Single strand conformation of adenylate chains analysed by a specific photoreaction. Determination of structure by 5' residue.

The photoreactivity was analysed in various oligo- and polyadenylates: 1) The quantum yields of the specific photoreaction in poly(dA) and dApdA decrease with increasing temperature, whereas the quantum yield of the photodegradation in poly(rA) increases. 2) The photoreactivities of poly(2'MeA) and poly(2'EtA) closely correspond to that of poly(rA). 3) The photodegradation of rApdA is very similar to that of rAprA, whereas dAprA shows the same specific photoreaction as observed for dApdA. These data support the view, that the specific photoreaction observed in oligo(dA) and poly(dA) is dependent upon a specific conformation, which is not accessible to oligo(rA), poly(rA), poly(2'MeA) and poly(2'EtA). The specific conformation is determined by the nucleotide, which carries the internucleotide bond in the 3'-position.