kind of a weird problem - the R-factors of a refinement using the new
twin refinement in refmac are low, almost suspiciously low:
A good 1.9AA data set, space group H3/R3, many statistics starting
with truncate's cumulative intensity distribution clearly suggest
twinning. The structure (SSGCID target) was solved by MR, very rigid
beta-helix (see 3bxy, very cool fold!), maps nice. I use refmac
5.5.0046 for refinement, with and without the new TWIN flag.
Here my concerns:
Despite 0.3/0.7 twin domains as suggested by various programs and
refined by refmac, the difference of between the Rs of the twinned
refinement and the non-twinned refinement are constantly rather
little: 0.143/0.174 for the twinned case, 0.218/0.275 for the non-
twinned case. This seems rather low to me for a quite high twin
fraction. Plus the R-factors for the twinned case are really low for
a 1.9AA structure. As expected, the maps from the twin treatment are
a bit nicer that for the non-twinned treatment.
Any reasons for concerns or just a very rigid structure that refines
really well or refmac handling twinning really nicely?
Thanks for any input
Seattle / Bainbridge Island WA, USA