Abstract Photohydrates are formed in high yield when uridine (Urd), 2′-deoxyuridine (dUrd), cytidine (Cyd) and 2′-deoxycytidine (dCyd) are irradiated with UVC in aqueous solution. The thermal reactions of the photohydrates of Urd with amines at pH values near pH 7.5 have been studied using UV spectroscopy, HPLC, mass spectrometry and, in some cases, NMR. It has been found that a number of amines (ie. ethylenediamine, N, N′- ...