Hi David, To summarize for the chimera-users list: 1HLA is an alpha-carbon-only structure, which cannot be shown as a ribbon in Chimera. However, there are many other structures of this protein, several at higher resolution and including all backbone atoms, allowing them to be displayed as ribbons. This Uniprot page has a long list of structures (about 80% of the way down is a "3d structure databases" section): http://www.uniprot.org/uniprot/P01892 The best resolution looks like 1.4 Angstroms, structures 1i4f and 1oga. Both match up with the CA-trace in 1hla quite well. Since they include all backbone atoms, they can be displayed as ribbons. I suggest using 1i4f. 1oga is just as good but has two copies. I hope this helps, Elaine ----- Elaine C. Meng, Ph.D. meng@cgl.ucsf.edu UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco http://www.cgl.ucsf.edu/home/meng/index.html