Hi Armando,
I have got a very promising MR solution at 5A resolution. Can I refine this structure? Any hint would be very much appreciated
this is a low resolution indeed, so modeling and refinement is likely to be challenging. All the standard 'low-resolution refinement' advises apply here. Since there are few data (low-res) you need to employ as much 'a priori' known information as possible, in form of restraints or/and constraints. Those typically include: - If NCS is present, use NCS constraints (yes, constraints, not restraints, as at this resolution you are highly unlikely to see data-supported genuine differences between NCS copies!); - if similar homologous models obtained at higher resolution are available -- try using them as reference models; - Use secondary structure restraints. Important: make sure to obtain secondary structure annotation as accurately as possible. - Use Ramachandran plot restraints (to avoid appearing outliers during refinement, not to fix existing ones!); - Avoid stretching your imagination by adding model in the absence of density; - At this resolution refining group B factors (two B per residue) may be a good idea. Let me know if you have any more specific questions! Good luck! Pavel