Hi Liuquing, > For example,first,the resolution is 2.25,R-free is 30,completeness is 90%. > Then I changed resolution to 2.35,R-free became 28.0,completeness is 91%. > When I changed resolution to 2.45,R-free became 27.5,completeness is 92%. > So,when resolution from 2.25 to 2.35,R-free goes down a lot,but > resolution from 2.35 to 2.45,R-free nearly the same,is that meaning > resolution should around 2.35?
This is pretty expected. Just plot R-factor vs resolution for some good amount of structures from PDB. > Should I change resolution during refinement? Only if you have a very *good* reason for doing so. > And is there any good software for refinement? > <http://spaces.live.com/?page=HP> Here are few hints of what's out there: 1) SHELXL (great for refinement at high resolution, comprehensive H atoms handling, twinning; slow since does not use FFT, poor bulk solvent model, no ML targtes); 2) CNS (uses simulated annealing = large convergence radius; good bulk solvent model, twinning, uses various ML targets; high-resolution refinement is not supported, no TLS); 3) REFMAC (TLS, high-resolution refinement, uses ML targets; bulk solvent modeling often unstable); 4) PHENIX (refinement at any resolution is supported: from ultra-high (< 0.9A) to low with sophisticated rigid body refinement (very big convergence radius); robust TLS (never gets "unstable"), robust bulk solvent model (always finds best parameters), simulated annealing, twin refinement, H handing, alternative conformations; torsion angles dynamics is not yet implemented). To find out more about each option -- do Google search. Cheers, Pavel.
