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: Animals of the S - I group exhibited significantly ( Pp less than 0 . 05 ) greater mortality from the effects of isoproterenol than animals of the E - I group .
### Output Text:
Animals of the S - I group exhibited significantly ( Pp less than 0 . 05 ) greater mortality from the effects of <span class="chemical">isoproterenol</span> than animals of the E - I group . 