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: Ultrastructural damage and levels of 4 - hydroxy - 2 - nonenal ( 4HNE ) - protein adducts and 3 - nitrotyrosine ( 3NT ) were analyzed .
### Output Text:
Ultrastructural damage and levels of <span class="chemical">4 - hydroxy - 2 - nonenal</span> ( <span class="chemical">4HNE</span> ) - protein adducts and <span class="chemical">3 - nitrotyrosine</span> ( <span class="chemical">3NT</span> ) were analyzed . 