13070
These observations suggest that the dimer - dimer interactions of the MV - H head domain , especially that in form I , contribute to triggering membrane fusion , and that conformational shift of head domain tetramers plays a role in the process .
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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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