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 both types , purinoceptor desensitization with alpha , beta - methylene adenosine - 5 ' - triphosphate ( alpha , beta - meATP ) caused further reductions at low frequencies ( < 10 Hz ) .
### Output Text:
In both types , purinoceptor desensitization with <span class="chemical">alpha , beta - methylene adenosine - 5 ' - triphosphate</span> ( <span class="chemical">alpha , beta - meATP</span> ) caused further reductions at low frequencies ( < 10 Hz ) . 