The effects of ultraviolet light on some components of the nucleic acids: III. Apurinic acid

Abstract

Abstract Apurinic acid, prepared from deoxyribonucleic acid, is destroyed by ultraviolet light much more rapidly than would be expected from the behaviour of the component pyrimidine‐nucleotides under this radiation. It is confirmed by analysis that both thymine and cytosine are sensitive. The destruction of thymine is supposed to be due to the occurrence of this pyrimidine in a more sensitive form, presumably comparable to the form present in a frozen solution. Upon adding an amount of adenine comparable to that of the purines removed, to apurinic acid, the decrease in extinction on irradiation resembles closely that of deoxyribonucleic acid. Consequently, it seems likely that the purines in deoxyribonucleic acid protect the pyrimidines to a certain extent against the U.V. radiation and that the sensitivity of deoxyribonucleic acid to U.V. radiation is caused by the pyrimidines present as constituent parts of the molecule. The primary action of this radiation on living cells may be caused by destruction of the pyrimidines in the nucleic acids.