17050
Here we report a single - molecule F o rster resonance energy transfer ( smFRET ) system that directly monitors the movement of a DNA substrate between the pol and exo sites of DNA polymerase I Klenow fragment ( KF ) .
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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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