1,4-Anhydro-5-O-[bis(4-methoxyphenyl)phenylmethyl]-2-deoxy-D-erythro-pentitol is used as a reactant in the solution conformation of an abasic DNA undecamer duplex with unpaired thymine. Also used in direct fluorescence monitoring of uracil DNA glycosylase activity in vitro and in bacterial cells using short single-stranded DNA oligomers containing pyrene α-deoxyriboside adjacent to uracil.