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: Of the nonepisode biopsies , 7 and 4 biopsies showed minimal - type and mild - type chronic FK506 nephropathy , respectively .
### Output Text:
Of the nonepisode biopsies , 7 and 4 biopsies showed minimal - type and mild - type chronic <span class="chemical">FK506</span> nephropathy , respectively . 