Hi Joel,

as was suggested main.nqh_flips=False should disable this.

However I'm puzzled about this. NQH flips functionality is designed to flip these residues such that the clashes are minimized and plausible H-bonding is achieved. So I wonder why it is not working in your case?

Would it be possible to send me input files (off list) so that I can reproduce this and investigate. Also please indicate HIS in question.

Thanks,
Pavel

On 7/21/15 02:07, Joel Tyndall wrote:

Hi all,

We are trying to optimise a histidine interaction where NE2 would ideally make a hydrogen bond with an adjacent tyrosine hydroxyl. The starting point contains the hydrogen bond. However upon refinement the ring flips (chi2 x 180 degrees) to place the CE1 adjacent to the tyrosine hydroxyl.

Is it possible to stop this as I see no reason why phenix.refine would want to do this

Regards

Joel