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Sequence-based assignment of the heme ligands is inference from similarity, not structure.\nexposure: Ser530 replaced with alanine and with asparagine, and tetranitromethane modification with ibuprofen protection\nevidence_span: {\"source_cache\": \"artifacts/aspirin-research/2144687.abstract.txt\", \"locator\": \"Indexed abstract; zero-based, end-exclusive Unicode character offsets\", \"file_sha256\": \"0a66f17b41129423ecb73bf520dad47b666792a6477552db04272474fc79be24\", \"start_char\": 0, \"end_char\": 1595, \"text_sha256\": \"0a66f17b41129423ecb73bf520dad47b666792a6477552db04272474fc79be24\"}\n[asa-p2144687] Structure-function relationships in sheep, mouse, and human prostaglandin endoperoxide G/H synthases. 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