[{"from": "human", "value": "Design a molecule that meets the criteria outlined in the description. The molecule is a guanidinium ion that is the conjugate acid of methylguanidine; major species at pH 7.3. It is a conjugate acid of a methylguanidine."}, {"from": "gpt", "value": "[C][NH1+1][=C][Branch1][C][N][N]"}]