Dissipative Microgravimetry Technique to Study Protein-Lipid Bilayer Interaction

To study the interaction between a phospholipid-binding protein and a lipid bilayer through dissipative microgravimetry, take a microbalance with a quartz sensor. Upon applying a suitable voltage, the quartz layer — sandwiched between two metal electrodes — oscillates at a specific frequency.

Add a suspension of small unilamellar vesicles — consisting of a single lipid bilayer — onto the sensor. The vesicles adsorb on the silica-coated hydrophilic surface — increasing the sensor mass and proportionally decreasing its oscillation frequency.

The buffer-filled vesicles act as a viscoelastic layer, leading to dissipation — the dampening of the oscillation. The adsorbed vesicles rupture, releasing the enclosed buffer. The resultant decrease in mass increases the oscillation frequency.

The ruptured vesicles form a continuous bilayer, mimicking a biological membrane. The rigidity of the bilayer decreases the dissipation.

Add a buffer containing calcium ions, along with the target protein. The calcium ions bind to the protein and change its conformation — enabling binding to the lipid molecules in the bilayer.

Protein binding increases the mass of the sensor — leading to a decreased freque