Protein Crystallographic Methods
Combining Direct Methods with Single Isomorphous Replacement
(SIR) or Single-wavelength Anomalous Diffraction (SAD) Data
2006 progress
Direct-method
SAD phasing at lower resolutions down to 4Å .
Direct-method
SIR phasing based on the partial model from SOLVE/RESOLVE
Fragment extension based on molecular replacemnt without SAD/SIR informatiom
1965 ~ 2005
Background
Solving
a protein structure by using single isomorphous replacement (SIR) or one
wavelength anomalous scattering (OAS) data is important when it is difficult
to prepare multiple isomorphous derivatives and to collect multiwavelength
anomalous diffraction data. However the phase ambiguity intrinsic in SIR
or OAS data obstructs the use of them. The combination of direct methods
with the SIR or the OAS technique may solve the problem and simplify the
process of protein-structure analysis.
MAD and MIR are two major methods of de novo
solution of protein structures. The incorporation of direct methods with MAD or MIR phasing
may lead to better results.