27761
Ligands for receptors more distantly related to the X - ray template , i . e . P2YRs , have been introduced and are mainly used as pharmacological tools for elucidating the physiological role of extracellular nucleotides .
 Chemical: nucleotides
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: nucleotides 
Answer:
 Chemical: nucleotides