Dear Chimera support team, I am trying to deposit to the PDB an X-ray crystal structure I solved, and came across with the need to calculate its biological assembly, which is pretty tricky in my case, and so I wondered if Chimera could help me with that. I am working on fibrils made out of repeating units of peptides. The asymmetric unit in my structures usually contains only a monomer, whereas the structure of the fibril is obtained by drawing the copies of this monomer along the fibril axis (potentially there are tens of thousands of those copies), based on the unit cell parameters (the copies are packed within the unit cell). After choosing and drawing an arbitrary number of copies along the axis of fibrillation I would like to get the output of the symmetry operations resulting in this desired representation of the fibril, in order to deposit them as the biological assembly of my structure. I would appreciate if you could advice me to how to obtain those symmetry operations so to define my biomt. Thank you in advance, Einav -- Einav Tayeb-Fligelman, PhD The Landau lab Faculty of Biology Technion, Israel Institute of Technology Haifa, Israel E-mail :einavtf@campus.technion.ac.il Tel at the lab:+972-77-8871964 <+972%2077-887-1964>