I wanted to contact you about the surface representation of a protein. I used to be able to show the surface of our protein and lately I can't show the surface on most multiple subunit proteins because the calculation fails. However, I noticed that on some previously edited structures (the same one as before, except I deleted some of the subunits/ligands) that the surface calculation would work. So, I started deleting lines in the PDB file to see if I could get the surface to start working. Sure enough, when I got to only 1 subunit left, it worked. So after more investigation, I found that if I insert "End" between each of the subunits/ligands in the PDB file then the surface calculation works for the whole structure. I have seen in the release notes of Chimera that some protein surface calculations fail, so having found a way to get mine to work, I thought I would pass it on in case it could shed some light on this surface calculation issue. Or if you have another idea how to "fix" this issue I am having, I would be glad to hear about it. Finally, I wanted to let you know that I thoroughly enjoy using Chimera, it is a great tool. Thanks. Jay