OLIGONUCLEOTIDE PHOTOPRODUCTS FORMED BY PHOTOLYSIS OF POLYRIBOBROMOURIDYLIC ACID

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Abstract
Abstract— Polyribobromouridylic acid was irradiated with 313 nm light at an exposure of ˜ 190 pE/cm*. Oligonucleotides found after RNase hydrolysis of the photolysed poly‐rBrU were isolated by DEAE‐cellulose chromatography and partially characterized. The dmucleo‐tide fraction, found in highest amounts, was not susceptible to hydrolysis by KOH or snake venom phosphodiesterase and may contain a coupled photoproduct. The properties of the dinucleotide were not those of a molecule containing a cyclobutane‐type dimer, but were compatible with the properties of a coupled product similar to 5–5′‐diuracil. The trinucleotide fraction probably consisted of more than one component. One component may contain a dimeric photoproduct. The tetranucleotide material was sensitive to cleavage into fragments by KOH, and could consist of adjacent photoproducts of the types found in the di‐ and trinucleotide fractions. The photoproducts formed over a range of lower doses of light were found to have properties similar to those found at high doses.