19552
Purine - sensing ribozymes are designed by fusing the minimal version of the hammerhead ribozyme with bacterial guanine or adenine aptamers by modeling 3D interactions .
 Purine, guanine, adenine
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Purine, guanine, adenine