Effect of the oligopeptide length on the DNA condensation process in aqueous-salt solutions

The methods of circular dichroism, ultraviolet spectrophotometry, dynamic light scattering, viscometry, dynamic birefringence, and atomic force microscopy are employed to study the conformational properties of the DNA molecule during its complexation with oligopeptides. Samples with c 2, 3, and 5 monomeric L-lysine residues are used. Experimental data evidence that in the diluted solutions (with a low ionic strength) of DNA with oligopeptides (with 3 and 5 monomeric units) the condensation of the macromolecule is observed at specific peptide concentrations. For the bipeptide the DNA condensation in the solution is not observed. In the DNA solutions with a high ionic strength (1 M NaCl), oligopeptides do not affect the macromolecule size.