20113
In contrast , the remarkably linear pH dependence of the second step is related to the uniform reduction in global protein charge with increasing pH below pI , accompanied by an attractive force due to surface charge fluctuations .
 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