2SAR:
reference: Determination and restrained least-squares refinement of the structures of ribonuclease Sa and its complex with 3'-guanylic acid at 1.8 A resolution., Sevcik J, Dodson EJ, Dodson GG, Acta Crystallogr B 1991 Apr 1;47 ( Pt 2):240-53. PMID: 1654932

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