Chromatographic study of the UV photoproducts in uracil solid phase systems.

UV photoproducts were induced in two types of uracil solid phase systems: in evaporated and recrystallized thin layers and in dried aquaeous solution respectively. The nature of the photochemical reactions in the two systems was compared by gradient elution column chromatography. In the case of dried solution two types of cyclobutane dimers were isolated, but in recrystallized thin layers only one type was found. The efficiency of the reaction in evaporated layers was much higher than in those produced by drying. Based on the crystal structure of uracil and previous absorption spectroscopic studies of the photochemistry of thin crystalline layers it was stated, that the single type of photodimers produced in evaporated thin layers is characteristic for the photochemical reaction proceeding in crystal matrix; and its structure was proposed to be identical with that of the cis-syn stereoisomer dimer.