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Nanomechanical properties of α-synuclein amyloid fibrils: a comparative study by nanoindentation, harmonic force microscopy, and Peakforce QNM.

Sweers K, van der Werf K, Bennink M, Subramaniam V - Nanoscale Res Lett (2011)

Bottom Line: For nanomechanical measurements, we used single-point nanoindentation, in which the AFM tip as the indenter is moved vertically to the fibril surface and back while the force is being recorded.We also used two recently developed AFM surface property mapping techniques: Harmonic force microscopy (HarmoniX) and Peakforce QNM.We discuss the relative merits of these three methods for the determination of the elastic properties of protein fibrils, particularly considering the differences and difficulties of each method.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nanobiophysics Group, MESA+ Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, Enschede, The Netherlands. k.k.m.sweers@utwente.nl.

ABSTRACT
We report on the use of three different atomic force spectroscopy modalities to determine the nanomechanical properties of amyloid fibrils of the human α-synuclein protein. α-Synuclein forms fibrillar nanostructures of approximately 10 nm diameter and lengths ranging from 100 nm to several microns, which have been associated with Parkinson's disease. Atomic force microscopy (AFM) has been used to image the morphology of these protein fibrils deposited on a flat surface. For nanomechanical measurements, we used single-point nanoindentation, in which the AFM tip as the indenter is moved vertically to the fibril surface and back while the force is being recorded. We also used two recently developed AFM surface property mapping techniques: Harmonic force microscopy (HarmoniX) and Peakforce QNM. These modalities allow extraction of mechanical parameters of the surface with a lateral resolution and speed comparable to tapping-mode AFM imaging. Based on this phenomenological study, the elastic moduli of the α-synuclein fibrils determined using these three different modalities are within the range 1.3-2.1 GPa. We discuss the relative merits of these three methods for the determination of the elastic properties of protein fibrils, particularly considering the differences and difficulties of each method.

No MeSH data available.


Related in: MedlinePlus

Typical force curves. (A) A typical force versus piezo displacement curve obtained from the measurement, with the approach curve (solid red) and the retract curve (dashed blue). (B) Force versus separation approach curve calculated from the force versus piezo displacement curve. (C) Force to the power of 2/3 versus separation approach curve, showing distinct transition from the tip only sensing the fibril (part I) to the part where the tip is sensing the mica under the fibril (part II) until the part where the tip is only pressing on the mica (part III). From the slope of part I, a modulus of elasticity of 1.2 GPa was calculated for the force curve presented here.
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Figure 2: Typical force curves. (A) A typical force versus piezo displacement curve obtained from the measurement, with the approach curve (solid red) and the retract curve (dashed blue). (B) Force versus separation approach curve calculated from the force versus piezo displacement curve. (C) Force to the power of 2/3 versus separation approach curve, showing distinct transition from the tip only sensing the fibril (part I) to the part where the tip is sensing the mica under the fibril (part II) until the part where the tip is only pressing on the mica (part III). From the slope of part I, a modulus of elasticity of 1.2 GPa was calculated for the force curve presented here.

Mentions: We performed nanoindentation experiments on five fibrils, each of which was indented 8 times at different locations along its length. A typical force distance curve resulting from this procedure is shown in Figure 2A. The absence of adhesion during the measurements allowed the use of the Hertz model.


Nanomechanical properties of α-synuclein amyloid fibrils: a comparative study by nanoindentation, harmonic force microscopy, and Peakforce QNM.

Sweers K, van der Werf K, Bennink M, Subramaniam V - Nanoscale Res Lett (2011)

Typical force curves. (A) A typical force versus piezo displacement curve obtained from the measurement, with the approach curve (solid red) and the retract curve (dashed blue). (B) Force versus separation approach curve calculated from the force versus piezo displacement curve. (C) Force to the power of 2/3 versus separation approach curve, showing distinct transition from the tip only sensing the fibril (part I) to the part where the tip is sensing the mica under the fibril (part II) until the part where the tip is only pressing on the mica (part III). From the slope of part I, a modulus of elasticity of 1.2 GPa was calculated for the force curve presented here.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211334&req=5

Figure 2: Typical force curves. (A) A typical force versus piezo displacement curve obtained from the measurement, with the approach curve (solid red) and the retract curve (dashed blue). (B) Force versus separation approach curve calculated from the force versus piezo displacement curve. (C) Force to the power of 2/3 versus separation approach curve, showing distinct transition from the tip only sensing the fibril (part I) to the part where the tip is sensing the mica under the fibril (part II) until the part where the tip is only pressing on the mica (part III). From the slope of part I, a modulus of elasticity of 1.2 GPa was calculated for the force curve presented here.
Mentions: We performed nanoindentation experiments on five fibrils, each of which was indented 8 times at different locations along its length. A typical force distance curve resulting from this procedure is shown in Figure 2A. The absence of adhesion during the measurements allowed the use of the Hertz model.

Bottom Line: For nanomechanical measurements, we used single-point nanoindentation, in which the AFM tip as the indenter is moved vertically to the fibril surface and back while the force is being recorded.We also used two recently developed AFM surface property mapping techniques: Harmonic force microscopy (HarmoniX) and Peakforce QNM.We discuss the relative merits of these three methods for the determination of the elastic properties of protein fibrils, particularly considering the differences and difficulties of each method.

View Article: PubMed Central - HTML - PubMed

Affiliation: Nanobiophysics Group, MESA+ Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, Enschede, The Netherlands. k.k.m.sweers@utwente.nl.

ABSTRACT
We report on the use of three different atomic force spectroscopy modalities to determine the nanomechanical properties of amyloid fibrils of the human α-synuclein protein. α-Synuclein forms fibrillar nanostructures of approximately 10 nm diameter and lengths ranging from 100 nm to several microns, which have been associated with Parkinson's disease. Atomic force microscopy (AFM) has been used to image the morphology of these protein fibrils deposited on a flat surface. For nanomechanical measurements, we used single-point nanoindentation, in which the AFM tip as the indenter is moved vertically to the fibril surface and back while the force is being recorded. We also used two recently developed AFM surface property mapping techniques: Harmonic force microscopy (HarmoniX) and Peakforce QNM. These modalities allow extraction of mechanical parameters of the surface with a lateral resolution and speed comparable to tapping-mode AFM imaging. Based on this phenomenological study, the elastic moduli of the α-synuclein fibrils determined using these three different modalities are within the range 1.3-2.1 GPa. We discuss the relative merits of these three methods for the determination of the elastic properties of protein fibrils, particularly considering the differences and difficulties of each method.

No MeSH data available.


Related in: MedlinePlus