Abstract
In the present work we make a theoretical study of the steady state electric linear dichroism of DNA fragments in aqueous solution. The here developed theoretical approach considers a flexible bent rod model with a saturating induced dipole moment. The electric polarizability tensor of bent DNA fragments is calculated considering a phenomenological model which theoretical and experimental backgroung is presented here. The model has into account the electric polarizability longitudinal and transversal to the macroion. Molecular flexibility is described using an elastic potential. We consider DNA fragments originally bent with bending fluctuations around an average bending angle. The induced dipole moment is supposed constant once the electric field strength grows up at critical value. To calculate the reduced electric linear dichroism we determine the optical factor considering the basis of the bent DNA perpendicular to the molecular axis. The orientational distribution function has into account the anisotropic electric properties and the molecule flexibility. We applied the present theoretical background to fit electric dichroism experimental data of DNA fragments reported in the bibliography in a wide range of molecular weight and electric field. From these fits, values of DNA physical properties are estimated. We compare and discuss the results here obtained with the theoretical and experimental data presented by other authors. The original contributions of this work are: the inclusion of the transversal electric polarizability saturating with the electric field, the description of the electric properties with an electric polarizability tensor dependant on the bending angle and the use of an arc model originally bent.
Highlights
Electro-optical techniques are a useful tool to obtain structural parameters of molecules in solution
We applied the present theoretical background to fit electric dichroism experimental data of DNA fragments reported in the bibliography in a wide range of molecular weight and electric field
Many works apply electric birefringence (EB) and reduced electric linear dichroism (RELD) techniques to study the physicochemical properties of DNA fragments
Summary
Electro-optical techniques are a useful tool to obtain structural parameters of molecules in solution. Diekmann and others[1,2] measured RELD of DNA fragments and interpreted their experimental data based in a rigid rod like model with saturating induced electric dipole moment. These authors present RELD experimental curves of restriction fragments in a very wide rank of chain length and electric field strength. When interpreting limit values of RELD they concluded that the bent of DNA fragments affects the orientational distribution function From their arguments we can infer that a study of DNA electric dichroism in a wide range of molecular weight and electric field strength should include as relevant characteristics the molecular flexibility and the polyelectrolyte curvature.
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