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

Abstract

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 с 2, 3, and 5 monomeric Llysine 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.

Biophysical and Structural Characterisation of Nucleic Acid Complexes with Modified Cyclodextrins Using Circular Dichroism

“…48 In contrast, circular dichroism studies have also shown that when the interaction between pDNA and a vector is relatively weak, the changes in pDNA conformation are negligible, for example, in the case of a PEGylated polymer. 17,20 Although we do not see dramatic conformational changes for complexed pDNA within the MR range studied here, generally the circular dichroism profiles are distinct to that of uncomplexed pDNA, with red-shifting clearly observed for MRs 5 and 20 and less noticeably for MR 10. It has been suggested that the maximal changes in pDNA conformation occur close to the point of vector:pDNA charge neutrality, 41,46 whereas in the current study the cationic CD1 was present in excess at all MRs.…”

“…Circular dichroism is a highly sensitive technique which can detect changes in the secondary structure of DNA and RNA molecules and has been used to monitor interaction of nucleic acids with non-viral gene delivery vectors. [16][17][18][19][20] It is an important analytical method which can be used to shed further light on the conformational requirements for transfection and on the relationship between nucleic acid conformation and the ability to achieve gene expression or silencing. Circular dichroism has been used to investigate the changes in DNA secondary and tertiary conformation which occur after condensation by cationic vectors.…”

Electrostatic Interactions in the Formation of DNA Complexes with Cis- and Trans-Isomers of Azobenzene-Containing Surfactants in Solutions with Di- and Trivalent Metal Ions

“…Figure a also demonstrates that the DNA concentration has no influence on the measured parameters; only the concentration of the introduced cobalt ions is important and not the charge ratio, as is observed for the DNA–surfactant interaction. This difference in the DNA binding with small ions and with polycations was analyzed earlier in this Article . Interestingly, surfactant influence on DNA polyelectrolyte swelling in this regard is similar to that for polycations, apparently due to the fact that in solutions the surfactant molecules in most cases form associates with each other.…”

“…It should be noted that DNA packaging caused by cationic surfactants in aqueous solutions occurs at the charge ratio of about Z = 1, as it is usually observed in DNA solutions with polycations. The formation of nanosized structures in DNA–surfactant solutions is similar to that in DNA solutions with polycations, as it follows from the phase diagrams. ,, …”

“…The formation of nanosized structures in DNA−surfactant solutions is similar to that in DNA solutions with polycations, as it follows from the phase diagrams. 13,30,34 Cationic surfactants are amphiphilic molecules. Their binding to DNA decreases the charge density of the macromolecule and also transforms the environment around the double helix via the formation of a hydrophobic "coat" of the surfactant tails, which leads to a change in the DNA− solvent interaction.…”