you seem to have changed the type of the N atom of PCA
from NX1 (or whatever it was originally) to NH3, so
now the two bond length types within PCA and
involving the nitrogen are undefined; you
can fix this in the parameter file you got
from hic-up
the third one is the bond that links your N-terminal
PCA to the second residues; you'll have to add that
to your parameter file
--gerard
