I have an ARG which has nice density for its guanadinium group on a 2 fold. This is the same conformer from the two copies. The occupancy of this chain is set to 0.5 and a second conformer that does not cross the two fold is provided. There is clearly a repulsion term in phenix refines that moves the quanadinium away from the two fold. Do the atoms of the guanadinum group need to have an occupancy of 0.25? Can I specify no repulsion between these symmetry elements? Best wishes Nick -- Prof Nicholas H. Keep Executive Dean of School of Science Professor of Biomolecular Science Crystallography, Institute for Structural and Molecular Biology, Department of Biological Sciences Birkbeck, University of London, Malet Street, Bloomsbury LONDON WC1E 7HX email [email protected] Telephone 020-7631-6852 (Room G54a Office) 020-7631-6800 (Department Office) Fax 020-7631-6803 If you want to access me in person you have to come to the crystallography entrance and ring me or the department office from the internal phone by the door