著者 Morimoto, Naoki| Suzuki, Hideyuki| Takeuchi, Yasuo| Kawaguchi, Shogo| Kunisu, Masahiro| Bielawski, Christopher W.| Nishina, Yuta|
抄録 Graphite oxide (GO) and its constituent layers (i.e., graphene oxide) display a broad range of functional groups and, as such, have attracted significant attention for use in numerous applications. GO is commonly prepared using the “Hummers method” or a variant thereof in which graphite is treated with KMnO4 and various additives in H2SO4. Despite its omnipresence, the underlying chemistry of such oxidation reactions is not well understood and typically affords results that are irreproducible and, in some cases, unsafe. To overcome these limitations, the oxidation of graphite under Hummers-type conditions was monitored over time using in situ X-ray diffraction and in situ X-ray absorption near edge structure analyses with synchrotron radiation. In conjunction with other atomic absorption spectroscopy, UV–vis spectroscopy and elemental analysis measurements, the underlying mechanism of the oxidation reaction was elucidated, and the reaction conditions were optimized. Ultimately, the methodology for reproducibly preparing GO on large scales using only graphite, H2SO4, and KMnO4 was developed and successfully adapted for use in continuous flow systems.
備考 2018年3月公開予定
発行日 2017-03-02
出版物タイトル Chemistry of Materials
29巻
5号
出版者 American Chemical Society
開始ページ 2150
終了ページ 2156
ISSN 15205002
NCID AA12096771
資料タイプ 学術雑誌論文
言語 English
OAI-PMH Set 岡山大学
著作権者 Copyright © 2017 American Chemical Society
論文のバージョン author
Web of Sience KeyUT 000396639400027
関連URL https://doi.org/10.1021/acs.chemmater.6b04807
著者 Niho, Akiko| Yoshizawa, Susumu| Tsukamoto, Takashi| Kurihara, Marie| Tahara, Shinya| Nakajima, Yu| Mizuno, Misao| Kuramochi, Hikaru| Tahara, Tahei| Mizutani, Yasuhisa| Sudo, Yuki|
抄録 In organisms, ion transporters play essential roles in the generation and dissipation of ion gradients across cell membranes. Microbial rhodopsins selectively transport cognate ions using solar energy, in which the substrate ions identified to date have been confined to monovalent ions such as H+, Na+, and Cl-. Here we report a novel rhodopsin from the cyanobacterium Synechocystis sp. PCC 7509, which inwardly transports a polyatomic divalent sulfate ion, SO42-, with changes of its spectroscopic properties in both unphotolyzed and photolyzed states. Upon illumination, cells expressing the novel rhodopsin, named Synechocystis halorhodopsin (SyHR), showed alkalization of the medium only in the presence of Cl- or SO42-. That alkalization signal was enhanced by addition of a protonophore, indicating an inward transport of Cl- and SO42- with a subsequent secondary inward H+ movement across the membrane. The anion binding to SyHR was suggested by absorption spectral shifts from 542 to 536 nm for Cl- and from 542 to 556 nm for SO42-, and the affinities of Cl- and SO42- were estimated as 0.112 and 5.81 mM, respectively. We then performed time-resolved spectroscopic measurements ranging from femtosecond to millisecond time domains to elucidate the structure and structural changes of SyHR during the photoreaction. Based on the results, we propose a photocycle model for SyHR in the absence or presence of substrate ions with the timing of their uptake and release. Thus, we demonstrate SyHR as the first light-driven polyatomic divalent anion (SO42-) transporter and report its spectroscopic characteristics.
備考 This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of the American Chemical Society, copyright © American Chemical Society after peer review and technical editing by the publisher. 2018年4月公開予定
発行日 2017-03-29
出版物タイトル Journal of the American Chemical Society
139巻
12号
出版者 American Chemical Society
開始ページ 4376
終了ページ 4389
ISSN 00027863
NCID AA00692602
資料タイプ 学術雑誌論文
言語 English
OAI-PMH Set 岡山大学
論文のバージョン author
PubMed ID 28257611
Web of Sience KeyUT 000398247100034
関連URL https://doi.org/10.1021/jacs.6b12139