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: Atropine - MK801 did not offer any additional protection against DFP toxicity .
### Output Text:
<span class="chemical">Atropine</span> - <span class="chemical">MK801</span> did not offer any additional protection against <span class="chemical">DFP</span> toxicity . 