2538
By performing fluorescence - activated cell sorting and Western blotting analyses , we established that enantiomer ( S ) - 2 - pentyl - 4 - pentynoic acid has higher apoptosis - inducing potential than VPA itself .
 ( S ) - 2 - pentyl - 4 - pentynoic acid, VPA
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 ( S ) - 2 - pentyl - 4 - pentynoic acid, VPA