In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: These results indicated that nocistatin , a new biologically active peptide , ameliorates impairments of spontaneous alternation and passive avoidance induced by scopolamine , and suggested that these peptides play opposite roles in learning and memory .
### Output Text:
These results indicated that <span class="chemical">nocistatin</span> , a new biologically active peptide , ameliorates impairments of spontaneous alternation and passive avoidance induced by <span class="chemical">scopolamine</span> , and suggested that these peptides play opposite roles in learning and memory . 