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排序方式: 共有514条查询结果,搜索用时 859 毫秒
91.
Tachikawa T Cui SC Fujitsuka M Majima T 《Physical chemistry chemical physics : PCCP》2012,14(12):4244-4249
Graphene oxide (GO) nanosheets have received a great deal of attention for a wide range of applications from optoelectronic devices to biological sensors. We now report a mechanistic study of the interfacial electron transfer (ET) processes between organic dye molecule, 9-phenyl-2,3,7-trihydroxy-6-fluorone (PF), and nanometre-sized GO sheets using ensemble-averaged and single-molecule spectroscopies. The ET dynamics was characterized by the direct observation of the PF radical cation during the laser flash photolysis, and its reaction rate was determined to be ~10(11) s(-1). The single-molecule fluorescence spectroscopy was utilized to clarify the heterogeneous nature of the interfacial ET within individual composites. Their fluorescence lifetimes and spectra were found to vary from composite to composite, possibly due to the different local structures and molecular interactions. The autocorrelation analysis of fluorescence intensity trajectories also revealed the temporal fluctuation of the ET reactivity. 相似文献
92.
J Choi M Fujitsuka S Tojo T Majima 《Journal of the American Chemical Society》2012,134(32):13430-13435
Pulse radiolysis is a powerful method to realize real-time observation of various redox processes, which induces various structural and functional changes occurring in biological systems. However, its application has been mainly limited to studies of the redox reactions of rather smaller biological systems such as DNA because of an undesired reaction due to various free radicals generated by pulse radiolysis. For application of pulse radiolysis to generate plenty of redox reactions of biological systems, selective redox reactions induced by electron pulses have to be developed. In this study, we report that in the presence of the high concentration of the denaturant, guanidine HCl (GdHCl), the selective reduction of the oxidized cytochrome c (Cyt c) takes place in time scales of a few microseconds by the electron transfer from the guanidine radical that is formed by the fast reaction of e(aq)(-) with GdHCl, consequently leading to folding kinetics of Cyt c. By providing insight into the folding dynamics of Cyt c, we show that the pulse radiolysis technique can be used to track the folding dynamics of various biomolecules in the presence of a denaturant including GdHCl. 相似文献
93.
Yamada S Tokugawa Y Nojiri Y Takamori E 《Chemical communications (Cambridge, England)》2012,48(12):1763-1765
Exposure of 4-azachalcones to HCl gas produced the corresponding HCl salts with a head-to-tail stacked alignment, irradiation of which produced the corresponding syn-HT dimers with high regio- and stereoselectivities, thus showing the effectiveness of the cascade process in crystals. 相似文献
94.
Ohshima T Hayashi Y Agura K Fujii Y Yoshiyama A Mashima K 《Chemical communications (Cambridge, England)》2012,48(44):5434-5436
A simple NaOMe catalyst provides superior accessibility to a wide variety of functionalized amides including peptides through direct amination of esters in an atom-economical and environmentally benign way. 相似文献
95.
We analyzed the photoinactivation of the membrane functions of bacteria and erythrocytes induced by xanthene dyes. The dyes tested were rose bengal, phloxine B, erythrosine B and eosin B. These dyes induced the leakage of K(+) from Staphylococcus aureus cells within minutes of photoirradiation, in the order of rose bengal > phloxine B > erythrosine B > eosin B. The ability of dyes to inhibit respiration was weak, except for rose bengal, and the dyes dissipated the membrane potential in similar time traces with changes in K(+) permeability. The xanthene dyes also induced the leakage of K(+) from bovine erythrocytes upon photoirradiation in the same order as that observed with bacteria. Furthermore, we found that the ability to cause the leakage of K(+) from erythrocytes was associated with dye-induced morphological changes, forming a crenated form from the normal discoid. These results are discussed in connection with the ability of xanthene dyes to generate singlet oxygen and bind to bacterial cells, and further compared with the actions of cationic porphyrins, which induced photoinactivation of bacteria through respiratory inhibition. 相似文献
96.
97.
Tatsuya Oshima Akinori Suetsugu Yoshinari Baba Yuka Shikaze Keisuke Ohto Katsutoshi Inoue 《Journal of membrane science》2008
The present study examined the liquid membrane transport of the cationic protein cytochrome c, using the macrocyclic compound calix[6]arene, which is a carboxylic acid derivative, as a carrier. The transport rate was governed by carrier concentration and the pH gradient between the feed and the receiving phases, as well as the salt concentration in the aqueous phases. Transport of cytochrome c was examined using a series of calix[n]arene carboxylic acid derivatives (n = 4, 6 and 8). Cytochrome c successfully permeated membranes in the presence of the calix[6]arene derivative. Liquid membrane separation of cytochrome c from a mixture of cationic proteins was demonstrated under optimal conditions. Cytochrome c was selectively extracted by the calix[6]arene carboxylic acid derivative and 77% of the extracted cytochrome c was recovered into the receiving phase. In this liquid membrane system, which discriminates between the number of lysine residues on the surface of proteins, cationic proteins with similar molecular weights and pIs were separated with macrocyclic compounds. 相似文献
98.
99.
A Cell‐Targeted Non‐Cytotoxic Fluorescent Nanogel Thermometer Created with an Imidazolium‐Containing Cationic Radical Initiator
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Dr. Seiichi Uchiyama Dr. Toshikazu Tsuji Kyoko Kawamoto Dr. Kentaro Okano Eiko Fukatsu Takahiro Noro Kumiko Ikado Sayuri Yamada Yuka Shibata Dr. Teruyuki Hayashi Dr. Noriko Inada Dr. Masaru Kato Dr. Hideki Koizumi Prof. Hidetoshi Tokuyama 《Angewandte Chemie (International ed. in English)》2018,57(19):5413-5417
A cationic fluorescent nanogel thermometer based on thermo‐responsive N‐isopropylacrylamide and environment‐sensitive benzothiadiazole was developed with a new azo compound bearing imidazolium rings as the first cationic radical initiator. This cationic fluorescent nanogel thermometer showed an excellent ability to enter live mammalian cells in a short incubation period (10 min), a high sensitivity to temperature variations in live cells (temperature resolution of 0.02–0.84 °C in the range 20–40 °C), and remarkable non‐cytotoxicity, which permitted ordinary cell proliferation and even differentiation of primary cultured cells. 相似文献
100.
Hara M Samori S Xichen C Fujitsuka M Majima T 《The Journal of organic chemistry》2005,70(11):4370-4374
Formation and decay of radical cations of trans-stilbene and p-substituted trans-stilbenes (S.+) during the resonant two-photon ionization (TPI) of S in acetonitrile in the presence and absence of O(2) have been studied with laser flash photolysis using a XeCl excimer laser (308 nm, fwhm 25 ns). The transient absorption spectra of S.+ were observed with a peak around 470-490 nm. The formation quantum yield of S.+ (0.06-0.29) increased with decreasing oxidation potential (E(ox)) and increasing fluorescence lifetime (tau(f)) of S, except for trans-4-methoxystilbene which has the lowest E(ox) and longer tau(f) among S. The considerable low yield and fast decay in a few tens of nanoseconds time scale were observed for trans-4-methoxystilbene.+ in the presence of O(2), but not for other S.+ . It is suggested that formation of the ground-state complex between trans-4-methoxystilbene and O(2) and the distonic character of trans-4-methoxystilbene.+ with separation and localization of the positive charge on the oxygen of the p-methoxyl group and an unpaired electron on the beta-olefinic carbon are responsible for the fast reaction of trans-4-methoxystilbene.+ with O(2) or superoxide anion, leading to the considerable low yield and fast decay of trans-4-methoxystilbene.+ . The mechanism based on the transient absorption measurement of S.+ during the TPI is consistent with the relatively high oxidation efficiency of trans-4-methoxystilbene among S based on the product analysis during the photoinduced electron transfer in the presence of a photosensitizer such as 9,10-dicyanoanthracene and O(2) in acetonitrile. 相似文献