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Our studies suggest that coelenterazine bound within the anaerobic complex might be a mixture of N7 - protonated and C2 ( - ) anionic forms , and that oxygen shifts the equilibrium in favor of the C2 ( - ) anion as a result of peroxy anion formation .
 coelenterazine, N7, C2 ( - ), oxygen, C2 ( - ), peroxy
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 coelenterazine, N7, C2 ( - ), oxygen, C2 ( - ), peroxy