19660
Bacteriopheophytin a in the active branch of the reaction center of rhodobacter sphaeroides is not disturbed by the protein matrix as shown by 13C photo - CIDNP MAS NMR .
 Chemical: Bacteriopheophytin a; Chemical: 13C
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: 13C