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In HEK - 293 cultured cells , transfection efficiency significantly increased from 12 % to 30 % when pH decreased from 7 . 4 to 7 . 1 ( data normalized to Lipofectamine (TM) 2000 ) .
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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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