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Investigation of Ferroelectric Transition in SrTi18O3 under Hydrostatic Pressure
Masaaki Kurita,Alain Moreac,Jean-Claude Ameline,Masaki Takesada,Mitsuru Itoh,Shinya Koshihara,Tadahiko Ishikawa 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
SrTi18O3 shows a ferroelectric transition at 19.7 K at ambient pressure, and the appearance of new Raman peaks associated with this ferroelectric transition has been reported. This is the rst report of the observation of the change in the Raman spectra under high pressure. The ferroelectric-transition temperature probed by dielectric-property measurements decreases with increasing pressure (P), and the ferroelectric order seems to disappear for the P > 500 bar. Quite parallel behavior has been conrmed for the P dependence of the intensity of the Raman band characteristic of the ferroelectric state.
Kim, Kyung Hwan,Muniyappan, Srinivasan,Oang, Key Young,Kim, Jong Goo,Nozawa, Shunsuke,Sato, Tokushi,Koshihara, Shin-ya,Henning, Robert,Kosheleva, Irina,Ki, Hosung,Kim, Youngmin,Kim, Tae Wu,Kim, Jeongh American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.16
<P/><P>Proteins serve as molecular machines in performing their biological functions, but the detailed structural transitions are difficult to observe in their native aqueous environments in real time. For example, despite extensive studies, the solution-phase structures of the intermediates along the allosteric pathways for the transitions between the relaxed (R) and tense (T) forms have been elusive. In this work, we employed picosecond X-ray solution scattering and novel structural analysis to track the details of the structural dynamics of wild-type homodimeric hemoglobin (HbI) from the clam <I>Scapharca inaequivalvis</I> and its F97Y mutant over a wide time range from 100 ps to 56.2 ms. From kinetic analysis of the measured time-resolved X-ray solution scattering data, we identified three structurally distinct intermediates (I<SUB>1</SUB>, I<SUB>2</SUB>, and I<SUB>3</SUB>) and their kinetic pathways common for both the wild type and the mutant. The data revealed that the singly liganded and unliganded forms of each intermediate share the same structure, providing direct evidence that the ligand photolysis of only a single subunit induces the same structural change as the complete photolysis of both subunits does. In addition, by applying novel structural analysis to the scattering data, we elucidated the detailed structural changes in the protein, including changes in the heme–heme distance, the quaternary rotation angle of subunits, and interfacial water gain/loss. The earliest, R-like I<SUB>1</SUB> intermediate is generated within 100 ps and transforms to the R-like I<SUB>2</SUB> intermediate with a time constant of 3.2 ± 0.2 ns. Subsequently, the late, T-like I<SUB>3</SUB> intermediate is formed via subunit rotation, a decrease in the heme–heme distance, and substantial gain of interfacial water and exhibits ligation-dependent formation kinetics with time constants of 730 ± 120 ns for the fully photolyzed form and 5.6 ± 0.8 μs for the partially photolyzed form. For the mutant, the overall kinetics are accelerated, and the formation of the T-like I<SUB>3</SUB> intermediate involves interfacial water loss (instead of water entry) and lacks the contraction of the heme–heme distance, thus underscoring the dramatic effect of the F97Y mutation. The ability to keep track of the detailed movements of the protein in aqueous solution in real time provides new insights into the protein structural dynamics.</P>
Ichiyanagi, K.,Sato, T.,Nozawa, S.,Kim, K. H.,Lee, J. H.,Choi, J.,Tomita, A.,Ichikawa, H.,Adachi, S.,Ihee, H.,Koshihara, S. International Union of Crystallography 2009 Journal of synchrotron radiation Vol.16 No.3
<▼1><P>A new method of time-resolved solution scattering utilizing X-ray multilayer optics is presented.</P></▼1><▼2><P>100 ps time-resolved X-ray solution-scattering capabilities have been developed using multilayer optics at the beamline NW14A, Photon Factory Advanced Ring, KEK. X-ray pulses with an energy bandwidth of Δ<I>E</I>/<I>E</I> = 1–5% are generated by reflecting X-ray pulses (Δ<I>E</I>/<I>E</I> = 15%) through multilayer optics, made of W/B<SUB>4</SUB>C or depth-graded Ru/C on silicon substrate. This tailor-made wide-bandwidth X-ray pulse provides high-quality solution-scattering data for obtaining photo-induced molecular reaction dynamics. The time-resolved solution scattering of CH<SUB>2</SUB>I<SUB>2</SUB> in methanol is demonstrated as a typical example.</P></▼2>