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: Either alpha - T or alpha - TAc increases membrane packing and prevents TAM partition into model membranes .
### Output Text:
Either <span class="chemical">alpha - T</span> or <span class="chemical">alpha - TAc</span> increases membrane packing and prevents <span class="chemical">TAM</span> partition into model membranes . 