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Atomic Force Microscopy (AFM) is a powerful tool for imaging and studying surface properties of materials as well as probing molecular interactions at an atomic resolution. AFM is comprised of a cantilever-tip assembly that raster scans across the sample surface using a piezoelectric tube controlled by a computer. The deflection of the cantilever is monitored using an optical detection system in the form of a laser that reflects off the back of the cantilever and onto a four-quadrant photodiode while scanning. A feedback loop maintains a constant tip-sample force or interaction.
Atomic Force Microscopy (AFM) is a powerful tool for imaging and studying surface properties of materials as well as probing molecular interactions at an atomic resolution. AFM is comprised of a cantilever-tip assembly that raster scans across the sample surface using a piezoelectric tube controlled by a computer. The deflection of the cantilever is monitored using an optical detection system in the form of a laser that reflects off the back of the cantilever and onto a four-quadrant photodiode while scanning. A feedback loop maintains a constant tip-sample force or interaction.
Force spectroscopy technique is a remarkable feature for the AFM. Through force-distance curves, the interaction between the cantilever tip and the sample can be detected. When the cantilever approaches the sample, the indentation (cantilever deflection) remains zero until making a physical contact with the sample surface (at zero on the x-axis). The cantilever keeps indenting into the sample until the deflection reaches a target depth called set-point. Then AFM pulls the cantilever away from the sample. During this process, the cantilever deflection is recorded as a function of its location. In general, the raw data by AFM represents the dependence between the electrical signal, which is proportional to the cantilever deflection and transformed to force, and the vertical location of the cantilever which is converted into a tip-sample distance. The calibration of the spring constant and deflection sensitivity are required for the conversion.
Force spectroscopy technique is a remarkable feature for the AFM. Through force-distance curves, the interaction between the cantilever tip and the sample can be detected. When the cantilever approaches the sample, the indentation (cantilever deflection) remains zero until making a physical contact with the sample surface (at zero on the x-axis). The cantilever keeps indenting into the sample until the deflection reaches a target depth called set-point. Then AFM pulls the cantilever away from the sample. During this process, the cantilever deflection is recorded as a function of its location. In general, the raw data by AFM represents the dependence between the electrical signal, which is proportional to the cantilever deflection and transformed to force, and the vertical location of the cantilever which is converted into a tip-sample distance. The calibration of the spring constant and deflection sensitivity are required for the conversion.
By scanning the sample surface (e.g., cancer cells) with the tip functionalized with a ligand, the specific recognition information between ligand and cell receptor can be rapidly detected and acquired.
By scanning the sample surface (e.g., cancer cells) with the tip functionalized with a ligand, the specific recognition information between ligand and cell receptor can be rapidly detected and acquired.
During tip retracting in the force-distance curve, the ligand from a complex with the receptor leads to a force signal of distinct shape. The force increases until dissociation occurs (red circle) at the unbinding force (fu).
During tip retracting in the force-distance curve, the ligand from a complex with the receptor leads to a force signal of distinct shape. The force increases until dissociation occurs (red circle) at the unbinding force (fu).
The binding force between individual ligand and cell receptor was measured using single-molecule force spectroscopy.
The binding force between individual ligand and cell receptor was measured using single-molecule force spectroscopy.
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