Characterization of Fiber-Forming Peptides and Proteins by Means of Atomic Force Microscopy

Abstract

The atomic force microscope (AFM) is widely used in biological sciences due to its ability to perform imaging experiments at high resolution in a physiological environment, without special sample preparation such as fixation or staining. AFM is unique, in that it allows single molecule information of mechanical properties and molecular recognition to be gathered. This review sets out to identify methodological applications of AFM for characterization of fiber-forming proteins and peptides. The basics of AFM operation are detailed, with in-depth information for any life scientist to get a grasp on AFM capabilities. It also briefly describes antibody recognition imaging and mapping of nanomechanical properties on biological samples. Subsequently, examples of AFM application to fiber-forming natural proteins, and fiber-forming synthetic peptides are given. Here, AFM is used primarily for structural characterization of fibers in combination with other techniques, such as circular dichroism and fluorescence spectroscopy. More recent developments in antibody recognition imaging to identify constituents of protein fibers formed in human disease are explored. This review, as a whole, seeks to encourage the life scientists dealing with protein aggregation phenomena to consider AFM as a part of their research toolkit, by highlighting the manifold capabilities of this technique.

Evaluation of Peptide/Protein Self-Assembly and Aggregation by Spectroscopic Methods

“…Moreover, spectroscopic methods are generally complemented with imaging tools such as Cryo-Transmission, Transmission and Scanning Electron microscopies, as well as Atomic Force and fluorescence microscopies, thus obtaining information about the morphology and topology of the systems [ 21 ]. The description of these valuable methods is not the focus of this review, but considering their relevance in the visualization of self-assembly systems, we encourage the reader to refer to these well-written reviews and books [ 21 , 22 , 23 , 24 , 25 ].…”

Biophysical characteristics of lipid‐induced Aβ oligomers correlate to distinctive phenotypes in transgenic mice

“…The phase analysis describes the energy dissipation and how the tip interacts with the samples by detecting differences in the probe's oscillation in reference to the excitation oscillatory signal, while maintaining a constant amplitude. Physical features that would cause the phase lag to include differences in surface stiffness, viscoelasticity, adhesion, or topographical variations, 62 as we have shown previously. 46,63,64 The data thus derived were further confirmed by the cross-sectional analysis of the oligomers ( Figure 3D,H,L), which is similar to those observed for LFAOs.…”

Overcoming Challenges and Limitations Regarding the Atomic Force Microscopy Imaging and Mechanical Characterization of Nanofibers

“…The leading method for determining the mechanical properties of nanofibers is the AFM nanoindentation method [99,100]. To apply this method, an experiment on a reference stiff material that is not being deformed by the AFM tip is first required [99].…”