it sends back a fatal error if you don't put in a tp file. I'm more than happy to send in a tpr file, I just need to figure out how to generate it. -- View this message in context: http://gromacs.5086.x6.nabble.com/g-sas-on-pdb-files-tp5009248p5009250.html Sent from the GROMACS Users Forum mailing list archive at Nabble.com.