low temp:
- we've had good experiences with early refinement of an ovrall B
in particular when starting from romm temp models or models
with all Bs=20; in once case where Rfree appeared stuck at
about ~42% and sim ann couldn't fix it, refinement of an
overall B shift (grouped b refinement with group = (not hydrogen))
reduced rfree by 4 or 5 % units and after that refinement proceded
smoothly; reason of course: aver B is ~8 A2 for cryo model,
but it was ~15 A2 for the starting model
- since at cryo temp many more waters are ordered you may need
to put in a lot of them (if you have sufficient resolution)
before rfree gets down to 'normal' levels
- we'll have to have a set of atomic resolution structures
refined against cryo data to see if our models need to
be adjusted
--gerard
