[gmx-users] problem in converting pbd file to gro file

[sunzhmd at mail.ustc.edu.cn]

 Dear gmx-users,

 I download a pdb file of DEOXYRIBONUCLEIC ACID from a pdb server:
 ftp,rcsb.org/pub/pdb

 Then I want to convert it into a gromacs structure file .gro by the
 command

 pdb2gmx -f filename.pdb

 Then a error was encountered which reads

 Residue 'A' not found in residue topology file database

 I do not know why. I wonder if anyone can do me a favor and help me with
 this question.

 Thank you and best regards to all.