Thymidine-13C10 (DThyd-13C10, NSC 21548-13C10) is 13C-labeled Thymidine (HY-N1150). Thymidine, a specific precursor of deoxyribonucleic acid, is used as a cell synchronizing agent. Thymidine is a DNA synthesis inhibitor that can arrest cell at G1/S bound