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: In these HPMA copolymers , DOX was covalently bound via peptide linkages that were either non - biodegradable ( Gly - Gly ) or degradable by lysosomal proteinases ( Gly - Phe - Leu - Gly ) .
### Output Text:
In these <span class="chemical">HPMA</span> copolymers , <span class="chemical">DOX</span> was covalently bound via peptide linkages that were either non - biodegradable ( Gly - Gly ) or degradable by lysosomal proteinases ( <span class="chemical">Gly - Phe - Leu - Gly</span> ) . 