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Localization phenomena in a DNA double helix structure : A twisted ladder model

In this work we propose a model for DNA double helix within the tight-binding framework that incorporates the helicity of the molecules. We have studied localization properties of three DNAsequences,the periodic poly(dG)-poly(dC) and poly(dA)-poly(dT) sequences and the random ATGCsequence, all of which are coupled to backbone withrandom site energies representing the environmentalfluctuations. We observe that due to helicity of DNA, electron transport is greatly enhancedand there exists almost a disorder-strength independent critical value of the hopping integral, thataccounts for helicity of DNA, for which the electronic states become maximally extended. We havealso investigated the effect of backbone energetics on the transmission and I-V characteristics of DNA.