Detachment of a single polyelectrolyte chain adsorbed on a charged surface

Châtellier, Xavier; Senden, Tim J.; Joanny, Jean‐François; Meglio, J.-M. di

doi:10.1209/epl/i1998-00147-6

Cited by 114 publications

(105 citation statements)

References 14 publications

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“…2 we demonstrate that the observed plateau force is independent of the pulling rate and the pulling direction. This observation points to a high mobility of the peptide on the diamond surface and implies that the adsorbed chain section reaches equilibrium on the experimental time scales (15)(16)(17). Our measurement thus corresponds to a high-precision determination of the equilibrium HA between a single peptide chain and a hydrophobic substrate.…”

mentioning

confidence: 66%

Peptide adsorption on a hydrophobic surface results from an interplay of solvation, surface, and intrapeptide forces

Horinek

Serr²,

Geisler³

et al. 2008

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

151

179

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The hydrophobic effect, i.e., the poor solvation of nonpolar parts of molecules, plays a key role in protein folding and more generally for molecular self-assembly and aggregation in aqueous media. The perturbation of the water structure accounts for many aspects of protein hydrophobicity. However, to what extent the dispersion interaction between molecular entities themselves contributes has remained unclear. This is so because in peptide folding interactions and structural changes occur on all length scales and make disentangling various contributions impossible. We address this issue both experimentally and theoretically by looking at the force necessary to peel a mildly hydrophobic single peptide molecule from a flat hydrophobic diamond surface in the presence of water. This setup avoids problems caused by bubble adsorption, cavitation, and slow equilibration that complicate the much-studied geometry with two macroscopic surfaces. Using atomic-force spectroscopy, we determine the mean desorption force of a single spider-silk peptide chain as F ‫؍‬ 58 ؎ 8 pN, which corresponds to a desorption free energy of Ϸ5 kBT per amino acid. Our all-atomistic molecular dynamics simulation including explicit water correspondingly yields the desorption force F ‫؍‬ 54 ؎ 15 pN. This observation demonstrates that standard nonpolarizable force fields used in classical simulations are capable of resolving the fine details of the hydrophobic attraction of peptides. The analysis of the involved energetics shows that water-structure effects and dispersive interactions give contributions of comparable magnitude that largely cancel out. It follows that the correct modeling of peptide hydrophobicity must take the intimate coupling of solvation and dispersive effects into account.atomic-force microscopy ͉ hydrophobic effect ͉ molecular dynamics simulation ͉ single molecules ͉ protein adsorption F or scientists working with biological or soft matter systems, understanding what holds the world together largely means unraveling the mechanism behind the so-called hydrophobic effect. The term hydrophobic attraction (HA) was initially introduced to describe the attraction between small nonpolar molecules such as methane in water (1, 2). It is nowadays more broadly used to describe forces between all kinds of nonpolar objects in aqueous environments, implying a common mechanism for protein folding, micellization, self-assembly of lipids, oil-water demixing, and thus any supermolecular aggregation in water (3). For predicting protein structures and function the magnitude and nature of the HA acting between peptide segments is a central issue that has not been fully resolved. Much effort was put in force measurements between well defined model systems, for example mica surfaces made hydrophobic or micrometer-sized plastic beads. However, these systems are notoriously plagued by secondary effects, such as bubble adsorption and cavitation effects (4, 5) or compositional rearrangements (6). In simulations of interacting planar plates, similar eff...

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mentioning

confidence: 66%

Peptide adsorption on a hydrophobic surface results from an interplay of solvation, surface, and intrapeptide forces

Horinek

Serr²,

Geisler³

et al. 2008

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

151

179

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“…Such adhesion is referred to as 'plateau forces' and commonly observed for polyelectrolyte chain desorption from a surface, much like a polymer chain being 'peeled' off the surface. Plateau forces arise due to dependencies on the dissociation rate of repeating polymer chain-surface bonds relative to the rate at which the chain is pulled from the surface and presence of oppositely charged surfaces 34,35 . In contrast to the interactions involving multiple rupture peaks (Fig.…”

Section: Resultsmentioning

confidence: 99%

Quantifying fibronectin adhesion with nanoscale spatial resolution on glycosaminoglycan doped polypyrrole using Atomic Force Microscopy

Gelmi

Higgins

Wallace

2013

Biochimica et Biophysica Acta (BBA) - General Subjects

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The interaction of ECM proteins is critical in determining the performance of materials used in biomedical applications such as tissue regeneration, implantable bionics and biosensing. Methods: To improve our understanding of ECM protein-conducting polymer interactions, we have used Atomic Force Microscopy (AFM) to elucidate the interactions of fibronectin (FN) on polypyrrole (PPy) doped with different glycosaminoglycans. Results: We were able to classify four main types of FN interactions, including those related to 1) non-specific adhesion, 2) protein unfolding and subsequent unbinding from the surface, 3) desorption and 4) interactions with no adhesion. FN adhesion on PPy/hyaluronic acid showed a significantly lower density of surface adhesion with the adhesion restricted to nodule structures, as opposed to their peripheries, of the polymer morphology. In contrast, PPy/chondroitin sulfate showed a significantly higher density of surface adhesion to the point where the distribution of adhesion effectively masked the topography. Through conductive AFM imaging, we found that the conductive regions correlated with regions of FN adhesion. Conclusions: Given that the conductivity requires doping of the polymer, these findings suggest that FN adhesion is mediated by interactions with chondroitin sulfate and hyaluronic acid at the polymer surface and may be indicative of specific interactions due to contributions from electrostatic attraction between the FN and sulfate/anionic groups of the dopants. General significance: This study demonstrates the ability of AFM to resolve the protein-conducting polymer interactions at the molecular and nanoscale level, which will be important for interfacing these polymer materials with biological systems. This article is part of a Special Issue entitled Organic Bioelectronics -Novel Applications in Biomedicine.

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“…(38) represents an exact solution to our single degree of freedom model. We are interested primarily in the distribution ofZ for large m, so we would like to integrate over all E and then take the limit m → ∞.…”

Section: Disorder-averaged Behaviormentioning

confidence: 99%

Single molecule statistics and the polynucleotide unzipping transition

2002

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We present an extensive theoretical investigation of the mechanical unzipping of double-stranded DNA under the influence of an applied force. In the limit of long polymers, there is a thermodynamic unzipping transition at a critical force value of order 10 pN, with different critical behavior for homopolymers and for random heteropolymers. We extend results on the disorder-averaged behavior of DNA's with random sequences [1] to the more experimentally accessible problem of unzipping a single DNA molecule. As the applied force approaches the critical value, the double-stranded DNA unravels in a series of discrete, sequence-dependent steps that allow it to reach successively deeper energy minima. Plots of extension versus force thus take the striking form of a series of plateaus separated by sharp jumps. Similar qualitative features should reappear in micromanipulation experiments on proteins and on folded RNA molecules. Despite their unusual form, the extension versus force curves for single molecules still reveal remnants of the disorder-averaged critical behavior. Above the transition, the dynamics of the unzipping fork is related to that of a particle diffusing in a random force field; anomalous, disorder-dominated behavior is expected until the applied force exceeds the critical value for unzipping by roughly 5 pN.

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Detachment of a single polyelectrolyte chain adsorbed on a charged surface

Cited by 114 publications

References 14 publications

Peptide adsorption on a hydrophobic surface results from an interplay of solvation, surface, and intrapeptide forces

Peptide adsorption on a hydrophobic surface results from an interplay of solvation, surface, and intrapeptide forces

Quantifying fibronectin adhesion with nanoscale spatial resolution on glycosaminoglycan doped polypyrrole using Atomic Force Microscopy

Single molecule statistics and the polynucleotide unzipping transition

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