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131.
Martina Schfer Ehmke Pohl Karen Schmidt-Bse George M. Sheldrick Rolf Hermann Adriano Malabarba Marino Nebuloni Giancarlo Pelizzi 《Helvetica chimica acta》1996,79(7):1916-1924
The crystal structure of a glycopeptide antibiotic A–40926 aglycone was investigated by X-ray analysis at ?120°. A-40926 crystallises in the orthorhombic space group P212121 with two monomers in the asymmetric unit, a = 21.774(4), b = 28.603(7), c = 29.757(4) Å. ‘Conventional’ direct methods approach failed to solve the structure, but a novel iterative real/reciprocal space procedure was successful. Refinement against 11248 F2 data led to R1 = 13.3% for 6770 F > 4σ (F). The two monomers of A-40926 have similar conformations and are bound by antiparallel H-bonds to form a ‘chain’ structure of connecting dimers. The antibiotic molecule possesses a ‘binding pocket’ for the C-terminal carboxy group of the cell-wall protein, which is consisten with suggestions based on NMR data and the recently reported crystal structure of ureido-balhimycin. In A-40926 the monomers are polymerically linked by H-bonds, quite unlike the tight dimer formation observed in ureido-balhimycin. 相似文献
132.
YanXUE HaiYingYANG YongTanYANG 《中国化学快报》2005,16(1):67-70
A new method was developed for the determination of the size distribution of nano-particles by capillary zone electrophoresis (CZE). Scattering effect of nanoparticles was studied. This method for the determination of size distribution was statistical. 相似文献
133.
134.
3-Diethylamino-5-phenyl-1,2,4-diselenazolium-tetrachloroniccolate(II) — Synthesis and Structure Bis-(N′, N′-diethyl-N-benzoylselenoureato)nickel(II) reacts with diphosgene in benzene to 3-diethylamino-5-phenyl-1,2,4-diselenazolium-tetrachloroniccolate(II). Its structure is confirmed by RKSA and ESCA. The compound consists of cations, which are planar fivemembered rings and of tetrahedral tetrachloroniccolate(II) anions. The complex is isomorphic with 3-diethylamino-5-phenyl-1,2,4-dithiazolium-tetrachloroniccolate(II). 相似文献
135.
Muhammad WT Fox KF Fox A Cotham W Walla M 《Rapid communications in mass spectrometry : RCM》2002,16(24):2278-2285
Single nucleotide polymorphisms (SNPs) and mutations were genotyped for both homozygous and heterozygous PCR products of p53, a tumor suppressor gene, and K-ras, an oncogene, using electrospray ionization (ESI) quadrupole time-of-flight (Q-TOF) mass spectrometry (MS) and ESI-quadrupole MS analysis. Mass accuracy was adequate for both instruments to detect genetic changes in homozygous PCR products, including the most difficult to distinguish (adenine [A] --> thymine [T] transversion). However, for the detection of A --> T shifts (9.0 Da difference) in heterozygous PCR products, the increased resolution of ESI-Q-TOFMS proved essential. Although, greater mass differences in heterozygotes (e.g. cytosine [C] <--> T or guanine [G] <--> A) can be discriminated using ESI-quadrupole MS analysis. 相似文献
136.
富镧混合稀土对ZL101A合金组织和机械性能的影响 总被引:7,自引:2,他引:7
研究了富镧混合稀土对ZL101A合金的铸态、固溶态、T6状态、重熔态的组织和机械性能的影响,提出了混合稀土中入量低压铸造整体车轮合理的热处理状态。 相似文献
137.
聚丙烯纤维辐射接枝进展 总被引:1,自引:0,他引:1
本文对聚丙烯纤维的辐射接枝方法、特征和机理、以及其研究进展和表征进行了扼要综述。 相似文献
138.
139.
Changlun Chen Di Xu Xiaoli Tan Xiangke Wang 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(1):227-233
The fate and transport of toxic metal ions and radionuclides in the environment is generally controlled by sorption reactions.
The extent of sorption of divalent metal cations is controlled by a number of factors including cosorbing or complexing. In
this work, the effects of pH, humic acid HA/Co(II) addition orders, ionic strength, concentration of HA, and foreign cations
on the Co(II) sorption on γ-Al2O3 in the presence of HA were investigated. The sorption isotherms of Co(II) on γ-Al2O3 in the absence and presence HA were also studied and described by using S-type sorption model. The experimental results showed
that the Co(II) sorption is strongly dependent on the pH values, concentration of HA, but independent of HA/Co(II) addition
orders, ionic strength, and foreign cations in the presence of HA under our experimental conditions. The results also indicated
that HA enhanced the Co(II) sorption at low pH, but reduced the Co(II) sorption at high pH. It was hypothesized that the significantly
positive influence of HA at low pH on the Co(II) sorption on γ-Al2O3 was attributed to strong surface binding of HA on γ-Al2O3 and subsequently the formation of ternary surface complexes such as ≡S-OOC-R-(COO−)
x
Co2−x
. Chemi-complexation may be the main mechanism of the Co(II) sorption on γ-Al2O3 in the presence of HA. 相似文献
140.
PhenNO—TTA—乳化剂OP荧光光度法测定微量铕 总被引:3,自引:0,他引:3
研究了Eu(Ⅲ)-PhenNO-TTA-乳化剂OP体系的荧光性质及其用于微量铕的测定。该体系具有良好的分析特性,最低检测限可达7.0×10^-14mol/L. 相似文献