Elaine: Relating to your instructions of last 19 Nov (I printed your mail, then unfortunately I deleted it) how to align a protein into a membrane (for both I have valid pdb and valid Amber parameters) I am probably made elusive mistakes at the stage of saving new pdbs. I aligned the protein into the membrane, then (with protein selected and membrane not active) I saved the new pdb, getting two files, "0" for the membrane and "1" for the protein. In Amber LEaP both these pdb file could be loaded and combined, however save top/crd failed because something was wrong with the membrane file. In fact, if the original pdb for the membrane is used, top/crd can be saved, though the protein is not accurately aligned. Clearly, my plan is to remove superimpositions among molecules for the "whole" obtained from Amber. Thanks francesco pietra ____________________________________________________________________________________ Be a better pen pal. Text or chat with friends inside Yahoo! Mail. See how. http://overview.mail.yahoo.com/