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DAMAGE TO URACIL‐ AND ADENINE‐CONTAINING BASES, NUCLEOSIDES, NUCLEOTIDES AND POLYNUCLEOTIDES: QUANTUM YIELDS ON IRRADIATION AT 193 AND 254 NM
Author(s) -
Gurzadyan Gagik G.,
Görner Helmut
Publication year - 1994
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1994.tb05111.x
Subject(s) - polynucleotide , quantum yield , chemistry , chromophore , uracil , photochemistry , singlet state , irradiation , moiety , aqueous solution , nucleotide , stereochemistry , excited state , dna , fluorescence , physics , biochemistry , quantum mechanics , nuclear physics , gene
Photoreactions, such as base release and decomposition of the base moiety, induced by either 20 ns laser pulses at 193 nm or continuous 254 nm irradiation, were studied for a series of uracil and adenine derivatives in neutral aqueous solution. The quantum yield of chromophore loss (φ) depends significantly on the nature of the nucleic acid constituent and the saturating gas (Ar, N 2 O or O 2 ). In the case of polynucleotides the destruction of nucleotides was measured by high‐performance liquid chromatography after hydrolysis; the quantum yields (φ) are comparable to those of chromophore loss or larger. The φ cl and aφ dn of 0.04–0.1 for poly(U) and poly(dU), obtained for both wavelengths of irradiation, are due to processes originating from the lowest excited singlet state, i.e . formation of photohydrates and photodimers, and a second part from photoionization using λ irr = 193 nm. Irradiation at 193 nm effectively splits pyrimidine dimers and thus reverts them into monomers. The quantum yield for release of undamaged bases (φ br ) from nucleosides, nucleotides and polynucleotides upon irradiation at 254 nm is typically φ br = (0.1–1) × 10 −4 Breakage of the N ‐glycosidic bond is significantly more efficient for λ irr =193 nm, e.g. φ br = 1.1 × 10 −3 , 0.8 × 10 −3 , 4.3 × 10 −3 and 0.5 × 10 −3 for poly(A), poly(dA), poly(U) and poly(dU) in Ar‐saturated solution, respectively. Enhanced φ values for λ irr = 193 nm, essentially for adenine and its derivatives, are caused by photo‐processes that are initiated by photoionization.