Experimental Factor Ontology identifier EFO_0021400 (4-acetamidobutanoate-to-X-03056--N-[3-(2-Oxopyrrolidin-1-yl)propyl]acetamide ratio) is quantification of the ratio of 4-acetamidobutanoate to X-03056--N-[3-(2-Oxopyrrolidin-1-yl)propyl]acetamide in a sample.