7078
In this study , we used the substituted - cysteine accessibility method ( SCAM ) to identify specific residues of the fourth transmembrane domain ( TM4 ) that contribute to the formation of the binding pocket of CXCR4 in its inactive and active state .
 Chemical: cysteine
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: cysteine