Microscale Thermophoresis to Study Protein-Lipid Interactions in Solution

To study the interaction of proteins with lipid molecules, begin with two capillary tubes. Add fluorescent dye-labeled test proteins in both tubes and unlabeled lipid molecules to one of them. Place these capillaries in an array and place them inside a microscale thermophoresis instrument.

Irradiate the protein-containing capillary with focused infrared light, creating a temperature rise in the focal spot that diffuses through the solution, generating a temperature gradient within a narrow region containing fluorescently-labeled proteins.

The fluorescence detector collects the fluorescence signal from the same spot of the capillary — where the laser is focused. The processor converts the signal and generates a plot of the relative fluorescence as a function of time.

In a temperature gradient, labeled proteins start migrating from the hotter region to the cooler region, exhibiting thermophoresis — a phenomenon of temperature-dependent migration.

Due to thermophoresis, the fluorescence intensity gradually decreases over time and attains a steady state, where labeled proteins reach equilibration.

Irradiate the protein-lipid mix-containing capillary, creating a temperature gradient.

During thermophoresis, the migrating labeled proteins interact with the lipid molecules, forming lipid-protein complexes with higher molecular masses. This leads to retardation of their movement.

This differential migration causes a shift in fluorescence, confirming successful protein-lipid interaction.