Given the task definition and input, reply with output. In this task, you are given a sentence. You are expected to recognize the name of gene or protein. Although there might be several correct answers, you need to write one of them.

 The receptor concentration of the low affinity site ( 0 . 30 pmol / mg protein ) was approximately twice that of the high affinity site ( 0 . 14 pmol / mg protein ) .

high affinity site