19067
Co - immunoprecipitation and pull - down studies showed that only Ca ( 2 + ) - bound calmodulin was able to bind DdCAD - 1 .
 Ca ( 2 + )
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Ca ( 2 + )