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1.
郑朝德  吉元新 《物理学报》1983,32(2):280-284
α-氯代桂皮酰另丁胺(反式异构体)的分子式为C13H15ONCl,属正交晶系,空间群为Pbca,a=18.842(0.006)?,b=14.076(0.006)?,c=10.077(0.003)?,晶胞内分子数z=8。用RASA-IIS四圆衍射仪收集衍射强度数据,独立的可观察衍射点929个。用直接法(MULTAN-80)测定其结构。以全部可观察点强度数据用准对角矩阵最小二乘法修正结构参数,R=0.088. 关键词:  相似文献   
2.
本文分析了黄河矿晶体超结构中赝对称性的特点,详述了用于测定黄河矿晶体超结构的直接法。 关键词:  相似文献   
3.
以附加记号法测定异垂盆草甙元的晶体结构时,出现了相位退化问题,由此得到同时混含两个对映体的E图,应用分量关系式成功地将这样的E图复原为只含一个对映体的E图。这一成功表明:使用附加记号法测定非中心对称的晶体结构,当出现相位退化时无需迴避,这就提高了附加记号法的使用效力。  相似文献   
4.
以附加记号法测定异垂盆草甙元的晶体结构时,出现了相位退化问题,由此得到同时混含两个对映体的E图,应用分量关系式成功地将这样的E图复原为只含一个对映体的E图。这一成功表明:使用附加记号法测定非中心对称的晶体结构,当出现相位退化时无需迴避,这就提高了附加记号法的使用效力。  相似文献   
5.
A new method of combining one-wavelength anomalous scattering (OAS) phasing and density modification has been described, in which the improved phases from density modification axe re-introduced into OAS phasing. In this way, the phases could be improved iteratively until convergence. The OAS phasing method is based on the previously established sign-probability formula, which breaks the phase ambiguity in the OAS phasing. The implementation of this method has been available in CCP4 as OASIS. This method, although based on direct-methods, could also incorporate known phases and figures of merit into its sign-probability formula. In the implementation of OASIS, the known phases axe from the positions of the anomalous scatters. In the current method, the known phases are from the density modification. The current method was tested on phasing a lysozyme crystal using anomalous scattering of sulphur atoms with diffraction data collected on an in-house x-ray source. The resulting map was well connected for the backbone atoms and clearly traceable, with an average map correlation coefficient of 0.6622 for the backbone atoms.  相似文献   
6.
张涛  武丽杰  古元新  郑朝德  范海福 《中国物理 B》2010,19(9):96101-096101
There are two kinds of dual-space partial-model extensions which involve the direct-method program OASIS. The first kind, named SAD/SIR iteration, uses SAD/SIR information, while the second kind, named molecular replacement (MR) iteration, does not use that information. In general, the SAD/SIR iteration is more powerful since more experimental information is used. However, in most cases when protein structures are solved with the molecular replacement method, SAD/SIR information is not available. Thus the MR iteration is particularly useful for the completion of models from molecular replacement. The SAD/SIR iteration will be automatically used in OASIS for data sets containing SAD/SIR signals, while the MR iteration will be dedicated to data sets without SAD/SIR signals. The present paper shows that for data containing SAD/SIR signals, a combination of SAD/SIR iteration and MR iteration could lead to significantly better results than that obtained from the SAD/SIR iteration alone.  相似文献   
7.
直接法与单对同晶型置换法或单波长异常散射法相结合,是使直接法参预蛋白质结构分析早期相位推导的一条可能的捷径。 本工作就此进行了比较全面的试验。结果表明,由范海福等人提出的方法可望具有实用的价值。  相似文献   
8.
何尧  古元新  林政炯  郑朝德  范海福 《中国物理》2007,16(10):3022-3028
A new phasing procedure has been proposed for dealing with single isomorphous replacement (SIR) x-ray diffraction data. The procedure combines SOLVE/RESOLVE with the dual-space fragment extension involving OASIS. Two sets of SIR data at 0.28 nm resolution taken from the protein (R)-phycoerythrin (PDB code: 1LIA) were used in the test. For one of the two SIR data sets, a default run of SOLVE/RESOLVE based on the heavy-atom substructure found by SHLEXD led automatically to an interpretable electron density map. OASIS could not effectively improve the result. For the other set of SIR data, SOLVE/RESOLVE resulted in a fragmented model consisting of 454 of the total 668 residues, in which only 29 residues were docked into the sequence. Based on this model, 7 iteration cycles of OASIS-DM- RESOLVE (build only) yielded automatically a model of 547 residues with 133 residues docked into the sequence. The overall-averaged phase error decreased considerably and the quality of electron density map was improved significantly. Two more cycles of iterative OASIS-DM-RESOLVE were carried out, in which the output phases and figures of merit from DM were merged with that from the original run of SOLVE/RESOLVE before they were passed onto RESOLVE (build only). This led automatically to a model containing 452 residues with 173 docked into the sequence. The resultant electron density map is manually traceable. It is concluded that when results of SOLVE/RESOLVE are not sufficiently satisfactory, the combination of SOLVE/RESOLVE and OASIS-DM-RESOLVE (build only) may significantly improve them.  相似文献   
9.
张涛  古元新  郑朝德  范海福 《中国物理 B》2010,19(8):86103-086103
<正>The program OASIS4.0 has been released.Apart from the improved single-wavelength anomalous diffraction (SAD) phasing algorithm described in a separate paper,an important new feature in this version is the automation of the iterative phasing and model-building process in solving protein structures.A new graphical user's interface(GUI) is provided for controlling and real-time monitoring the dual-space iterative process.The GUI is discussed in detail in the present paper.  相似文献   
10.
陈建荣  古元新  郑朝德  范海福 《中国物理》2003,12(11):1261-1265
A set of x-ray powder diffraction data of the high-T_c superconductor Bi_2Sr_2Ca_1Cu_2O_y (Bi-2212) was simulated based on the experimental single-crystal diffraction data by merging together reflections with diffraction angles (2θ) closer to each other than 0.04 degrees. There are three types of overlapping in the powder diffraction data, i.e. (i) overlapping of main reflections; (ii) overlapping of satellite reflections and (iii) overlapping of main and satellite reflections. The third type of overlapping was first separated into main and satellite components according to the ratio between the average intensity of that of types (i) and (ii). Then the overlapped reflections of main reflections and those of the satellites were uniformly partitioned. Heavy-atom sites in the basic/average structure were found using the uniformly decomposed main reflections by the conventional direct method. Phases of the satellites were derived by the multidimensional direct method. The resultant four-dimensional Fourier maps revealed correctly the essential feature of the modulation. No assumption on either the basic structure or the modulation is needed.  相似文献   
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