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By using various isotope labeling systems , introduced by adding different ( 13 ) C selectively labeled delta - aminolevulinic acid precursors in the growing medium of R . sphaeroides wild type ( WT ) , we were able to extract light - induced ( 13 ) C NMR signals originating from the primary electron acceptor .
 Chemical: ( 13 ) C; Chemical: delta - aminolevulinic acid; Chemical: ( 13 ) C
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: ( 13 ) C; Chemical: delta - aminolevulinic acid; Chemical: ( 13 ) C