biocide products. The three major N-halogenated derivatives are dichlorodimethylhydantoin (DCDMH), bromochlorodimethylhydantoin (BCDMH), and dibromodimethylhydantoin (DBDMH). A mixed ethyl-methyl analogue, 1,3-dichloro-5-ethyl-5-methylimidazolidine-2,4-dione (bromochloroethylmethylhydantoin), is also used in mixtures with the above. DNA oxidation to hydantoins after cell death A high proportion of cytosine and thymine bases in DNA are oxidized to hydantoins over time after the death of an organism. Such modifications block DNA polymerases and thus prevents PCR from working. Such damage is a problem when dealing with ancient DNA samples. External links and further reading Hazard DB: Hydantoin English Translation of 1926 German review article on the Preparation of hydantoins by Heinrich Biltz and Karl Slotta References