As a robust platform for genome editing,CRISPR/Cas9 is currently being explored for engineering biology or therapeutics,yet means for quantitative detection of Cas9 proteins remain to be fully realized.Here,we expressed Cas9 proteins and developed a novel detection method that traced Cas9 based on radiolabeled iodine.Through optimizing the reaction conditions of reaction time,temperature and cycles,we obtained ^(125)I-Cas9 of high labeling yield.The prepared ^(125)I-Cas9 was stable in various media and preserved excellent genome editing efficiency.Thus,our strategy provides a convenient and efficient tool for further tracing biological behaviors of Cas9 proteins in living systems.
