This is unlikely to be the result of the method you used to solve the structure. It is probably due to you having some NCS related reflections in the free set and some not. First consider the direction of your 4 fold - could you have a higher symmetry space group?
Eleanor

Vineet Gaur wrote:
Hi all

i m trying to solve a structure at 2.2A using MIR.
i obtained phases using solve. density modification n model building was carried out using phenix. i m solving structure in p212121 space group, with 4 fold NCS. i got almost 80% model built using phenix, rest of the model was built using coot. Right now i am refining the structure at 2.2 Presently Rfree is 36.31% n Rcrys is 35.77%.

Now whatever changes i made, Rfree continues to decrease while Rcryst is more or less stable.

what could be the possible reasons for such a condition. it would be a great help if i can get few tips to overcome this problem.

Thanx in advance
Vineet Gaur

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