Dear Ralf. I just solved the problem with the sugar refinement. Somehow the way the BETA1-4 cif defines the link is in the reverse order to the NAG-ASN cif link (at least to way I was used to do it). In the NAG-ASN cif, residue_selection_1 in the phenix.refine input must be the NAG and residue_selection_2 the ASN, such as I was used to do in CNS. However, the BETA1-4 cifs follows the opposite way: residue_selection_1 must be the first sugar residue (linked through O4) and residue_selection_2 the second sugar (linked through the C1), which is the most distant residue to the Asn. Thanks so much for your help and to all who sent comments and suggestions. Jose M Casasnovas -- Centro Nacional de Biotecnología (lab. B16) CSIC, Campus UAM Darwin 3 28049 Madrid Spain Ph. 34 915854917(8) Fax. 34 915854506 email: [email protected]