3007
By simulated annealing analysis and molecular dynamics modeling , two hydrophobic amino acids , F - 18 and W - 21 , in the hinge region were predicted to be relatively surface - exposed and to interact with the aqueous solvent .
 amino acids
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 amino acids