21691
The structures of three aromatic - rich isolated peptides , Ac - Phe - Phe - NH2 ( FF ) , Ac - Trp - Tyr - NH2 ( WY ) , and Ac - Phe - Phe - Phe - NH2 ( FFF ) , all in the gas phase , have been studied by infrared - ultraviolet ( IR / UV ) double resonance laser spectroscopy , aided by dispersion - corrected density functional theory ( DFT - D ) calculations .
 Chemical: Ac - Phe - Phe - NH2; Chemical: Ac - Trp - Tyr - NH2; Chemical: Ac - Phe - Phe - Phe - NH2
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: Ac - Phe - Phe - NH2; Chemical: Ac - Trp - Tyr - NH2; Chemical: Ac - Phe - Phe - Phe - NH2