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Hi, I'd greatly appreciate advice on how to proceed with trying to solve and refine a structure with nearly perfect merohedral twinning - or is this impossible? The SG is H3; most likely nmol is asu is 4 from Matthews coefficient - but not sure about this. Here are the twinning stats from phenix xtriage ------------------------------------------------------------------ | Operator | type | R obs. | Britton alpha | H alpha | ML alpha | ------------------------------------------------------------------ | h,-h-k,-l | M | 0.038 | 0.452 | 0.468 | 0.478 | ------------------------------------------------------------------ The data is for a novel ligand complex for which we have previously solved structures with different ligands in other space groups - the protein has two domains, and these may have moved compared to other structures. So what should I do? Try and solve by MR using detwinned structure factors? Can Refmac refine the twin fraction, or should I refine against detwinned mtz file? Or ... should we look for additional xtal forms, or try additives to see if we can reduce twinning? Thanks !!!