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Using a combination of hydrogen / deuterium exchange coupled to NMR spectroscopy , hydroxyl radical probing detected by mass spectrometry , and site - directed mutagenesis , we demonstrate that stop mutants of the human prion protein have a conserved amyloid core .
 Chemical: hydrogen; Chemical: deuterium; Chemical: hydroxyl
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: hydrogen; Chemical: deuterium; Chemical: hydroxyl