Functional Application Areas

Nucleic Acid-Lipid Interactions

Lipids and liposomes are used as delivery systems for oligonuclotides and DNA into host cells, as a gene transfection system for protein engineering and expression. Understanding how lipids and DNA interact with each other, as well as cell membranes, is important to optimizing cell transfection.

There have been rapid advances in structural biology and relating structure to biochemical function and mechanism. However, knowledge of lipid and nucleic acid structures alone does not ensure accurate prediction of function and biological activity. The complete characterization of any binding interaction requires a quantification of the affinity, number of binding sites, and the thermodynamics. 

Thermodynamic data, specifically enthalpy (ΔH) and entropy (ΔS), reveal the forces that drive complex formation and mechanism of action. Thermodynamics provide information on conformational changes, hydrogen bonding, hydrophobic interactions, and charge-charge interactions.  This information is used to describe the function and mechanism at a molecular level. 

Isothermal Titration Calorimetry (ITC) is a powerful analytical tool which measures the binding affinity and thermodynamics between any two biomolecules. ITC is considered the “gold standard” assay for binding

Since ITC is done in-solution, it can utilize any biological buffer, and can be performed in the presence of detergents. For a full characterization of a biomolecular interaction, it is important to observe how salt, pH, temperature, etc affects binding affinity and thermodynamics.

ITC has been used to characterize lipid-DNA interactions, in order to develop gene transfection systems with greater efficacy. 

References

Isothermal titration calorimetric analysis of the interaction between cationic lipids and plasmid DNA.
Lobo B. A., Davis A., Koe G., Smith J. G., and Middaugh C. R.
Arch Biochem Biophys 386, 95-105 (2001)

Thermodynamics of cationic lipid binding to DNA and DNA condensation: roles of electrostatics and hydrophobicity.
Matulis D., Rouzina I., and Bloomfield V. A.
J Am Chem Soc 124, 7331-7342 (2002)

ITC – Nucleic Acid-Lipid Interactions Reference List

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