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Using quantum chemical calculations and Protein Data Bank ( PDB ) searches on model systems , we investigate the energetics and geometric preferences for the stacking on amide groups of a large number of heteroarenes that are relevant to medicinal chemistry .
 Chemical: amide; Chemical: heteroarenes
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; Chemical: heteroarenes