Please wait a minute...
Chinese Physics, 2003, Vol. 12(8): 890-894    DOI: 10.1088/1009-1963/12/8/313
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES Prev   Next  

Phasing of lysozyme using one-wavelength anomalous scattering of sulphur atoms through the combination of direct methods and density modification

Jiang Fan (江凡), Gu Yuan-Xin (古元新), Zheng Chao-De (郑朝德), Fan Hai-Fu (范海福)
Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
Abstract  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 are 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 are 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.
Keywords:  direct methods      sign probability      anomalous scattering      density modification      sulphur atom phasing  
Received:  24 March 2003      Revised:  29 November 2002      Accepted manuscript online: 
PACS:  87.14.E- (Proteins)  
  61.10.Nz  
  87.64.Bx (Electron, neutron and x-ray diffraction and scattering)  
Fund: Project supported by the National Natural Science Foundation of China (Grant No 30171098).

Cite this article: 

Jiang Fan (江凡), Gu Yuan-Xin (古元新), Zheng Chao-De (郑朝德), Fan Hai-Fu (范海福) Phasing of lysozyme using one-wavelength anomalous scattering of sulphur atoms through the combination of direct methods and density modification 2003 Chinese Physics 12 890

[1] Enhancement of MAD/MIR phasing at low resolution and a new procedure for automatic phase extension
Pu Han(韩普), Yuan-Xin Gu(古元新), Wei Ding(丁玮), Hai-Fu Fan(范海福). Chin. Phys. B, 2019, 28(7): 076108.
[2] New expression of bimodal phase distributions in direct-method phasing of protein single-wavelength anomalous diffraction data
Zhang Tao (张涛), Gu Yuan-Xin (古元新), Zheng Chao-De (郑朝德), Fan Hai-Fu (范海福). Chin. Phys. B, 2010, 19(8): 086102.
[3] Solving a superstructure from two-wavelength x-ray powder diffraction data - a simulation
Chen Jian-Rong (陈建荣), Gu Yuan-Xin (古元新), Fan Hai-Fu (范海福). Chin. Phys. B, 2003, 12(3): 310-314.
[4] Ab-initio determination of the incommensurate modulated structure of Bi-2212 from x-ray powder diffraction data -a simulation
Chen Jian-Rong (陈建荣), Gu Yuan-Xin (古元新), Zheng Chao-De (郑朝德), Fan Hai-Fu (范海福). Chin. Phys. B, 2003, 12(11): 1261-1265.
No Suggested Reading articles found!