[PyMOL] How to draw a cartoon representation on secondary structures containing beta-amino acids?

Dear all, I have a small helical pseudopeptide with mixed alpha and beta amino-acids. How can I make a cartoon representation of this helix with Pymol? For the moment, I have selected the peptide backbone atoms and tried the alter command to force pymol to recognize the helix but it do not

Re: [PyMOL] How to draw a cartoon representation on secondary structures containing beta-amino acids?

Thanks Joseph and Thomas for your replies. When I use the as cartoon commands, all my molecule disappear. My *pdb file could be the problem as it is a *cif crystal structure file (converted with mercury) from the cambridge crystal data. Cheers, Baptiste 2011/8/16 Thomas Holder