[phenixbb] twin refinement

[subhash bihani]

Hi

i am refining a protein strucutre with space group P61. Intesity statistics
doesnot suggest any twining but refmac and phenix xtriage suggest a twin
operator  with fraction 0.48. when refined with this twin operator R factors
come dowm by 3-5% and also map looks much better. but upon closer inspceion
it seems that maps are heavily biased toward the model in both refmac and
phenix ( I have mutated one lysine to his and it changed the map to cover
his). my question is why twin refinement maps are biased and what are the
ways to overcome this.

my second question is how to decide whether to use twin refinement or not.
is it depends on R factor statistics or we have to check some other
parameters.

thanks in advance


subhash bihani
scientific officer
Bhabha Atomic Research Centre
Trombay-400085
Mumbai(M.S.)
India
Ph. +912594688 (o)
+919322191020

-- 
Subhash Bihani
Scientific Officer
Solid State Physics Division
Bhabha Atomic Research Centre
Trombay, Mumbai-85
Ph. 25594688 (o)
alternate email: subhashbihani at yahoo.co.in
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