Disorder and fluctuations in nonlinear excitations in DNA

We study the e ects of the sequence on the propagation of nonlinear excitations in simple models of DNA, and how those e ects are modi ed by noise. Starting from previous results on soliton dynamics on lattices de ned by aperiodic potentials [23], we analyze the behavior of lattices built from real DNA sequences obtained from human genome data. We con rm the existence of threshold forces, already found in Fibonacci sequences, and of stop positions highly dependent on the speci c sequence. Another relevant conclusion is that the e ective potential, a collective coordinate formalism introduced by Salerno and Kivshar [21] is a useful tool to identify key regions that control the behaviour of a larger sequence. We then study how the uctuations can assist the propagation process by helping the excitations to escape the stop positions. Our conclusions point out to improvements of the model which look promising to describe mechanical denaturation of DNA. Finally, we also consider how randomly distributed energy focus on the chain as a function of the sequenceThis work has been supported by the Ministerio de Ciencia y Tecnología of Spain through grant BFM2003-07749- C05-01. S.C. is supported by a fellowship from the Consejería de Educación de la Comunidad Autónoma de Madrid and the Fondo Social Europeo.Publicad