AFM‐Based Single Molecule Force Spectroscopy of Polymer Chains: Theoretical Models and Applications

Wei, Hai-Zhen; Ven, Theo G. M. van de

doi:10.1080/05704920701831254

Cited by 18 publications

(15 citation statements)

References 59 publications

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“…From direct comparison of Figures 7a, 7b and 7c , it turns out that the cell is not covered entirely by polysaccharides which are distributed mostly around the cell. To conclude this part, we mention that not only the results are in good agreement with those in AFM literature [21] , [89] , [103] , [104] , but they are also in line with data obtained with other techniques such as FTIR. In addition, to the best of our knowledge, these results provide the first complete large scale physico-chemical analysis ( i.e.…”

Section: Resultssupporting

confidence: 89%

Automated Force Volume Image Processing for Biological Samples

et al. 2011

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Atomic force microscopy (AFM) has now become a powerful technique for investigating on a molecular level, surface forces, nanomechanical properties of deformable particles, biomolecular interactions, kinetics, and dynamic processes. This paper specifically focuses on the analysis of AFM force curves collected on biological systems, in particular, bacteria. The goal is to provide fully automated tools to achieve theoretical interpretation of force curves on the basis of adequate, available physical models. In this respect, we propose two algorithms, one for the processing of approach force curves and another for the quantitative analysis of retraction force curves. In the former, electrostatic interactions prior to contact between AFM probe and bacterium are accounted for and mechanical interactions operating after contact are described in terms of Hertz-Hooke formalism. Retraction force curves are analyzed on the basis of the Freely Jointed Chain model. For both algorithms, the quantitative reconstruction of force curves is based on the robust detection of critical points (jumps, changes of slope or changes of curvature) which mark the transitions between the various relevant interactions taking place between the AFM tip and the studied sample during approach and retraction. Once the key regions of separation distance and indentation are detected, the physical parameters describing the relevant interactions operating in these regions are extracted making use of regression procedure for fitting experiments to theory. The flexibility, accuracy and strength of the algorithms are illustrated with the processing of two force-volume images, which collect a large set of approach and retraction curves measured on a single biological surface. For each force-volume image, several maps are generated, representing the spatial distribution of the searched physical parameters as estimated for each pixel of the force-volume image.

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Section: Resultssupporting

confidence: 89%

Automated Force Volume Image Processing for Biological Samples

et al. 2011

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“…In some SFM measurement schemes the tip apex is of no importance, as, e.g., in experiments on pulling single macromolecules. [20,21] The required here calibration of the elastic properties of the whole cantilever is quite straightforward and rather precise. But in such experiments there is no real imaging, thus, the force measurement by pulling (single-molecule force spectroscopy [22] ) cannot be classified as a microscopy technique.…”

Section: Comparison With Scanning Electron Microscopy (Sem)mentioning

confidence: 99%

Scanning Force Microscopy as Applied to Conformational Studies in Macromolecular Research

Gallyamov

2011

Macromol. Rapid Commun.

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The modern state of SFM research on polymer nano-objects including single chains is discussed in comparison with other similar high-resolution microscopy techniques. The range of problems to be solved preferentially by SFM is highlighted. Promising methodology to describe quantitatively the morphology of macromolecular objects is proposed. The main benefits of this algorithm seem to be the apparent mathematical correctness as well as the possibility to estimate errors and the confidence of the numbers obtained. Special attention is paid to the dynamic observations of conformational transitions on a substrate in real time regime. This approach allows one to realise direct control of the adsorbed macromolecules by means of exposure to different vapours. Driving forces of the vapour-induced reorganisation are discussed.

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“…This model is the most suitable and frequently used to describe the extension of polypeptides. 72,73 The extension z of a macromolecule is related to the retraction force F adh via (eqn (1)):…”

Section: Nanogold Particle Functionalization and Visualizationmentioning

confidence: 99%

The dynamics and pH-dependence of Ag43 adhesins’ self-association probed by atomic force spectroscopy

et al. 2014

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Self-associating auto-transporter (SAAT) adhesins are two-domain cell surface proteins involved in bacteria auto-aggregation and biofilm formation. Antigen 43 (Ag43) is a SAAT adhesin commonly found in Escherichia coli whose variant Ag43a has been shown to promote persistence of uropathogenic E. coli within the bladder. The recent resolution of the tri-dimensional structure of the 499 amino-acids' β-domain in Ag43a has shed light on the possible mechanism governing the self-recognition of SAAT adhesins, in particular the importance of trans-interactions between the L shaped β-helical scaffold of two α-domains of neighboring adhesins. In this study, we use single-molecule force spectroscopy (SMFS) and dynamic force spectroscopy (DFS) to unravel the dynamics of Ag43-self association under various pH and molecular elongation rate conditions that mimic the situations encountered by E. coli in its natural environment. Results evidenced an important stretchability of Ag43α with unfolding of sub-domains leading to molecular extension as long as 150 nm. Nanomechanical analysis of molecular stretching data suggested that self-association of Ag43 can lead to the formation of dimers and tetramers driven by rapid and weak cis- as well as slow but strong trans-interaction forces with a magnitude as large as 100-250 pN. The dynamics of cis- and trans-interactions were demonstrated to be strongly influenced by pH and applied shear force, thus suggesting that environmental conditions can modulate Ag43-mediated aggregation of bacteria at the molecular level.

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AFM‐Based Single Molecule Force Spectroscopy of Polymer Chains: Theoretical Models and Applications

Cited by 18 publications

References 59 publications

Automated Force Volume Image Processing for Biological Samples

Automated Force Volume Image Processing for Biological Samples

Scanning Force Microscopy as Applied to Conformational Studies in Macromolecular Research

The dynamics and pH-dependence of Ag43 adhesins’ self-association probed by atomic force spectroscopy

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