Meares C F, Bryant R G, Baldeschwieler J D, Shirley D A
Proc Natl Acad Sci U S A. 1969 Dec;64(4):1155-61. doi: 10.1073/pnas.64.4.1155.
The angular correlation of the 150-247 kev gamma-ray cascade of (111m)Cd is strongly perturbed when this nucleus is bound to the enzyme carbonic anhydrase. A comparison of the perturbed angular correlation for the apoenzyme with that for native carbonic anhydrase confirms that the (111m)Cd binds at the active region of the enzyme. These results provide good evidence that the perturbed angular correlation reflects the effective molecular rotational correlation time at the metal binding site, and that this radioactive nucleus can be used as a rotational tracer to label biological macromolecules. The qualitative dependence of the perturbed angular correlation of the (111m)Cd cascade on the molecular rotational correlation time at the metal binding site is illustrated using a cadmium-complex solution at various temperatures.
当（111m）镉的150 - 247千电子伏特γ射线级联与酶碳酸酐酶结合时，其角关联会受到强烈干扰。将脱辅基酶的受干扰角关联与天然碳酸酐酶的受干扰角关联进行比较，证实（111m）镉结合在酶的活性区域。这些结果充分证明，受干扰的角关联反映了金属结合位点处有效的分子旋转相关时间，并且这种放射性核可作为旋转示踪剂来标记生物大分子。通过使用不同温度下的镉络合物溶液，说明了（111m）镉级联的受干扰角关联对金属结合位点处分子旋转相关时间的定性依赖性。
