Seite - 5 - in Charge Transport in DNA - Insights from Simulations

CHAPTER1 Introduction The investigation of charge transfer processes constitutes an interface between physics, chemistry and biology. Chemical reactions are often accompanied by chargetransferprocessesnotonly inthe laboratory,butalso inbiologicalprocesses. Here,DNAoccupiesanoutstandingposition intheresearcherscommunity. Itsnat- ural feature to support charge transfer is seen in processes like radiative damage andrepairofDNAstrands in livingorganisms. In the lastyears, theevolvingfield ofmolecular electronicshasbroughtDNAinto the focusasapotential element for electronic circuits at the molecular scale. Special features like self-assembly and self-recognitionare aunique characteristic ofDNAoligomers. The conductivity of DNA has been studied intensively in the recent years.[1, 2] Yet, there are still features of charge transport (CT) that have not been resolved unambiguously yet. The research of CT in nucleic acids started with measure- mentsperformedon longDNAstrandsof several thousandbasepairs, in the form of ‘ropes’[3] or on supercoiledDNA.[4] In these early times, diametrically differ- ent conductivity of DNA under different conditions was reported, ranging from superconductivity[5] to insulation.[6] ThepioneeringstudyofCTin individualDNAoligomersappeared in2000,[7] and several further single-molecule experiments have been reported since then.[8–13] All of these studies are in aqualitative agreementupon the semi-conducting char- 5