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: Inhibition studies , kinetic analysis and molecular dynamics were undertaken to understand how this mutation disrupts the catalytic triad and determines a " silent " phenotype .
### Output Text:
Inhibition studies , kinetic analysis and molecular dynamics were undertaken to understand how this mutation disrupts the catalytic triad and determines a " silent " phenotype . 