7519
While silk - like polymers without elastin - like blocks form fibrils by heterogeneous nucleation , leading to monodisperse populations , the elastin - like blocks allow for homogeneous nucleation , which gives rise to polydisperse length distributions , as well as a concentration - dependent fibril length .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities:  
Answer:
 None