104 research outputs found
Oxidation of single-stranded oligonucleotides by carbonate radical anions: generating intrastrand cross-links between guanine and thymine bases separated by cytosines
The carbonate radical anion is a biologically important one-electron oxidant that can directly abstract an electron from guanine, the most easily oxidizable DNA base. Oxidation of the 5′-d(CCTACGCTACC) sequence by photochemically generated CO3·− radicals in low steady-state concentrations relevant to biological processes results in the formation of spiroiminodihydantoin diastereomers and a previously unknown lesion. The latter was excised from the oxidized oligonucleotides by enzymatic digestion with nuclease P1 and alkaline phosphatase and identified by LC-MS/MS as an unusual intrastrand cross-link between guanine and thymine. In order to further characterize the structure of this lesion, 5′-d(GpCpT) was exposed to CO3·− radicals, and the cyclic nature of the 5′-d(G*pCpT*) cross-link in which the guanine C8-atom is bound to the thymine N3-atom was confirmed by LC-MS/MS, 1D and 2D NMR studies. The effect of bridging C bases on the cross-link formation was studied in the series of 5′-d(GpCnpT) and 5′-d(TpCnpG) sequences with n = 0, 1, 2 and 3. Formation of the G*-T* cross-links is most efficient in the case of 5′-d(GpCpT). Cross-link formation (n = 0) was also observed in double-stranded DNA molecules derived from the self-complementary 5′-d(TTACGTACGTAA) sequence following exposure to CO3·− radicals and enzymatic excision of the 5′-d(G*pT*) product
Description d'un caisson métallique : pour la construction des jetées, ports, bassins, quais, docks ... destiné principalement aux propiétaires de domaines sur les bords de la mer our des rivières, et aux propiétaires de mines de fer et autres
Título original: A description of the patent metallic caisso
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