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71.
Kimura T Takahashi S Akiyama S Uzawa T Ishimori K Morishima I 《Journal of the American Chemical Society》2002,124(39):11596-11597
The helix formation dynamics of poly-L-glutamic acids (PGAs) were observed by the microsecond-resolved Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopies. The helix formation of 34-residue PGA from random coil at pH (or pD for FTIR) 8.0 was initiated by a pH jump to 4.9 using the rapid solution mixer whose mixing dead time is 50 micros. The amide I' line in the time-resolved FTIR spectra exhibited the fast (<100 micros) increase of the total helical content. The time-resolved CD spectra of the same process also showed the fast (<150 micros) formation of short helical segments (5 +/- 1 residues), which was followed by the slower (<1 ms) elongation of the short helices to longer helices (>10 residues). Similar dynamics were observed for the same pH jump of approximately 190-residue PGA, although there were additional steps that made the helix formation of approximately 190-residue PGA more complex. The observed multistep helix formation is likely caused by the strong hydrogen-bonding interactions between the protonated side chains of PGAs. 相似文献
72.
The dielectric solvent effect on HCCH, HCNH and HCNC spin coupling constants in ethane, tetrachloroethane and trans N-methylformamide has been calculated by finite perturbation theory based on the INDO and CNDO/2 approximations incorporating solvaton theory. The available experimental data are interpreted using the calculated variations of spin coupling constants. The effect of dielectric constant on the general form of the Karplus relation is included in the finite perturbation calculations. 相似文献
73.
Shin-ichi Hirano Toshinobu Yogo Wataru Sakamoto Seiji Yamada Tomoyuki Nakamura Tomoe Yamammto Hiroyuki Ukai Kouichi Banno Tomoko Nakafuku Yukari Ando 《Journal of Sol-Gel Science and Technology》2003,26(1-3):35-41
Nano sized crystalline particles/polymer hybrids were synthesized form designed metal-organic precursors. The newly developed method is composed of the synthesis of organic matrix by polymerization and the in situ nucleation and growth of crystalline oxide particles in the organic matrix below 100°C. The design of metal-organic precursor modified with polymerizable ligand and the selection of reaction conditions does influence the size and crystallinity of ceramic particles in organic matrix. The nano-sized magnetic particle/polymer hybrid exhibits the interesting feature of superparamagnetism and quantum size effect. The crystalline particles of BaTiO3/, PbTiO3/, and KNbO3/polymer hybrids behave to be dielectric and show the typical electro-rheological behavior. 相似文献
74.
The reversible transportation of droplets was realized by spatiotemporal control of the wetting gradient. The surface wetting was reversibly regulated by using electrochemical reactions of the ferrocenyl (Fc) alkanethiol monolayer, and the wetting gradient was generated by the application of the in-plane bias voltage to the substrate. The back-and-forth motion of the wetting boundary, where the surface changed from wetting to repulsive, sequentially caused a droplet unidirectional spreading and shrinking on the surface. These unidirectional deformations resulted in the net transport of the droplet in an inchwormlike manner. The droplet moved backward when the direction of the in-plane bias voltage was reversed. 相似文献
75.
This review covers newly isolated simple indole alkaloids, structure determinations, total syntheses and biological activities reported in the literature in 2003. 相似文献
76.
Morita Y Murata T Fukui K Yamada S Sato K Shiomi D Takui T Kitagawa H Yamochi H Saito G Nakasuji K 《The Journal of organic chemistry》2005,70(7):2739-2744
[structure: see text] Novel hydrogen-bonded charge-transfer salts of TCNQ with mono- and diprotonated 4,4'-biimidazolium were synthesized in order to demonstrate the high potential of the 4,4'-biimidazole system in a molecular conductor from the viewpoint of crystal engineering and electronic modulation. Crystal structure analyses of neutral 4,4'-biimidazole and TCNQ salts revealed the formation of two types of hydrogen-bonding modes of the 4,4'-biimidazole moiety depending on the protonated states. Neutral 4,4'-biimidazole possessed a linear chain mode of hydrogen-bonding to construct two-dimensional network. In the TCNQ salt of monoprotonated 4,4'-biimidazolium, the 4,4'-biimidazole moiety formed a dimer by a complementary mode of hydrogen-bonding. In contrast, the salt of diprotonated 4,4'-biimidazolium showed a double linear chain mode of hydrogen-bonding to construct a three-dimensional network. The formation of two types of hydrogen-bonding modes made the difference in the stacking patterns of TCNQ columns and in their transport properties. The TCNQ salt of diprotonated 4,4'-biimidazolium exhibited high electrical conductivity (sigma(rt) = 1.1 x 10(-1) S cm(-1)). 相似文献
77.
Moriya K. Yamada T. Sakai K. Yano S. Baluja S. Matsuo T. Pritz I. Vysochanskii Y. M. 《Journal of Thermal Analysis and Calorimetry》2002,70(2):321-328
Heat capacities of the Pb2xSn2(1-x)P2Se6 crystals (x=0, 0.098, 0.251, 0.402 and 1.0) were measured using an adiabatic calorimeter at temperatures between 10 and 350 K. In the
crystal of x=0, two heat capacity anomalies corresponding to the ferroelectric commensurate - intermediate incommensurate(C-IC) phase
transition temperature T
i, and the incommensurate - paraelectric (IC-N) phase transition temperature T
c, were observed at 193.24±0.10 and 220.07±0.15 K, respectively. The phase transition temperatures decreased with an increase
in Pb2+ concentration. The anomaly at Ti disappeared at x=0.251 in the mixed systems of the Pb2xSn2(1-x)P2Se6. In the crystal of Pb2P2Se6 (x=1.0), no phase transition was observed. The normal heat capacities for the mixed crystals were determined by least squares
fitting of the Debye and Einstein functions to the experimental data. The anomalous heat capacities gave the phase transition
entropies of 8.5 and 1.5 J mol-1 K-1 for x=0. The large transition entropies are consistent with an order-disorder mechanism in the ferroelectric-paraelectric phase
transitions in x=0.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
78.
The solvent extraction of copper(II) with trimethylacetic acid using benzene and 1-octanol as solvents was performed at 25 degrees C and 0.1 mole. dm(-3) ionic strength in the aqueous phase. In contrast to the extraction of copper(II) with a saturated straight-chain carboxylic acid in benzene, the dimeric copper(II) trimethylacetate was observed to dissociate into the monomer, even at a moderately high concentration of copper(II) in the benzene phase. In the system using 1-octanol as a solvent, both the monomeric and dimeric copper(II) species are suggested to be solvated by some 1-octanol molecules. It has been found that the dimerization and adduct formation of copper(II) species in benzene may more effectively enhance the extractability of copper(II) than the solvation by 1-octanol molecules. 相似文献
79.
Isao Karube Tadashi Matsunaga Shuichi Suzuki 《Applied biochemistry and biotechnology》1977,2(2):97-104
A new microbial electrode using immobilizedClostridium butyricum was prepared for biochemical oxygen demand (BOD) estimation of wastewaters. The current of the electrode was decreased with time until a steady state was reached. The steady state current was in all cases attained within 30-40 min at 37°C, and the maximum current output was obtained at 37°C and pH between 6.2 and 7.0. A linear relationship was obtained between the steady state current and BOD. The steady state current values were reproducible within ±7% of the relative error. The BOD of industrial wastewaters can be estimated by using the microbial electrode. Relative error of the BOD estimation of industrial wastewaters was within ± 10%. The current output of the microbial electrode was almost constant for 30 days. 相似文献
80.
A simple one-step conversion of carboxylic acids to urethanes was achieved by diphenyl phosphorazidate (DPPA). The reaction procedure is quite simple, occurring by refluxing an equimolecular mixture of a carboxylic acid, DPPA, and triethylamine in the presence of a hydroxyl component. Aromatic, aliphatic, and heterocyclic carboxylic acids underwent rearrangements in satisfactory yields. As this modified Curtins reaction is much simpler and less laborious than the classical Curtius reaction and proceeds under mild conditions, it may have a broad synthetic utility. 相似文献