19346
In contrast , when the adenine ligand interacts with partially folded messenger RNAs , the aptamer requires specifically bound Mg ( 2 + ) ions , as those observed in the crystal structure , to progress further towards the native form .
 Chemical: adenine; Chemical: Mg ( 2 + )
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: adenine, Mg ( 2 + ) 
Answer:
 Chemical: adenine; Chemical: Mg ( 2 + )