Hi I am trying fit a ligand (organo phosphate) covalently bonded to residue Serine 250 in my structure. How can I connect this phosphate to Ser-O and during refinement (refmac and CNS), how should I mention in the ligand in the input and how should I number it? I use COOT as graphics. Thanks for suggestion. Sam. _________________________________________________________________ Invite your mail contacts to join your friends list with Windows Live Spaces. It's easy! http://spaces.live.com/spacesapi.aspx?wx_action=create&wx_url=/friends.aspx&mkt=en-us