Browsing by Author "Hsu, I-Jui"

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Anomalous SAXS for the morphology and metal content of a metallothionein in a metal-atom replacement
(2008-01-01)
Jeng, U-Ser
;
Li, Meiyi
;
Hsu, I-Jui
;
Huang, Yu-Shan
;
Wu, YewChung Sermon
Pressure effect on impurity local vibrational mode and phase transitions in n-type iron-doped indium phosphide
(2018-01-19)
Lin, Chih-Ming
;
Hsu, I-Jui
;
Lin, Sin-Cheng
;
Chuang, Yu-Chun
;
Chen, Wei-Ting
The evolution of iron local vibrational mode (Fe LVM) and phase transitions in n-type iron-doped indium phosphide (InP:Fe) were investigated at ambient temperature. In-situ angle-dispersive X-ray diffraction measurements revealed that InP: Fe starts to transform from zinc-blende (ZB) to rock-salt (RS) structure around 8.2(2) GPa and completes around 16.0(2) GPa. The Raman shift of both transverse and longitudinal optical modes increases monotonically with increasing pressure, while their intensities become indiscernible at 11.6(2) GPa, suggesting that the pressure-induced phase transition is accompanied by significant metallization. In contrast, originally absent at ambient pressure, the Raman shift of Fe LVM appears at similar to 420 cm(-1) near 1.2 GPa and exhibits a dome shape behavior with increasing pressure, reaching a maximum value of similar to 440 cm-1 around 5 GPa, with an apparent kink occurring around the ZB-RS transition pressure of similar to 8.5(2) GPa. The Fe K-edge X-ray absorption near edge structure (XANES) confirmed the tetrahedral site occupation of Fe3+ with a crystal field splitting parameter Delta(t)=38k . mole(-1). Our calculations indicate that the energy parameters governing the phase transition are Delta(t)=0.49 and Delta(o) =1.10 kJ . mole(-1),respectively, both are much smaller than Delta(t) = 38 kJ . mole(-1) at ambient.
Resonant X-Ray Scattering and Absorption for the Global and Local Structures of Cu-modified Metallothioneins in Solution
(2009-07-22)
Li, Meiyi
;
Huang, Yu-Shan
;
Jeng, U-Ser
;
Hsu, I-Jui
;
Wu, YewChung Sermon
With Cd and Zn metal ions removed from the native rabbit-liver metallothionein upon unfolding, Cu-modified metallothioneins (Cu-MTs) were obtained during refolding in solutions containing Cu(I) or Cu(II) ions. X-ray absorption near-edge spectroscopic results confirm the respectively assigned oxidation states of the copper ions in Cu(I)-MT and Cu(II)-MT. Global and local structures of the Cu-MTs were subsequently characterized by anomalous small-angle x-ray scattering (ASAXS) and extended x-ray absorption fine structure. Energy-dependent ASAXS results indicate that the morphology of Cu(II)-MT resembles that of the native MT, whereas Cu(I)-MT forms oligomers with a higher copper content. Both dummy-residue simulation and model-shape fitting of the ASAXS data reveal consistently rodlike morphology for Cu(II)-MT. Clearly identified Cu-S, Cu-O, and Cu-Cu contributions in the extended x-ray absorption fine structure analysis indicate that both Cu(I) and Cu(II) ions are bonded with O and S atoms of nearby amino acids in a four-coordination environment, forming metal clusters smaller than metal thiolate clusters in the native MT. It is demonstrated that a combination of resonant x-ray scattering and x-ray absorption can be particularly useful in revealing complementary global and local structures of metalloproteins due to the atom specific characteristics of the two techniques.