13071
Furthermore , our results indicate that although the stalk and transmembrane regions may be mainly responsible for the tetramer formation of MV - H , the head domain alone can form tetramers , albeit at a low efficiency .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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