Related Experiment Video
Updated: May 28, 2026
08:30
Gene-therapy Inspired Polycation Coating for Protection of DNA Origami Nanostructures
Published on: January 19, 2019
The ionic strength effect on the DNA complexation by DOPC - gemini surfactants liposomes
Petra Pullmannová1, Margarida Bastos, Guangyue Bai
1Department of Physical Chemistry, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, SK-812 37 Bratislava, Slovakia. pullmannova@fpharm.uniba.sk
Biophysical Chemistry
|October 15, 2011
Summary
Gemini surfactants and DOPC lipids form DNA complexes with a condensed lamellar phase (L(α)(c)). Phase separation into a coexisting lamellar phase (L(B)) depends on ionic strength and preparation, impacting DNA binding.
Area of Science:
- Materials Science
- Biophysics
- Physical Chemistry
Background:
- Cationic liposomes, formed from gemini surfactants and DOPC, are investigated for DNA complexation.
- Understanding the structural organization of these complexes is crucial for gene delivery applications.
Purpose of the Study:
- To characterize the microstructure of DNA-gemini surfactant-DOPC complexes.
- To investigate the influence of ionic strength and preparation methods on complex formation and phase behavior.
- To elucidate the role of surface charge density and ionic strength in DNA binding.
Main Methods:
- Small-angle X-ray diffraction (SAXD) and small-angle neutron scattering (SANS) for structural analysis.
- Isothermal titration calorimetry (ITC) to study complex formation thermodynamics.
- Zeta potential measurements to assess surface charge characteristics.
Main Results:
- DNA-liposome complexes exhibit a condensed lamellar phase (L(α)(c)) with a regular inner microstructure.
- A secondary lamellar phase (L(B)) coexists, with periodicities dependent on ionic strength (50-200mM NaCl).
- Phase separation is influenced by liposome surface charge density, ionic strength, and preparation method.
- High ionic strength decreases DNA binding and shifts the isoelectric point to lower DNA/gemini surfactant ratios.
Conclusions:
- The structural organization of DNA-gemini surfactant complexes is sensitive to ionic strength and preparation.
- Phase separation phenomena play a significant role in the stability and DNA binding capacity of these liposomal systems.
- Ionic strength modulates the effective charge and binding stoichiometry of the complexes, impacting their potential as gene delivery vectors.
Related Concept Videos
01:12Ionic Strength: Overview
The ionic strength of a solution is a quantitative way of expressing the total electrolyte concentration of a solution. This concept was first introduced in 1921 by two American physical chemists, Gilbert N. Lewis and Merle Randall, while describing the activity coefficient of strong electrolytes. During the calculation of ionic strength (I or μ), all the cations and anions are considered. However, the concentration (c) of an ion with a greater charge number (z) has a greater contribution to...
03:13Intermolecular Forces
Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions (attractive or repulsive) between charged species (permanent, partial, or temporary charges) and exist with varying strengths between ions, polar, nonpolar, and neutral molecules. The different types of intermolecular forces are ion–dipole, dipole–dipole, hydrogen bonds, and dispersion; among these, dipole–dipole, hydrogen bonds, and dispersion...
01:19Ionic Strength: Effects on Chemical Equilibria
The addition of an inert ionic compound increases the solubility of a sparingly soluble salt. For example, adding potassium nitrate to a saturated solution of calcium sulfate significantly enhances the solubility of calcium sulfate. Le Châtelier's principle cannot predict this shift in the equilibrium. Instead, this could be explained in terms of changes in the effective concentration of the ions in solution in the presence of added inert salt.
In this solution, the primary cation—the calcium...
In this solution, the primary cation—the calcium...
01:17Factors Affecting Activity Coefficient
The extended Debye-Hückel equation indicates that the activity coefficient of an ion in an aqueous solution at 25°C depends on three partially interdependent properties: the ionic strength of the solution, the charge of the ion, and the ion size.
The activity coefficient value for an ion is close to one when the solution has almost zero ionic strength, i.e., when the solution shows close to ideal behavior. As the ionic strength of the solution increases from 0 to 0.1 mol/L, a decrease in the...
The activity coefficient value for an ion is close to one when the solution has almost zero ionic strength, i.e., when the solution shows close to ideal behavior. As the ionic strength of the solution increases from 0 to 0.1 mol/L, a decrease in the...
01:19Complexation Equilibria: The Chelate Effect
In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...
02:55Solubility of Ionic Compounds
Solubility is the measure of the maximum amount of solute that can be dissolved in a given quantity of solvent at a given temperature and pressure. Solubility is usually measured in molarity (M) or moles per liter (mol/L). A compound is termed soluble if it dissolves in water.