Functional Application Areas

Other Interactions

Lipid Interactions

Lipids are components of cell membranes, are used to make liposomes and other vesicles, and lipids are a source of energy when metabolized. As part of their function, lipids specifically bind to small molecules, drugs, nucleic acids, surfactants, peptides, proteins and other lipids. Knowledge on how lipids interact with other molecules is important to understand how lipids function in biological systems. There have been rapid advances in structural biology and relating structure to biochemical function and mechanism. However, knowledge of lipid structure 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

Biological membranes are very complex systems, and can differ due to composition of fatty acids, charge, pH, etc.  ITC is used to study lipid-drug interactions, as well as lipid-protein and lipid-nucleic acid interactions.  ITC can also be used to characterize solute partitioning of lipid vesicles.

ITC is used to characterize any binding event with a lipid, including:

Surfactant Interactions

Surfactants are amphipathic molecules (have a hydrophilic part and a hydrophobic part).These can be cationic, anionic, zwitterionic or non-ionic. Surfactants form micelles when the concentration goes above its CMC (critical micelle concentration).  Surfactants are additives to solubilize membrane preparations, and are used to make consumer products like shampoo and detergent.  Surfactants are also used as part of drug delivery systems. ITC is used to study the CMC of surfactant solutions, as well as the interaction of surfactants with membranes, proteins and other biomolecules.

Surfactant Interactions

Other Interactions

Since ITC is label-free, has no molecular weight limitations, and can be used in a wide range of buffers, pHs, and ionic strengths, it can be used to measure affinities and thermodynamics of a wide range of interactions, involving:

  • Drug-metal binding
  • Drug-drug binding
  • Ion-ion binding
  • Cyclodextrin-guest binding
  • Polymers
  • Nanoparticles

Non-Biological Interactions

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