2G2S:
reference: Understanding GFP Posttranslational Chemistry: Structures of Designed Variants that Achieve Backbone Fragmentation, Hydrolysis, and Decarboxylation., Barondeau DP, Kassmann CJ, Tainer JA, Getzoff ED, J Am Chem Soc. 2006 Apr 12;128(14):4685-93. PMID: 16594705

This OCA Structure page
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