A 2'-deoxynucleoside is constructed from a nucleobase and a 2'-deoxyribose. Ionizing radiation also injures nucleobases, some of which can be removed by piperidine. The lesions are cleaved, leaving a terminus with phosphate. Then, it is possible to estimate the yield of the lesions using the increase in the amount of termini with phosphate in piperidine-treated irradiated DNA.