title: Studies of the effects of ultraviolet radiation on the structural integrities of ribosomal RNA components of the Escherichia coli 50S ribosomal subunit.
abstract: The effects of 254-nm radiation on the structural integrities of free and 50S ribosome-bound 5S and 23S ribosomal ribonucleic acids (rRNA) have been elucidated. Irradiation of aqueous solutions of Escherichia coli 50S ribosomes with 253.7-nm radiation results in the formation of single-strand breaks in double-stranded regions of the 23S rRNA component, but not in rRNA chain scission, and destabilization of the secondary structure of the 23S rRNA toward denaturation. The minimum doses of 253.7-nm radiation required for the first detection of the two effects are 7 x 10(19) quanta for the production of single-strand breaks in double-stranded regions of the 23S rRNA, and less than 2.3 x 10(19) quanta for destabilization of the 23S rRNA secondary structure. Free 23S rRNA is resistant toward photoinduced chain breakage at doses of 253.7-nm radiation up to at least 2.3 x 10(20) and is much less sensitive toward destabilization of secondary structure than ribosome-bound 23S rRNA toward chain breakage, 50S ribosome-bound 5S rRNA is resistant toward chain breakage at doses of 253.7-nm radiation up to at least 2.3 x 10(20) quanta. Ribosome-bound 5S and 23S rRNA are also not photosensitive toward intermolecular 5S/23S rRNA crosslinkage.
mesh_terms: D004926:Escherichia coli / Q000528:radiation effects* / Q000648:ultrastructure; D008970:Molecular Weight; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D012335:RNA, Ribosomal / Q000528:radiation effects*; D012270:Ribosomes / Q000528:radiation effects* / Q000648:ultrastructure; D014466:Ultraviolet Rays
chemical_list: D012335:RNA, Ribosomal