> I have a peptide that contains HYP and CGU residues. And I cannot
> use leap to save them. Do any one know is there any force field in
> amber that can do this? Now, I used ff03 and gaff, but i failed do
> that.
You could use the R.E.D. tools to generate required fragments
(central, N-terminal and/or C-terminal) for your unusual amino-acid(s).
