Photosystem II (PSII) drives photo-induced transmembrane electron transfer from the Mn 4 Ca cluster to plastoquinone. It was previously reported that removal of the Mn ions from PSII shifts by ca. +150 mV the redox potential E m of the primary quinone electron acceptor Q A . However, Q A is over 40Å distant from the Mn 4 Ca cluster, and hence the structural rational behind such a long range interaction is still unknown. In this work, we applied an FTIR-spectroelectrochemical technique to study

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... he influence of Mn-depletion on E m of the non-heme iron, located near Q A , to probe the long range interaction in more detail. The result showed that the E m value shifted by +9 mV at most. A possible explanation for the long range phenomena is discussed. Extrinsic proteins in PSII regulate the reactions in the water-oxidizing center (WOC), although its molecular mechanism is unknown. We investigated the effects of the extrinsic proteins on the WOC structure in cyanobacterial PSII using FTIR spectroscopy. S2/S1 FTIR difference spectra exhibited significant changes upon removal of all the extrinsic proteins (PsbO, V, U), whereas spectral features were mostly recovered by rebinding of PsbO. The amide I bands further recovered by rebinding of PsbV, and completely recovered by PsbU. Thus, the three extrinsic proteins affect the structure of WOC in different manners. With the results of a higher plant (PsbO, P, Q) and a red alga (PsbO, V, U, Q'), evolutionary aspects of the functions of extrinsic proteins are discussed. 1P256 光化学系 II における Y Z ラジカルとヒスチジン間の高いプロ トン分極を持つ水素結合:FTIR 法による検出 FTIR evidence for the presence of a strong H-bond with high proton polarizability between the Y Z radical and a His in photosystem II Shin Nakamura, Ryo Nagao, Hanayo Nakanishi, Ryouta Takahashi, Takumi Noguchi (Grad. Sch. Sci., Nagoya Univ.) The redox-active tyrosine Y Z , which is an immediate electron acceptor of the water oxidizing center (WOC) in PSII, is involved in a H-bond network from WOC to the lumen. To clarify the role of Y Z in proton release in the water oxidation mechanism, we investigated the H-bonded structure of Y Z using FTIR spectroscopy. A Y Z · /Y Z FTIR difference spectrum showed a broad positive band around 2800 cm -1 , which was absent in a Y D · /Y D spectrum. DFT calculation on the model complexes of Tyr and His reproduced this vibration as the NH stretch of HisH + H-bonded with a Tyr radical. It was thus concluded that Y Z oxidation produces a strong H-bond with high proton polarizability between Y Z · and protonated D1-His190, which may play a crucial role in proton release during water oxidation. We have studied the role of reactive oxygen species (ROS) from NADPH oxidase in the process of monocytic differentiation of myeloid leukemia PLB-985 cells. Cells were exposed to bioactive 1alpha, 25dihydroxyvitamin D 3 (vitamin D 3 ) and incubated for 3 days for comparison of monocyte differentiation between normal cells and gp91 phox (-) cells (NADPH oxidase knockout). Microscopic observation showed that normal cells differentiated to monocyte. Although knockout cells were not. Expression of Mac-1alpha, one of the monocytic antigen markers, was higher in normal cells than that of in knockout cells. These results suggested that monocyte differentiation induced by vitamin D 3 required ROS generation derived from NADPH oxidase. 1P258 メガヘルツ超音波の抗腫瘍効果 The relationship between cavitation-induced OH radical and cell killing after ultrasound irradiation was investigated in order to properly evaluate MHz ultrasound for therapeutic effects and safety. Irradiation was performed for 10 s at 1.6, 2.4, 5.4 and 7.9 MHz, respectively. Considering cell damage in normal tissue, we examined the proliferation rate of U937 cells. In addition, we examined the induction of apoptosis after irradiation by phosphatidylserine externalization. As a result, cell death was induced by direct burst and necrosis at the frequency and intensity where OH radicals were generated. On the other hand, selective apoptosis was induced in the proper condition that OH radicals were not generated. 1P259 酸化ストレス下でのROS検出 ROS detection in oxidative stress Qualitative and quantitative analysis of reactive oxygen species (ROS) lead to clarify the signal transduction of oxidative stress, which plays an important part in lots of diseases. In this study, we evaluated the method of ROS detection among the chemiluminescence using methyl-6-pmethoxyphenyl-ethynyl-imidazopyrazinone (MPEC), ESR-spin trapping using 5-(2,2-dimethyl-1,3-propoxy cyclophosphoryl)-5-methyl-1-pyrroline N-oxide and aminophenyl fluorescein as a ROS detector. We also reported the efficiency of chemiluminesce in the reactions of MPEC with superoxide, hydroxyl radical, hydrogen peroxide and nitroxide in vitro. Furthermore, each ROS detecting system was compared in PLB-985 cells treated with phorbol ester.