS.IshiiS.IriyamaH.KawaradaT.YokoyaWe studied the electronic structure evolution of heavily B-doped diamond films across the metal-insulator transition (MIT) using ultraviolet photoemission spectroscopy (UPS). From high-temperature UPS, through which electronic states near the Fermi level (E(F)) up to similar to 5k(B)T can be observed (k(B) is the Boltzmann constant and T the temperature), we observed the carrier concentration dependence of spectral shapes near E(F). Using another carrier concentration dependent UPS, we found that the change in energy position of sp-band of the diamond valence band, which corresponds to the shift of E(F), can be explained by the degenerate semiconductor model, indicating that the diamond valence band is responsible for the metallic states for samples with concentrations above MIT. We discuss a possible electronic structure evolution across MIT.No potential conflict of interest relevant to this article was reported.American Institute of Physics.Acta Medica Okayama0021-897910772010Room temperature ferromagnetic behavior in the hollandite-type titanium oxide073910-1073910-6ENK.NoamiY.MuraokaT.WakitaM.HiraiY.KatoT.MuroY.TamenoriT.YokoyaA hollandite-type K(x)Ti(8)O(16) polycrystalline sample has been prepared and studied by magnetization, resistivity and x-ray photoelectron spectroscopy (XPS). Room temperature ferromagnetic behavior is observed in the magnetic hysteresis measurement. The sample shows a semiconductive temperature dependence in the resistivity measurement. Analysis of the Ti 2p(3/2) core-level XPS spectrum indicates that the titanium ions have a mixed valence of Ti(4+) and Ti(3+). In addition, the valence band spectrum reveals that the 3d electrons tend to localize on Ti(3+) ions in the hollandite-type TiO(2) lattice. Also, analysis of the valence band spectrum shows that the prepared sample is a wide-gap oxide with a band gap of 3.6 eV. These results indicate that the present hollandite-type K(x)Ti(8)O(16) sample can be classified as a TiO(2)-based wide-gap semiconductor with Curie temperature above room temperature. Room temperature ferromagnetism (RTFM) decreases in the sample prepared under a strong reducing gas atmosphere, accompanied with the decrease in the resistivity. The results imply that the localized 3d electrons are responsible for the RTFM of the K(x)Ti(8)O(16) sample.No potential conflict of interest relevant to this article was reported.American Institute of Physics.Acta Medica Okayama0021-897910842010Bulk and surface physical properties of a CrO<sub>2</sub> thin film prepared from a Cr<sub>8</sub>O<sub>21</sub> precursor043916-1043916-4ENK.IwaiY.MuraokaT.WakitaM.HiraiT.YokoyaY.KatoT.MuroY.TamenoriWe have prepared a CrO(2) thin film by chemical vapor deposition from a Cr(8)O(21) precursor and studied the bulk and surface physical properties. The CrO(2) thin film is grown on a TiO(2) (100) substrate by heating of a Cr(8)O(21) precursor and TiO(2) (100) substrate together in a sealed quartz tube. The prepared film is found from x-ray diffraction analysis to be an (100)-oriented single phase. The magnetization and resistivity measurements indicate that the film is a ferromagnetic metal with a Curie temperature of about 400 K. Cr 3s core-level and valence band photoelectron spectroscopy spectra reveal the presence of a metallic CrO(2) in the surface region of the film. Our work indicates that preparation from a Cr(8)O(21) precursor is promising for obtaining a CrO(2) thin film with the metallic surface.No potential conflict of interest relevant to this article was reported.American Institute of Physics.Acta Medica Okayama0021-897910942011Spectroscopic evidence of the formation of (V,Ti)O<sub>2</sub> solid solution in VO<sub>2</sub> thinner films grown on TiO<sub>2</sub>(001) substrates043702-1043702-6ENY.MuraokaK.SaekiR.EguchiT.WakitaM.HiraiT.YokoyaS.ShinWe have prepared VO2 thin films epitaxially grown on TiO2(001) substrates with thickness systematically varied from 2.5 to 13 nm using a pulsed laser deposition method, and studied the transport property and electronic states of the films by means of resistivity and in situ synchrotron photoemission spectroscopy (SRPES). In resistivity measurements, the 13-nm-thick film exhibits a metal-insulator transition at around 290 K on cooling with change of three orders of magnitudes in resistivity. As the film thickness decreases, the metal-insulator transition broadens and the transition temperature increases. Below 4 nm, the films do not show the transition and become insulators. In situ SRPES measurements of near the Fermi level valence band find that the electronic state of the 2.5-nm-thick film is different than that of the temperature-induced insulator phase of VO2 itself although these two states are insulating. Ti 2p core-level photoemission measurements reveal that Ti ions exist near the interface between the films and TiO2 substrates, with a chemical state similar to that in (V,Ti)O-2 solid solution. These results indicate that insulating (V,Ti)O-2 solid solution is formed in the thinner films. We propose a simple growth model of a VO2 thin film on a TiO2(001) substrate. Near the interface, insulating (V,Ti) O-2 solid solution is formed due to the diffusion of Ti ions from the TiO2 substrate into the VO2 film. The concentration of Ti in (V,Ti) O-2 is relatively high near the interface and decreases toward the surface of the film. Beyond a certain film thickness (about 7 nm in the case of the present 13-nm-thick film), the VO2 thin film without any Ti ions starts to grow. Our work suggests that developing a technique for preparing the sharp interface between the VO2 thin films and TiO2 substrates is a key issue to study the physical property of an ultrathin film of "pure" VO2, especially to examine the presence of the novel electronic state called a semi-Dirac point phase predicted by calculations.No potential conflict of interest relevant to this article was reported.American Institute of Physics.Acta Medica Okayama0003-69519882011Multiple phosphorus chemical sites in heavily phosphorus-doped diamond082107-1082107-3ENHiroyukiOkazakiRikiyaYoshidaTakayukiMuroTetsuyaNakamuraTakanoriWakitaYujiMuraokaMasaakiHiraiHiromitsuKatoSatoshiYamasakiYoshihikoTakanoSatoshiIshiiTamioOguchiTakayoshiYokoyaWe have performed high-resolution core level photoemission spectroscopy on a heavily phosphorus (P)-doped diamond film in order to elucidate the chemical sites of doped-phosphorus atoms in diamond. P 2p core level study shows two bulk components, providing spectroscopic evidence for multiple chemical sites of doped-phosphorus atoms. This indicates that only a part of doped-phosphorus atoms contribute to the formation of carriers. From a comparison with band calculations, possible origins for the chemical sites are discussed.No potential conflict of interest relevant to this article was reported.