Dear all, I have a protein-ligand structure with several chains in the AU. After refinement one of the ligands forms a close contact 1.8A with the protein. For the rest of the protein-ligand chains the same interaction is as expected to 2.7-2.8 A forming an H-bond. I tried to adjust this ligand with coot but everytime I am getting back the same 1.8 A close contact. There is enough density for the ligand and I can even see that it can fit better to distance 2.4-2.5A H-bond with the protein Is there a way to constrain this distance to more than 2A? Should I fix the ligand atom that interacts? Unless I am missing something more fundamental. The ligand cif file is the default in phenix, the data set is a quite decent 2.3A. thanks in advance for any suggestions Nikos -- Dr. Nikos Pinotsis Institute of Structural and Molecular Biology Department of Biological Sciences, 3rd Floor, R313 Birkbeck College Malet Street London WC1E 7HX T: +44 (0)207 631 6827 F: +44 (0)207 631 6803 M: +44 (0)792 384 3593