Single-molecule force spectroscopy on polysaccharides by AFM – nanomechanical fingerprint of α-(1,4)-linked polysaccharides

Li, Hongbin; Rief, Matthias; Oesterhelt, Filipp; Gaub, Hermann E.; Zhang, Xi; Shen, Jiacong

doi:10.1016/s0009-2614(99)00389-9

Cited by 137 publications

(154 citation statements)

References 25 publications

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“…1. As described elsewhere, 14,18,[30][31][32][33] the characteristic plateau at 0.3 nN, which is caused by the chair-boat transition of CMA, can be used to confirm that a single molecule has been stretched. At the end of the plateau in Fig.…”

Section: Resultsmentioning

confidence: 99%

Mechanically activated rupture of single covalent bonds: evidence of force induced bond hydrolysis

Schmidt

Kersch

Beyer

et al. 2011

Phys. Chem. Chem. Phys.

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We have used temperature-dependent single molecule force spectroscopy to stretch covalently anchored carboxymethylated amylose (CMA) polymers attached to an amino-functionalized AFM cantilever. Using an Arrhenius kinetics model based on a Morse potential as a one-dimensional representation of covalent bonds, we have extracted kinetic and structural parameters of the bond rupture process. With 35.5 kJ mol À1 , we found a significantly smaller dissociation energy and with 9.0 Â 10 2 s À1 to 3.6 Â 10 3 s À1 also smaller Arrhenius pre-factors than expected for homolytic bond scission. One possible explanation for the severely reduced dissociation energy and Arrhenius pre-factors is the mechanically activated hydrolysis of covalent bonds. Both the carboxylic acid amide and the siloxane bond in the amino-silane surface linker are in principle prone to bond hydrolysis. Scattering, slope and curvature of the scattered data plots indicate that in fact two competing rupture mechanisms are observed.

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Section: Resultsmentioning

confidence: 99%

Mechanically activated rupture of single covalent bonds: evidence of force induced bond hydrolysis

Schmidt

Kersch

Beyer

et al. 2011

Phys. Chem. Chem. Phys.

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“…Our experiments enhance the ability of single-molecule force spectroscopy to make high-resolution measurements of the conformations of single polysaccharide molecules under a stretching force, making an important addition to polysaccharide spectroscopy. S ingle molecule force spectroscopy has become an important tool to examine the conformations of proteins and polysaccharide molecules under a stretching force (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). Recent experiments have demonstrated that a force field can trigger conformational changes in these molecules that cannot be observed by traditional NMR or x-ray crystallographic techniques.…”

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confidence: 99%

“…Recent experiments have demonstrated that a force field can trigger conformational changes in these molecules that cannot be observed by traditional NMR or x-ray crystallographic techniques. Force spectroscopy involves measuring the force required to extend a molecule by a certain amount (2)(3)(4)(5)(6)(7)(8)(9)(10). The data are compiled into a forceextension relationship that gives a characteristic fingerprint for the conformational transitions of the molecule under study.…”

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confidence: 99%

“…In the most typical atomic force microscopy (AFM) experiment, a single molecule adsorbed between a substrate and the cantilever tip is extended vertically at a constant rate while the resulting force is measured (2)(3)(4)(5)(6)(7)(8)(9)(10). Although it may seem that these experiments can be completed equally by controlling either the extension or the force applied to the molecule, these two modes can yield quite different results (e.g., see ref.…”

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Chair-boat transitions in single polysaccharide molecules observed with force-ramp AFM

Marszałek

Oberhauser

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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136

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Under a stretching force, the sugar ring of polysaccharide molecules switches from the chair to the boat-like or inverted chair conformation. This conformational change can be observed by stretching single polysaccharide molecules with an atomic force microscope. In those early experiments, the molecules were stretched at a constant rate while the resulting force changed over wide ranges. However, because the rings undergo force-dependent transitions, an experimental arrangement where the force is the free variable introduces an undesirable level of complexity in the results. Here we demonstrate the use of force-ramp atomic force microscopy to capture the conformational changes in single polysaccharide molecules. Force-ramp atomic force microscopy readily captures the ring transitions under conditions where the entropic elasticity of the molecule is separated from its conformational transitions, enabling a quantitative analysis of the data with a simple two-state model. This analysis directly provides the physico-chemical characteristics of the ring transitions such as the width of the energy barrier, the relative energy of the conformers, and their enthalpic elasticity. Our experiments enhance the ability of single-molecule force spectroscopy to make high-resolution measurements of the conformations of single polysaccharide molecules under a stretching force, making an important addition to polysaccharide spectroscopy. S ingle molecule force spectroscopy has become an important tool to examine the conformations of proteins and polysaccharide molecules under a stretching force (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). Recent experiments have demonstrated that a force field can trigger conformational changes in these molecules that cannot be observed by traditional NMR or x-ray crystallographic techniques. Force spectroscopy involves measuring the force required to extend a molecule by a certain amount (2-10). The data are compiled into a forceextension relationship that gives a characteristic fingerprint for the conformational transitions of the molecule under study. For example, force-extension relationships of polysaccharides such as amylose and dextran (13, 14) display a characteristic plateau (2, 4) that marks forced transitions of the glucose monomers from their chair conformation to the boat-like conformation (4). Similarly, two distinct plateaus in the force-extension curve of pectin (13, 14) report a transition of the galactose rings from the chair conformation to the boat conformation and a subsequent flip of the boat to the inverted chair conformation (5). These observations provide an interesting perspective on the behavior of polysaccharides under mechanical tension (15) and suggest that fingerprints of forced conformational transitions can be used as a means for identifying single polysaccharides molecules in solution (9).In the most typical atomic force microscopy (AFM) experiment, a single molecule adsorbed between a substrate and the cantilever tip is extended vertically at a constant rate while t...

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“…Application of a force of Ϸ200 pN to polymers of ␣-D-glucopyranose such as amylose drives a conformational change in the pyranose ring that is evident as a sudden elongation of the molecule, marking a prominent enthalpic component of the elasticity of the molecule (2,10). This enthalpic component results from an increase in the distance between glycosidic oxygen atoms caused by a forceinduced transition between the chair and boat conformations of the pyranose ring (2,11). The glycosidic bonds of amylose are disposed in the C1-O1 [axial (a)] and C4-O4 [equatorial (e)] configuration.…”

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Atomic levers control pyranose ring conformations

Marszałek

Pang

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

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150

167

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Atomic force microscope manipulations of single polysaccharide molecules have recently expanded conformational chemistry to include force-driven transitions between the chair and boat conformers of the pyranose ring structure. We now expand these observations to include chair inversion, a common phenomenon in the conformational chemistry of six-membered ring molecules. We demonstrate that by stretching single pectin molecules (1 3 4-linked ␣-D-galactouronic acid polymer), we could change the pyranose ring conformation from a chair to a boat and then to an inverted chair in a clearly resolved two-step conversion: 4 C 1 i boat i 1 C 4 . The two-step extension of the distance between the glycosidic oxygen atoms O 1 and O 4 determined by atomic force microscope manipulations is corroborated by ab initio calculations of the increase in length of the residue vector O 1 O 4 on chair inversion. We postulate that this conformational change results from the torque generated by the glycosidic bonds when a force is applied to the pectin molecule. Hence, the glycosidic bonds act as mechanical levers, driving the conformational transitions of the pyranose ring. When the glycosidic bonds are equatorial (e), the torque is zero, causing no conformational change. However, when the glycosidic bond is axial (a), torque is generated, causing a rotation around COC bonds and a conformational change. This hypothesis readily predicts the number of transitions observed in pyranose monomers with 1a-4a linkages (two), 1a-4e (one), and 1e-4e (none). Our results demonstrate single-molecule mechanochemistry with the capability of resolving complex conformational transitions.Atomic force microscope (AFM) manipulations of single polysaccharide molecules have recently expanded conformational chemistry (1) to include force-driven transitions between the chair and boat conformers of the pyranose ring structure (2). The application of a force to a single molecule will deform it elastically and also induce conformational transitions. Although it is easy to understand the origin of an elastic deformation, the mechanics of the conformational transition is less clear.Pyranose-based sugars have two distinct chair conformations, 4 C 1 and 1 C 4 (3), separated by an energy barrier of Ϸ11 kcal͞mol (4). In addition to the chair conformers, pyranoses have intermediate conformers corresponding to the boat conformation, whose energy is Ϸ5-8 kcal͞mol above the energy of the 4 C 1 chair (5). Thermally driven transitions do occur between these conformers. However, in the absence of an applied force, the most stable conformation of a pyranose is that of the 4 C 1 chair (4-9). Application of a force of Ϸ200 pN to polymers of ␣-D-glucopyranose such as amylose drives a conformational change in the pyranose ring that is evident as a sudden elongation of the molecule, marking a prominent enthalpic component of the elasticity of the molecule (2, 10). This enthalpic component results from an increase in the distance between glycosidic oxygen atoms caused by a for...

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Single-molecule force spectroscopy on polysaccharides by AFM – nanomechanical fingerprint of α-(1,4)-linked polysaccharides

Cited by 137 publications

References 25 publications

Mechanically activated rupture of single covalent bonds: evidence of force induced bond hydrolysis

Mechanically activated rupture of single covalent bonds: evidence of force induced bond hydrolysis

Chair-boat transitions in single polysaccharide molecules observed with force-ramp AFM

Atomic levers control pyranose ring conformations

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