[COOT] DNA mutation

[Taufik Al-Sarraj]

Hello everyone,

I am new to Coot, I am trying to do a DNA mutation but unfortunately i 
have not been successful. I am using Mutate Residue Range.
The error message i get is
'INFO:: mutate 2  to a ALA
DISASTER! Not all necessary atoms found in residue  2
 CA is missing
 C is missing
 N is missing
failure to get orientation matrix'

I tried the do mutation with a pdb structure from pdb.org 
<http://pdb.org> 1DGC, and i tried to do a mutation on a dna created 
using nucgen in amber. Both attempts gave me the error above.

any help would be greatly appreciated.
Taufik