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In addition , the use of this orthogonal experimental approach to measure the interactions between FtsZ oligomers ( GDP forms ) and polymers ( GTP forms ) with two variants ( a soluble form and a full - length protein incorporated in phospholipid bilayer nanodiscs ) of the ZipA protein , which provides membrane tethering to FtsZ , is described as well .
 GDP, GTP
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 GDP, GTP