11899
This state , displaying an elongated C ( 4 ) = O bond , triggers ( 6 - 4 ) dimer formation by reaction with the C ( 5 ) = C ( 6 ) double bond of the adjacent thymine , followed by a second intersystem crossing , which acts as a gate between the excited state of the reactant and the ground state of the photoproduct .
 Chemical: thymine
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: thymine