[{"from": "human", "value": "Design a molecule that meets the criteria outlined in the description. The molecule is a methyl-branched fatty acid anion that is the conjugate base of isotridecanoic acid, obtained by deprotonation of the carboxy group; major species at pH 7.3. It is a conjugate base of an isotridecanoic acid."}, {"from": "gpt", "value": "[C][C][Branch1][C][C][C][C][C][C][C][C][C][C][C][C][=Branch1][C][=O][O-1]"}]