[phenixbb] Twin fraction in phenix refine

[Pietro Roversi]

Dear all,
                  phenix.xtriage estimates a twin fraction
of between 24 and 30% but then when I start the refinement
I get 47-49%. In CNS if I fix the twin fraction in a series
of refinements the Rfactors jump from 44% (twin fraction 0)
to 37% (from 25% to 49%, only marginal improvement
upon going from alpha=25% to 49%). Questions:

1. Is the refinement of alpha dependent on the model?
2. I am tempted to work with the 30% that xtriage estimates
but do not know how: is there a way to fix alpha?

Thanks

Pietro
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Pietro Roversi
EP Abraham Fellow in Biochemistry - Lincoln College - Oxford
Sir William Dunn School of Pathology, Oxford University
South Parks Road, Oxford OX1 3RE, England UK
Tel. 0044-1865-275385
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