[phenixbb] histidine flip in refinement

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 _________________________________ Joel Tyndall, PhD Associate Professor in Medicinal Chemistry National School of Pharmacy University of Otago PO Box 56 Dunedin 9054 New Zealand Skype: jtyndall Ph: +64 3 479 7293