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Physicochemical changes produced in DNA after alkylation

Lett, John T. ; Parkins, Gwenda M. ; Alexander, Peter

Archives of biochemistry and biophysics, 1962-04, Vol.97 (1), p.80-93 [Periódico revisado por pares]

United States: Elsevier Inc

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  • Título:
    Physicochemical changes produced in DNA after alkylation
  • Autor: Lett, John T. ; Parkins, Gwenda M. ; Alexander, Peter
  • Assuntos: Alkylation ; Antineoplastic Agents - chemistry ; DNA - chemistry ; Old Medline
  • É parte de: Archives of biochemistry and biophysics, 1962-04, Vol.97 (1), p.80-93
  • Notas: ObjectType-Article-1
    SourceType-Scholarly Journals-1
    ObjectType-Feature-2
    content type line 23
  • Descrição: Deoxyribonucleic acid (DNA) from salmon sperm was reacted in aqueous solution with different monofunctional alkylating agents, and changes in molecular weight, size, and ultraviolet absorption were observed at different times after the initial alkylation process was complete. Measurements made immediately after reaction show the DNA to have “coiled” (i.e., contracted in size to occupy a smaller volume in solution) without decreasing in molecular weight. The extent of alkylation necessary to produce “coiling” varied with the different agents used. One per cent alkylation of the nucleotides by propylene oxide causes no immediate coiling but produces a marked post-effect. On standing at 37 °C., the molecular weights of the alkylated DNA's decrease except in the case of DNA treated with ethyl methane sulfonate. DNA treated with ethyl methane sulfonate shows no post-treatment changes. Reaction with all the agents except ethyl methane sulfonate produced a change in the ultraviolet absorption spectrum, and a new peak appeared near 275 mμ. With a nitrogen mustard it was possible to show that the ultraviolet change did not occur immediately after alkylation but that it was a rapid post-treatment effect. The alkylated bases responsible for the changed absorption spectrum are labile and can be separated from the DNA by dialysis. No dialyzable material could be detected after alkylation with ethyl methane sulfonate. The post-treatment ultraviolet changes are believed in some cases to be due to a transalkylation reaction. The initial alkylation involves the phosphate group, to give a triester which then reacts with the purine bases. The alkylated purines, whether produced directly or by transalkylation are unstable, and are released from the DNA to give an “apurinic” residue which rapidly hydrolyzes at the sugar-phosphate bond. This sequence of events is responsible for the slow fall in molecular weight of alkylated DNA. The initial coiling reaction is attributed to esterification of phosphate groups.
  • Editor: United States: Elsevier Inc
  • Idioma: Inglês
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