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排序方式: 共有123条查询结果,搜索用时 31 毫秒
81.
82.
Kondo M Nappa J Ronayne KL Stelling AL Tonge PJ Meech SR 《The journal of physical chemistry. B》2006,110(41):20107-20110
Ultrafast time-resolved infrared (TRIR) spectra of flavin adenine dinucleotide (FAD) and the anion of lumiflavin (Lf-) are described. Ground-state recovery and excited-state decay of FAD reveal a common dominant ultrafast relaxation and a minor slower component. The Lf- transient lacks a fast component. No intermediate species are observed, suggesting that the quenching mechanism is internal conversion promoted by interaction of the adenine and isoalloxazine rings in FAD. Modes are assigned, and the potential for extension of the TRIR method to photoactive proteins is discussed. 相似文献
83.
Aoki T Hirano M Takeuchi Y Kobayashi T Yanagida T Ide T 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2010,86(9):920-925
Single channel currents of lysenin were measured using artificial lipid bilayers formed on a glass micropipette tip. The single channel conductance for KCl, NaCl, CaCl(2), and Trimethylammonium-Cl were 474 ± 87, 537 ± 66, 210 ± 14, and 274 ± 10 pS, respectively, while the permeability ratio P(Na)/P(Cl) was 5.8. By adding poly(deoxy adenine) or poly(L-lysine) to one side of the bilayer, channel currents were influenced when membrane voltages were applied to pass the charged molecules through the channel pores. Current inhibition process was concentration-dependent with applied DNA. As the current fluctuations of α-hemolysin channels is often cited as the detector in a molecular sensor, these results suggest that by monitoring channel current changes, the lysenin channel has possibilities to detect interactions between it and certain biomolecules by its current fluctuations. 相似文献
84.
Photochemical welding of silica microspheres to silicone rubber by ArF excimer laser 总被引:1,自引:0,他引:1
Transparent fused silica (SiO2) microspheres 2.5 μm in diameter were photochemically welded to transparent, flexible silicone rubber ([SiO(CH3)2]n) substrate by 193 nm ArF excimer laser induced photochemical modification of silicone into silicon oxide. Single layer of silica microspheres was easily formed on an adhesive silicone rubber before laser irradiation after dropping of silica microspheres dispersed in ethanol and subsequent tape peeling. The welding rate, the percentage of welded microspheres tested by ultrasonic cleaning with ethanol, was examined by varying the single pulse fluence and irradiation time of ArF excimer laser. The welding layer underneath microsphere, silicon oxide, was also found to emit white light of strong intensity under UV light illumination. 相似文献
85.
Takahiro Muraoka Tatsuya Shima Takashi Kajitani Norihisa Hoshino Estelle Morvan Axelle Grlard Erick J. Dufourc Takanori Fukushima Tomoyuki Akutagawa Kota Nabeya Kazushi Kinbara 《化学:亚洲杂志》2019,14(1):141-148
A polymesomorphic thermal phase‐transition of a macrocyclic amphiphile consisting of aromatic groups and oligoethylene glycol (OEG) chains is reported. The macrocyclic amphiphile exists in a highly‐ordered liquid crystal (LC) phase at room temperature. Upon heating, this macrocycle shows phase‐transition from columnar‐lamellar to nematic LC phases followed by crystallization before melting. Spectroscopic studies suggest that the thermally induced crystallization is triggered by a conformational change at the OEG chains. Interestingly, while the macrocycle returns to the columnar‐lamellar phase after cooling from the isotropic liquid, it retains the crystallinity after cooling from the thermally‐induced crystal. Thanks to this bistability, conductance switching was successfully demonstrated. A different macrocyclic amphiphile also shows an analogous phase‐transition behavior, suggesting that this molecular design is universal for developing switchable and memorizable materials, by means of hysteretic phase‐transition processes. 相似文献
86.
Shiina I Hashizume M Yamai YS Oshiumi H Shimazaki T Takasuna YJ Ibuka R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(22):6601-6608
Octalactin A, an antitumor agent containing an eight-membered lactone moiety, has been stereoselectively prepared by means of enantioselective aldol reactions of selected silyl enolates with achiral aldehydes, promoted by a chiral Sn(II) complex. The medium-sized lactone part was effectively constructed by way of a new and rapid mixed-anhydride lactonization using 2-methyl-6-nitrobenzoic anhydride (MNBA) with a catalytic amount of 4-(dimethylamino)pyridine (DMAP) or 4-(dimethylamino)pyridine 1-oxide (DMAPO). The use of only 5 mol % of DMAP or 2 mol % of DMAPO rapidly promoted formation of the medium-sized ring of the octalactin, demonstrating the remarkable efficiency of the new lactonization protocol. 相似文献
87.
Masatsugu Kajitani Hiroshi Hatano Tetsuji Fujita Tetsuyuki Okumachi Hirotaka Nagao Takeo Akiyama Akira Sugimori 《Journal of organometallic chemistry》1992,430(3):C64-C67
The reaction of (η5-cyclopentadienyl)(1,2-benzenedithiolato)cobalt(III) (1) in quadricyclane (Q) at 90°C gives 1:1 adducts of 1 and Q. The main adduct (40% yield) has a unique structure, in which the 5-and 7-positions of norbornene are bonded to Co and S of 1. A mechanism of the formation of the adduct (by the use of deuterium-labeled Q), including a skeletal rearrangement of Q, is proposed. 相似文献
88.
89.
Tohma H Harayama Y Hashizume M Iwata M Kiyono Y Egi M Kita Y 《Journal of the American Chemical Society》2003,125(37):11235-11240
The first stereoselective total synthesis of a potent antitumor alkaloid, discorhabdin A (1), which is a unique sulfur-containing pyrroloiminoquinone alkaloid, is described. The key step in the stereocontrolled total synthesis of 1 involves both a diastereoselective oxidative spirocyclization using a hypervalent iodine(III) reagent and an efficient construction of the labile and highly strained N,S-acetal skeleton. These methodologies provide a breakthrough in the total syntheses of these promising new antitumor agents, discorhabdins and their analogues, which should serve as valuable probes for structure-activity studies. 相似文献
90.
For the analysis of dioxins, polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs) and coplanar polychlorinated biphenyls (Co-PCBs), devising simple and economical methods is important, especially for mass screening of human exposure. Pretreatment of samples, namely the extraction and cleanup methods that are widely used at present, needs to be improved for savings in time, manpower, and solvent consumption. In the present study, we applied solid phase extraction (SPE) using octadecyl (C18) and a blue-chitin column in place of liquid-liquid extraction (LE) and an active-carbon column with serum samples, frequently used for assessment of human exposure. Efficacy of the new pretreatment methods was demonstrated by successful high resolution gas chromatography-high resolution mass spectrometry (HRGC-HRMS) of the major 17 PCDDs/Fs and 12 Co-PCBs that are on the list of WHO/IPCS (1997) hazardous dioxins with toxic equivalent factor (TEF) values. SPE is timesaving and requires less manpower and organic solvent as compared with the LE that is presently widely used. Concerning cleanup with blue-chitin, the amount of toluene applied as eluent could be reduced to 1/3, as compared with the active-carbon case. The combination of SPE and blue-chitin for pretreatment of serum saves time and manpower, is accurate and uses less organic solvent than LE with active carbon cleanup. 相似文献