4941
They suggest that , contrary to the commonly accepted mechanism , the attacking O ( 2 ) is not incorporated as an active site ligand but , rather , acts as an electron acceptor .
 Chemical: O ( 2 )
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: O ( 2 )