19337
The equilibrium metal - binding constants were determined by dilute solution potentiometric titration of monofunctional histidine - modified methoxy - PEG and were found to be consistent with binding constants of small molecule analogs previously studied .
 Chemical: histidine; Chemical: methoxy - PEG
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: histidine; Chemical: methoxy - PEG