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: It is concluded that both selective urinary enzymes and the molecular weight pattern of urinary proteins can be used to provide diagnostic information about the possible site of renal damage .
### Output Text:
It is concluded that both selective urinary enzymes and the molecular weight pattern of urinary proteins can be used to provide diagnostic information about the possible site of renal damage . 