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Low-Temperature FTIR Spectroscopy of Bacteriorhodopsin and Phoborhodopsin
Kandori, Hideki,Furutani, Yuji,Shimono, Kazumi,Iwamoto, Masayuki,Sudo, Yuki,Shichida, Yoshinori,Kamo, Naoki Korean Society of Photoscience 2002 Journal of Photosciences Vol.9 No.2
Archaeal rhodopsins possess retinal molecule as their chromophores, and their light-energy and light-signal conversions are triggered by all-trans to 13-cis isomerization of the retinal chromophore. Relaxation through structural changes of protein then leads to functional processes, proton pump in bacteriorhodopsin (bR) and transducer activation in phoborhodopsin (pR). It is known that sensory rhodopsins can pump protons in the absence of their transducers. Thus, there should be common and specific features in their protein structural changes for function. In this paper, our r ecent studies on pR from Natronobacterium pharaonis (ppR) by means of low-temperature Fourier-transform infrared (FTIR) spectroscopy are compared with those of bR. In particular, protein structural changes upon retinal photoisomerization are studied. Comparative investigation of ppR and bR revealed the similar structures of the polyene chain of the chromophore and water-containing hydrogen-bonding network, whereas the structural changes upon photoisomerization were more extended in ppR than in bR. Extended protein structural changes were clearly shown by the assignment of the C=O stretch of Asnl05. FTIR studies of a ppR mutant with the same retinal binding site as in bR revealed that the Schiff base region is important to determine their colors.
Real-space Imaging of Ferroelectric and Structural Antiphase Domains in Hexagonal YMnO<sub>3</sub>
Keisuke Kobayashi,Hideki Kamo,Kosuke Kurushima,Yoichi Horibe,정상욱,Yoshihiko Togawa,Shigeo Mori 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.7
A high-angle annular-dark-field (HAADF) imaging technique was applied to the investigation of domain wall structures in the ferroelectric phase of hexagonal manganites, YMnO<sub>3</sub>, on an atomic scale. The displacements of the Y<sup>3+</sup> ions along the [001] direction can be clearly visualized. The ferroelectric dipole moments are revealed to be caused by the opposite and unequal displacements of Y<sup>3+</sup> ions. Two types of domain walls should be identified in the ferroelectric domain structures. One is charged longitudinal domain walls with head-to-head or tail-to-tail configurations and the other is non-charged transverse domain walls with head-to-tail configurations. In addition, the ferroelectric and the structural antiphase domains in YMnO<sub>3</sub> change into fragmentary domains because of substitution of Ti<sup>4+</sup> for Mn<sup>3+</sup>, and ferroelectric nanodomains with sizes of 10 - 20 nm are found in the x = 0.30 compound.
Effect of Asp193 on Proton Affinity of the Schiff Base in pharaonis phoborhodopsin
Iwamoto, Masayuki,Furutani, Yuji,Sudo, Yuki,Shimono, Kazumi,Kandori, Hideki,Kamo, Naoki Korean Society of Photoscience 2002 Journal of Photosciences Vol.9 No.2
Spectroscopic titration of D 193N and D 193E mutants of pharaonis phoborhodopsin (ppR) were performed to evaluate the pK$_{a}$ of the Schiff base Asp 193 corresponds to Glu204 of bacteriorhodopsin (bR). The pK$_{a}$ of the Schiff base (SBH$^{+}$) of D193N was 10.1~10.0 (at XH$^{+}$) and 11.4~11.6 (at X) depending on the protonation state of a certain residue (designated by X) and independent on CI$^{[-10]}$ , while those of the wild-type and D193E were> 12. pK$_{a}$ of XH$^{+}$ were; 11.8~11.2 at the state of SB, 10.5 at SBH$^{+}$ state in the presence of CI$^{[-10]}$ , and 9.6 at SBH$^{+}$ without CI$^{[-10]}$ These imply the presence of a long-range interaction in the extracellular channel.r channel.