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21.
Motohiko Hikuma Haruo Obana Takeo Yasuda Isao Karube Shuichi Suzuki 《Analytica chimica acta》1980,116(1):61-67
The sensor consists of immobilized E. coli (which contains glutamate decarboxylase) and a carbon dioxide gas-sensor. Continuous introduction of sample solution into a flow system incorporating the sensor gives a potential which increases until a steady state is reached after 5 min. Measurements can also be made with only a 1- or 3-min introduction period with little loss of sensitivity. Calibration plots of mV measurements vs. logarithmic glutamic acid concentration are linear in the range 100–800 mg l-1. The sensor is highly selective, stable and reproducible. It has been applied to the determination of glutamic acid in fermentation broths. 相似文献
22.
A methanol extract from Prunus mume Sieb. Et Zucc. showed a suppressive effect of the SOS-inducing activity on the mutagen 3-amino-1,4-dimethyl-SH-pyrido[4,3-b]indole(Trp-P-1) in the Salmonella typhimurium TA1535/pSK1002 umu test. The methanol extract was re-extracted with hexane, dichloromethane, ethyl acetate, butanol and water. The dichloromethane and ethyl acetate fractions showed suppressive effect. Suppressive compounds were isolated by silica gel column chromatography and identified as trimethyl citrate (1) and dimethyl citrate (2) by GC-MS, IR and 1H and 13C-NMR spectroscopy. Compounds 1 and 2 suppressed 51 and 39% of the SOS-inducing activity at a concentration of 2.0 micromol/mL. 相似文献
23.
Synthesis of two naturally occurring 3-methyl-2,5-dihydro-1-benzoxepin carboxylic acids 总被引:1,自引:0,他引:1
[structures: see text] Two naturally occurring 3-methyl-2,5-dihydro-1-benzoxepin carboxylic acids, 6-hydroxy-3-methyl-8-(phenylethyl)-2,5-dihydro-1-benzoxepin-9-carboxylic acid (radulanin E) (1) and 9-hydroxy-3-methyl-2,5-dihydro-1-benzoxepin-7-carboxylic acid (2), were synthesized using Stille coupling followed by Mitsunobu cyclization. 相似文献
24.
Masakazu Uramoto Kimie Kobinata Kiyoshi Isono Tsutomu Higashijima Tatsuo Miyazawa Ellen E. Jenkins James A. McCloskey 《Tetrahedron》1982,38(11):1599-1608
New chitin synthetase inhibitors, neopolyoxins A, B, and C were isolated from the culture filtrate of Streptomyces cacaoi subsp. asoensis. Their absolute structures have been established on the basis of chemical and spectroscopic evidence. They are structural analogs of the polyoxins. As a nucleobase, neopolyoxin C possesses uracil, while neopolyoxins A and B contain the imidazoline moiety. A ring contraction reaction of pyrimidine nucleoside into imidazoline nucleoside played a key role in the structure determination of the nucleoside moiety. A similar transformation was suggested for the biosynthesis of neopolyoxins A and B. 相似文献
25.
Toshiyuki Yamashita Takeo Fujino Norio Masaki Hiroaki Tagawa 《Journal of solid state chemistry》1981,37(2):133-139
The structural parameters of α- and β-CdUO4 crystals are determined by X-ray powder diffraction technique. α-CdUO4 is rhombohedral and cell parameters are a = 6.233(3) Å and α = 36.12(5)°. β-CdUO4 crystallizes in a C-centered orthorhombic cell with a = 7.023(4), b = 6.849(3), c = 3.514 (2) Å. The space groups are for α-CdUO4 and Cmmm for β-CdUO4. α-CdUO4: 1U in (000), 1Cd in (), 2O(1) in ±(uuu), 2O(2) in ±(vvv); u = 0.113, v = 0.350, Z = 1. β-CdUO4: 2U in (), 2Cd in (), 4O(1) in (), 4O(2) in (); x = 0.159, y = 0.278, Z = 2. β-CdUO4 contains collinear uranyl UO2+2 groups with a UO(1) distance of 1.91 Å, located either along or parallel to the c axis whereas the UO(1) bond length in α-CdUO4 is 1.98 Å which is longer than the usual uranyl bond length. 相似文献
26.
Masakiyo Miyazawa 《Queueing Systems》1994,15(1-4):1-58
We survey the rate conservation law, RCL for short, arising in queues and related stochastic models. RCL was recognized as one of the fundamental principles to get relationships between time and embedded averages such as the extended Little's formulaH=G, but we show that it has other applications. For example, RCL is one of the important techniques for deriving equilibrium equations for stochastic processes. It is shown that the various techniques, including Mecke's formula for a stationary random measure, can be formulated as RCL. For this purpose, we start with a new definition of the rate with respect to a random measure, and generalize RCL by using it. We further introduce the notion of quasi-expectation, which is a certain extension of the ordinary expectation, and derive RCL applicable to the sample average results. It means that the sample average formulas such asH=G can be obtained as the stationary RCL in the quasi-expectation framework. We also survey several extensions of RCL and discuss examples. Throughout the paper, we would like to emphasize how results can be easily obtained by using a simple principle, RCL. 相似文献
27.
Asymmetric monobenzoylation reactions of cyclic meso-1,3- and 1,4-diols were catalyzed by a phosphinite derivative of quinidine to afford the corresponding monobenzoylated diol with good yield and enantioselectivity. [reaction: see text] 相似文献
28.
Copper mediated alkyl-transfer reaction of trialkylaluminum (R3Al) with (E)-4,4-difluoro-5-hydroxyallylic alcohol derivative smoothly proceeded to give the corresponding 2-alkylated 4-fluoro-5-hydroxyhomoallylic alcohol derivative with completely Z and 2,5-syn selective manner. Regio- and stereoselective conversion of the C5-hydroxyl group of the fluoroolefin thus obtained to amino group could be achieved through one-pot mesylation and azidation reaction. 相似文献
29.
Oku T 《Chemical communications (Cambridge, England)》2002,(4):302-303
The three-dimensional potential map of YB56 was obtained by inverse Fourier transformation of three-dimensional phases and amplitudes in three high-resolution images taken along the [100], [110] and [111] directions of YB56 crystals; the size of the imaging region was 14 nm x 14 nm x approximately 4 nm, and the image directly showed the three-dimensional potential map of the crystal, a useful method for three-dimensional structure analysis in nanoscale regions. 相似文献
30.
We estimate the statistical distribution of relative orientations between contacting residues from a database of protein structures and evaluate the potential of mean force for relative orientations between contacting residues. Polar angles and Euler angles are used to specify two degrees of directional freedom and three degrees of rotational freedom for the orientation of one residue relative to another in contacting residues, respectively. A local coordinate system affixed to each residue based only on main chain atoms is defined for fold recognition. The number of contacting residue pairs in the database will severely limit the resolution of the statistical distribution of relative orientations, if it is estimated by dividing space into cells and counting samples observed in each cell. To overcome such problems and to evaluate the fully anisotropic distributions of relative orientations as a function of polar and Euler angles, we choose a method in which the observed distribution is represented as a sum of delta functions each of which represents the observed orientation of a contacting residue, and is evaluated as a series expansion of spherical harmonics functions. The sample size limits the frequencies of modes whose expansion coefficients can be reliably estimated. High frequency modes are statistically less reliable than low frequency modes. Each expansion coefficient is separately corrected for the sample size according to suggestions from a Bayesian statistical analysis. As a result, many expansion terms can be utilized to evaluate orientational distributions. Also, unlike other orientational potentials, the uniform distribution is used for a reference distribution in evaluating a potential of mean force for each type of contacting residue pair from its orientational distribution, so that residue-residue orientations can be fully evaluated. It is shown by using decoy sets that the discrimination power of the orientational potential in fold recognition increases by taking account of the Euler angle dependencies and becomes comparable to that of a simple contact potential, and that the total energy potential taken as a simple sum of contact, orientation, and (phi,psi) potentials performs well to identify the native folds. 相似文献