7873
In this study , we investigated the effect of modification with polyethylene glycol ( PEG ) on the in vivo stability of Hu BChE .
 polyethylene glycol, PEG
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 polyethylene glycol, PEG