4PRZ:
reference: Selective inhibition of initiator versus executioner caspases using small peptides containing unnatural amino acids., Vickers CJ, Gonzalez-Paez GE, Litwin KM, Umotoy JC, Coutsias EA, Wolan DW, ACS Chem Biol. 2014 Oct 17;9(10):2194-8. doi: 10.1021/cb5004256. Epub 2014 Aug 5. PMID: 25079698

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