RI-1 is a potent and selective inhibitor of RAD51 (IC50 = 5-30 μM). It specifically reduces gene conversion in human cells and stimulates single strand annealing. It covalently binds to Cys319 on the surface of RAD51 and disrupts protein-protein interaction. It potentiates the effect of DNA-damaging agents on tumor cells and is a novel tool for studying DNA repair in cells. Potentiates the killing of glioblastoma cells by ionizing radiation and alkylating drugs. MW: 361.61. Purity ≥98% by TLC