No abstract

Long-distance transfer of a positive charge through DNA can be described by a hopping model. In double strands where the (A:T) n bridges between the guanines are short (n ≥ 3), the charge hops only between guanines, and each hopping step depends strongly upon the guanine to guanine distances. In strands where the (A:T) n sequences between the guanines are rather long (n ≥ 4), also the adenines act as charge carriers. To predict the yields of the H 2 O-trapping products one has to take into account not only the charge-transfer rates but also the rates of H 2 O-trapping reactions.In the 1990s, the question of long-distance electron transfer through DNA raised a controversial discussion [1]. We entered this area three years ago by studying radical-induced DNA strand cleavage reactions. Our experiments showed that photolysis of a 4'-acylated nucleoside in the DNA double strand 1 yields radical cation 2 that selectively oxidizes guanine (G) and forms a guanine radical cation (G •+ ) in 3 (Fig.

Als Relaisstationen, über die sich die positive Ladung verteilt, fungieren Guaninbasen beim weit reichenden Ladungstransport durch DNA. Fehler in den Guanin:Cytosin(G:C)‐Basenpaaren verringern drastisch die Effizienz dieses Ladungstransportes. Das Bild zeigt das Histogramm der Strangbruchprodukte PG und PGGG eines 54‐mers, von dem oben nur die entscheidende Sequenz angegeben ist.

Electron transport through DNA occurs over very long distances (100 Å and more). The process follows a hopping mechanism and depends upon the DNA sequence. The efficiency of the charge transport is only slightly distance dependent because in most cases the H2O trapping of the charge is slower than the electron transfer. These findings show the potential of substituted DNAs as new materials for nanoelectronics in the future.