I have been working with a very large structure of many subunits, the E.Coli Ribosome particle with the Signal Recognition Particle attached (PDB 2J28) I was able to create an image of the SRP part of the complex. I selected that subunit. And was able to hide all the other subunits. So with the subunit selected I tried to visualize only that image as a surface. Wouldn't let me, getting an error message that it was too large and I should somehow split it. Don't know how to do that. I know the whole dataset is very large, but the SRP portion is only 400 amino acids. A work around would be if I could somehow select the SRP subunit and have it as a dataset to reload as that subunit alone. Then not so big. Don't know how to do that either. Your suggestions. I couldn't find anything in the tutorials that might help. I was able to show the surface of another PDB file that was much smaller. Arthur G. Szabo Professor Emeritus Chemistry Wilfrid Laurier University Waterloo Ontario Canada.