28906
The design was based on a docking study hypothesizing that substituents in the 2 ' - position would protrude into a region where differences among the NMDA receptors GluN2 subunits exist .
 NMDA
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 NMDA