I have a pdb file for the 16 monomers of the coarse-grained GPCRs and its corresponded trajectory in dcd which were prepared by the replication of the same system. As the result In both files all the monomers are defined as the same letter of the chain (X). My question: are there an easy way to assign a unique letter to each of the monomers in the both files to facilitate the further analysis ? Alternatively can I assign the unique name of the chains for each of the monomers during the replication of the initial system via genconf?