Photoreaction of thymidine with primary amines. Application to specific modification of DNA.

Irradiation of calf thymus DNA with 254-nm light in the presence of n-butylamine resulted in the formation of l-n-butylthymine. The progress of the reaction can be easily monitored by the appearance of a new absorption band at 300 nm by UV spectroscopy. Model experiments on TpdA indicated that strand scission may occur preferentially at thymines during the photoreaction between DNA and n-butylamine. Because of its high selectively to Thyd, this type of photoreaction with n-butylamine may be used as a new method for selective release of thymine moieties from DNA.