On Sun, May 23, 2010 at 6:33 PM, Maia Cherney <chern@ualberta.ca> wrote:
Thank you for your help. However, I have 4  Mg ions  in the au, so all Mg ions (and all coordinated ligands) got connected. I need only coordination for one Mg.

Then you need to qualify the selection with the residue number, and repeat up to 4 times.  Same principle still applies, though:

dist (elem mg and resid 341), (all within 2.2 of (elem mg and resid 341))

this particular example may be unnecessarily verbose if the residue number is unique.