diff --git a/modelbuilder.py b/modelbuilder.py
index f0381a5..109ff9f 100644
--- a/modelbuilder.py
+++ b/modelbuilder.py
@@ -137,7 +137,7 @@ class LoopModelBuilder:
             workdir.mkdir(exist_ok=True, parents=True)
             mc_fasta = self.analyzer_instance.find_most_similar(self.sequences[mc]) # get misschain fasta file
             # write fasta file
-            mc_fasta_record = SeqRecord(mc_fasta, id=f'{mc}', description=f'{self.pdb_id}|{mc}')
+            mc_fasta_record = SeqRecord(mc_fasta, id=f'{mc}', description=f'{self.pdb_id}_{mc}')
             out_fasta_file = workdir.joinpath(f'{self.analyzer_instance.pid}_{mc}.fasta')
             self.analyzer_instance.write_seq_to_fasta_single_line(mc_fasta_record, out_fasta_file)
             self.logger.info(f'>{self.pdb_id}|{mc}|missing site:{self.missing_info[mc]}|length:{len(mc_fasta)}')