these data indicate that the nonprotein chromophore of neocarzinostatin , in the presence of a reducing substance ( 2-mercaptoethanol ) and molecular oxygen , selectively oxidizes the 5 ' carbon of nucleosides in dna to the aldehyde , resulting in a strand break and a dna fragment bearing nucleoside-5'-aldehyde at its 5 ' end .
C0012854
dna
C0000702
a dna