A novel, to our knowledge, in situ photoirradiation system for solid-state NMR measurements is improved and demonstrated to successfully identify the M-photointermediate of pharaonis phoborhodopsin (ppR or sensory rhodopsin II), that of the complex with transducer (ppR/pHtrII), and T204A mutant embedded in a model membrane. The (13)C NMR signals from [20-(13)C]retinal-ppR and ppR/pHtrII revealed that multiple M-intermediates with 13-cis, 15-anti retinal configuration coexisted under the continuously photoirradiated condition. NMR signals observed from the photoactivated retinal provide insights into the process of photocycle in the ppR/pHtrII complex.

SRI (sensory rhodopsin I) can discriminate multiple colors for the attractant and repellent phototaxis. Studies aimed at revealing the color-dependent mechanism show that SRI is a challenging system not only in photobiology but also in photochemistry. During the photoreaction of SRI, an M-intermediate (attractant) transforms into a P-intermediate (repellent) by absorbing blue light. Consequently, SRI then cycles back to the G-state. The photoreactions were monitored with the (13)C NMR signals of [20-(13)C]retnal-SrSRI using in situ photo-irradiation solid-state NMR spectroscopy. The M-intermediate was trapped at -40 °C by illumination at 520 nm. It was transformed into the P-intermediate by subsequent illumination at 365 nm. These results reveal that the G-state could be directly transformed to the P-intermediate by illumination at 365 nm. Thus, the stationary trapped M- and P-intermediates are responsible for positive and negative phototaxis, respectively.

SRI (sensory rhodopsin I) can discriminate multiple colors for the attractant and repellent phototaxis. Studies aimed at revealing the color-dependent mechanism show that SRI is a challenging system not only in photobiology but also in photochemistry. During the photoreaction of SRI, an Mintermediate (attractant) transforms into a P-intermediate (repellent) by absorbing blue light. Consequently, SRI then cycles back to the G-state. The photoreactions were monitored with the 13 C NMR signals of [20-13 C]retnal-SrSRI using in situ photo-irradiation solid-state NMR spectroscopy. The M-intermediate was trapped at À40 8C by illumination at 520 nm. It was transformed into the P-intermediate by subsequent illumination at 365 nm. These results reveal that the G-state could be directly transformed to the P-intermediate by illumination at 365 nm. Thus, the stationary trapped M-and P-intermediates are responsible for positive and negative phototaxis, respectively.

2P243In situ 光照射固体 NMR による 13-cis, 15-syn バクテリオロ ドプシンの光励起過程における局所構造変化の解析 Thr218 is considered to be functionally important, because this hydrophilic residue is located near the retinal of hydrophobic cytoplasmic (CP) channel. We analyzed the photocycle of various T218 mutants. Wild-type and T218S show 1) the fastest L2 to N transition and 2) the largest dissociation constant of Cl -(K d ) to CP. Thus, Thr or Ser at this position is suitable for the Cl -movement which involves the transfer from the binding site in the extracellular channel followed by the release to the CP space. Pressure dependence of K d yielded the volume differences between N and O (ΔV). Results suggested the water entry at O, which may increase K d . The relationship between K d and ΔV may propose a special coordination of the water molecules with OH group of Thr or Ser. 2P246アセタブラリアロドプシン I の光化学反応 Acetabularia rhodopsin (AR) is a light-driven proton pump found in marine alga, Acetabularia acetabulum. Recently, Jung et al. cloned two homologous AR opsins, and named them ARI and ARII. Previously we reported details of photochemical properties of ARII prepared by the cellfree synthesis. In this study, we focused on the photochemistry of another homologous one, ARI. The photocycle and photo-induced proton transfer of ARI was investigated by the flash photolysis and photoelectrochemical measurement with indium tin-oxide (ITO) electrodes, respectively. On the basis of these results, the expected photocycle and proton transfer scheme of ARI were suggested, and finally discussed compared with ARII or wellknown bacteriorhodopsin. Photochemical reaction in

the FTIR spectra of the photoacuvaUon of Cry DASH from Synechoostis sp [21 and the actiyataon and photorepair by (6 4) photolyasL [3] In present study we apphed FTIR spectroscopy to the phetoiepatr of Cry DASH trom SynLcoLystis sp We confirmed that Cry DASH lrum S)nLcocystts sp ts able to ]epair CPD m smgle tstrand DNA Interestingly it was guggetsted that the oxidized form ofbAD is mvolved m repanr proLess Molecular mechamsm oi photorLpan will be drscussed en the basis ofthe PTIR spcctroscopic results