3BDC:
reference: Molecular determinants of the pK(a) values of Asp and Glu residues in staphylococcal nuclease., Castaneda CA, Fitch CA, Majumdar A, Khangulov V, Schlessman JL, Garcia-Moreno BE, Proteins. 2009 May 4;77(3):570-588. PMID: 19533744

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