Structural deformations of the DNA double helix in the first stages of DNA transcription studied with a simple model

Abstract

Abstract A very simple model of DNA in biological media, consisting of electric charges related to the phosphate groups and to counterions immersed in structured media of constant permittivity, is introduced and tested with the study of a model for the first stages of the DNA transcription. This process is modeled into two steps involving three ‘states’: (1) the DNA system at the equilibrium, (2) the DNA with a small portion deprived of counterions, and (3) the DNA with a partial opening of the double helix in correspondence of the zone deprived of counterions. An extensive investigation involving as variable parameters the length of the DNA specimen (from 31 to 1511 base pairs), the amount of condensed counterion charge (from complete compensation to zero), and the geometrical parameters identifying the local opening has shown that the proposed transcription mechanism is reasonable, and that the DNA model considered here may fill a gap between accurate models including all the interactions—and employed at present for small fragments—and unstructured models addressed to inspect the behavior at the limit of infinite DNA length.

Keywords

Affiliated Institutions

• University of Pisa IT

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