19661
The electronic structure of bacteriopheophytin a ( BPhe a ) , the primary electron acceptor ( Phi A ) in photosynthetic reaction centers ( RCs ) of the purple bacterium Rhodobacter sphaeroides , is investigated by photochemically induced dynamic nuclear polarization ( photo - CIDNP ) magic - angle spinning ( MAS ) NMR spectroscopy at atomic resolution .
 Chemical: bacteriopheophytin a; Chemical: BPhe a
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: bacteriopheophytin a; Chemical: BPhe a