Browsing by Author "Chen, Tzu-Jung"

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Polymorphic Behavior of Perylene and Its Influences on OFET Performances
(2018-07-19)
Hsieh, Chou-Ting
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Chen, Chin-Yi
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Lin, Heng-Yi
;
Yang, Cheng-Jui
;
Chen, Tzu-Jung
Among the polycyclic aromatic hydrocarbons, although perylene is commercially available and possesses higher solubility and stability than the others, its thin-film structures and organic field-effect transistor (OFET) performances have been rarely explored. To understand its potential as an active material in OFETs, the polymorphic behaviors, packing structures, and OFET characteristics of perylene were carefully examined. The well-oriented crystal arrays of perylene prepared via droplet-pinned crystallization delivered the highest hole mobility among the reported perylene OFETs. Fluorescence microscope, electron diffraction, and lattice modeling results confirm the polymorphic behavior of perylene in the solution-processed crystal arrays and its influences on the OFET performances. The concentration-sensitive and temperature-sensitive polymorphic behavior of perylene make processing conditions crucial in the preparation of pure-phase crystal arrays. The results show the great potential of perylene as an active material in low-cost and high-performance OFETs. Moreover, the knowledge regarding the polymorphic behavior of perylene provides opportunity for the further optimization of perylene-based OFETs.
Structures of Helicobacter pylori Shikimate Kinase Reveal a Selective Inhibitor-Induced-Fit Mechanism
(2012-03-16)
Cheng, Wen-Chi
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Chen, Yen-Fu
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Wang, Hung-Jung
;
Hsu, Kai-Cheng
;
Lin, Shuang-Chih
Shikimate kinase (SK), which catalyzes the specific phosphorylation of the 3-hydroxyl group of shikimic acid in the presence of ATP, is the enzyme in the fifth step of the shikimate pathway for biosynthesis of aromatic amino acids. This pathway is present in bacteria, fungi, and plants but absent in mammals and therefore represents an attractive target pathway for the development of new antimicrobial agents, herbicides, and antiparasitic agents. Here we investigated the detailed structure-activity relationship of SK from Helicobacter pylori (HpSK). Site-directed mutagenesis and isothermal titration calorimetry studies revealed critical conserved residues (D33, F48, R57, R116, and R132) that interact with shikimate and are therefore involved in catalysis. Crystal structures of HpSK center dot SO4, R57A, and HpSK center dot shikimate-3-phosphate center dot ADP show a characteristic three-layer architecture and a conformationally elastic region consisting of F48, R57, R116, and R132, occupied by shikimate. The structure of the inhibitor complex, E114A.162535, was also determined, which revealed a dramatic shift in the elastic LID region and resulted in conformational locking into a distinctive form. These results reveal considerable insight into the active-site chemistry of SKs and a selective inhibitor-induced-fit mechanism.