[{"from": "human", "value": "Based on the given information, design a molecule that meets the desired specifications. The molecule is a radioisotope of strontium, a heavy metal found naturally as a non-radioactive element.  With a half-life of 50 days, strontium-89 is a beta emitter that is metabolized much like calcium.  This agent is preferentially absorbed by osteoblastic bone metastases. (NCI04)"}, {"from": "gpt", "value": "[89Sr]"}]