Hi Elaine Sorry, I should have been clearer. This was my command: rna model /Users/dmathur/Documents/gapB-sfGFP-mRNA.fasta path #0 and rna model /Users/dmathur/Documents/gapB-sfGFP-mRNA.fasta path #0 start 40 length 8 Both return the same error. -- Divita Mathur, PhD Research Assistant Professor George Mason University & Center for Bio/Molecular Science and Engineering Naval Research Laboratory (202) 767-0687 (Office) On 4/5/21, 8:26 PM, "Elaine Meng" <meng@cgl.ucsf.edu> wrote: Hi Divita, Is “rna model sequence #0” actually the command you gave? In the command usage, the word "sequence" (shown in italics) is supposed to be pathname of the file with the sequence in it (not literally the word "sequence"), and you are also required to either give the "path" option or the "pairs" option. You cannot omit both. "rna model" help <https://www.rbvi.ucsf.edu/chimera/docs/UsersGuide/midas/rna.html#model> how to read command usage in help pages <https://www.rbvi.ucsf.edu/chimera/docs/UsersGuide/midas/rna.html#model> So if you had the path markers as #0 then your command could be something like rna model /Users/divita/Documents/blahblah.fasta path #0 (of course, change the pathname as appropriate for the detailed location and filename of your fasta file.) I hope this helps, Elaine ----- Elaine C. Meng, Ph.D. UCSF Chimera(X) team Department of Pharmaceutical Chemistry University of California, San Francisco > On Apr 5, 2021, at 9:38 AM, Divita Mathur, Contractor Code 6910, FN <divita.mathur.ctr.in@nrl.navy.mil> wrote: > > Hello Chimera community > I am trying to run the “rna model sequence #0” code but it is returning the following error: > IndexError: list index out of range > > File “…path/RNALayout/rna_layout.py”, line 393, in place_residues > rprev = rlist[0] > > See reply log for Python traceback. > > Anything elementary that I am missing? My fasta file is very simple and it is stored in the Documents folder. > Regards,