When I run the program, I get no errors, but no atoms are selected:
CHARMM> ! unsaturation check; beta chain
CHARMM> set ub = 0
Parameter: UB <- "0"
CHARMM> define unsat sele atom A 1 C2@C .and. chem CEL1 end
Parameter: C -> "2"
SELRPN> 0 atoms have been selected out of 36716
What am I doing wrong?