[Photoaffinity modification of amino acid derivatives of oligonucleotides in a complementary complex]

Intracomplex photochemical interaction of photoactive derivatives R-CONH(CH2)3NH-pGATACCAA, where R= p-azidotetrafluorophenyl (I) or 2-nitro-5-azidophenyl (II), and 5'-phospho-p-azidoanilide pGATACCAA (III) with a target - oligonucleotide *pGGTATCp (IV) and its derivatives *pGGTATCp-NH(CH2)3NHX, where X = H (V), Phe (VI), or Lys (VII), was studied. According to electrophoretic data, photoreagent (I) gives rise to a covalent photoadduct with compound (IV) as well as with derivatives (VI) and (VII). In the case of reagent (II), only targets (V) - (VII) including aliphatic amino groups participate in the photocoupling. Upon irradiation of the duplexes comprising photoreagent (III) and targets (V)-(VII), the process is accompanied by the cleavage of the reagent's oligonucleotide moiety off the photomodification product. A plausible mechanism of the cleavage is discussed.