8419
The effects of combinations of the N1 substituent and C3 amide groups was extensively studied to compare enzyme inhibition , antiviral activity and protein binding effects on potency .
 Chemical: amide
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: amide