This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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n. A chemical compound or group that is attracted to nuclei and tends to donate or share electrons.

n. a compound or functional group that is attractive to centres of positive charge, and donates electrons, especially donating an electron pair to an electrophile to form a bond

"The pseuoduridine synthases (Y synthases) are responsible for this reaction, and they fall into five families that share very limited sequence similarity but have the same overall fold and active site architecture, including an essential Asp that likely serves as both a nucleophile and a general base during the reaction."

Lewis base   

nucleophilic   

electrophile    surfactant    bromonium    carbanion    dienophile