9063
The electronic structure of the Fe - O ( 2 ) center in oxy - hemoglobin and oxy - myoglobin is a long - standing issue in the field of bioinorganic chemistry .
 Chemical: Fe; 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: Fe; Chemical: O ( 2 )