2UWU:
reference: pH Modulates the Quinone Position in the Photosynthetic Reaction Center from Rhodobacter sphaeroides in the Neutral and Charge Separated States., Koepke J, Krammer EM, Klingen AR, Sebban P, Ullmann GM, Fritzsch G, J Mol Biol. 2007 Aug 10;371(2):396-409. Epub 2007 May 10. PMID: 17570397

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