Hi Maxine, Somehow I missed your earlier question about how to make cartoon helix tubes straight instead of curved: <https://mail.cgl.ucsf.edu/mailman/archives/list/chimerax-users@cgl.ucsf.edu/...> The short answer is that sorry, ChimeraX currently does not have an option to make them straight. This feature request is in our database as ticket #1242: <https://www.rbvi.ucsf.edu/trac/ChimeraX/ticket/1242> There are some possible workarounds mentioned in the comments on that ticket, namely: ---------------- (1) you could try "define axis" with "perHelix true" and some padding value to show straight cylinders for helices, and then hide the ribbon. The main problem with this workaround is that the other parts of the ribbon do not connect well to the straight cylinders in some places. Example: open 2gbp hide atoms define axis perhelix true padding 2.0 hide helix ribbon Also if you only care about one specific helix, you can hide all of the other straight cylinders and only hide the ribbon for the specific residues in that helix. (2) If you want to modify the Python code in your ChimeraX distribution you can change one line and it will always produce straight helix tubes. The line is 154 in file ChimeraX.app/Contents/lib/python3.9/site-packages/chimerax/atomic/sse.py [** NOTE this is an old comment so the python version is higher now, I believe python3.11 instead of 3.9, and the line number is also different, I believe it's line 166 instead of 154 **] ...on Mac (different location on Windows and Linux, ask if you can't find it) change MIN_CURVE_LENGTH = 13 to MIN_CURVE_LENGTH = 1300 ---------------- I hope this helps, Elaine ----- Elaine C. Meng, Ph.D. UCSF Chimera(X) team Resource for Biocomputing, Visualization, and Informatics Department of Pharmaceutical Chemistry University of California, San Francisco