text: Monothiophosphate is the anion [POS], which has C symmetry. A common salt is sodium monothiophosphate (NaPOS). Monothiophosphate is used in research as an analogue of phosphate in biochemistry. Monothiophosphate esters are biochemical reagents used in the study of transcription, substitution interference assays. Sometimes, "monothiophosphate" refers to esters such as (CHO)POS.