Adsorption Thermodynamics of Short-Chain Peptides on Charged and Uncharged Nanothin Polymer Films

Singh, Namrata; Husson, Scott M.

doi:10.1021/la0533765

Cited by 17 publications

(18 citation statements)

References 38 publications

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“…The resultant adsorption free energy of about A ϭ 5 kJ/mol per monomer in process II is quite close to the value of A ϭ 3.6 kJ/mol for phenylalanine as measured by adsorption isotherm analysis (18). For both processes I and II the water-water and peptide-surface contributions to the internal energy, U WW and U PS , are positive and larger than the resulting total energy U and free energy A.…”

Section: Discussionsupporting

confidence: 76%

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.

152

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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Section: Discussionsupporting

confidence: 76%

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.

152

179

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“…Two lines are indicated in this figure: a solid line that represents the best fit linear regression line (R 2 =0.98) comparing the two sets of data and a dashed line that indicates what the regression line should be for perfect agreement between these two data sets with R 2=1.0. A Student’s t–test analysis based on the 9 peptide-SAM surface combinations tested (3 measurements for each), at the 5% level of significance (α = 0.05) comparing these lines does not indicate a significant difference between their slope (p value = 0.089) or their y-axis intercept (p value = 0.27).…”

Section: Resultsmentioning

confidence: 99%

“…should be accounted for. From a standard SPR analysis, an adsorption model, such as the Langmuir model, is generally used to calculate Δ G° ads on the basis of the overall shape of the adsorption isotherm 2, 26–27. This, however, creates complications because solute–solute interactions may occur on the surface as the surface sites become filled, which can substantially influence the shape of the isotherm and invalidate the application of the Langmuir adsorption model 1.…”

Section: Experimental Methodsmentioning

confidence: 99%

Correlation between Desorption Force Measured by Atomic Force Microscopy and Adsorption Free Energy Measured by Surface Plasmon Resonance Spectroscopy for Peptide−Surface Interactions

Wei¹,

Latour²

2010

Langmuir

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Surface Plasmon resonance (SPR) spectroscopy is a useful technique for thermodynamically characterizing peptide-surface interactions; however, its usefulness is limited to the types of surfaces that can readily be formed as thin layers in nanometer scale on metallic biosensor substrates. Atomic force microscopy (AFM), on the other hand, can be used with any microscopically flat surface, thus making it more versatile for studying peptide-surface interactions. AFM, however, has the drawback of data interpretation due to questions regarding peptide-to-probe-tip density. This problem could be overcome if results from a standardized AFM method could be correlated with SPR results for a similar set of peptide-surface interactions so that AFM studies using the standardized method could be extended to characterize peptide-surface interactions for surfaces that are not amenable for characterization by SPR. In this paper, we present the development and application of an AFM method to measure adsorption forces for host-guest peptides sequence on surfaces consisting of alkanethiol self-assembled monolayers (SAMs) with different functionality. The results from these studies show that a linear correlation exists between these data and the adsorption free energy (ΔG°a ds ) values associated with a similar set of peptide-surface systems available from SPR measurements. These methods will be extremely useful to thermodynamically characterize the adsorption behavior for peptides on a much broader range of surfaces than can be used with SPR to provide information related to understanding protein adsorption behavior to these surfaces and to provide an experimental database that can be used for the evaluation, modification, and validation of force field parameters that are needed to accurately represent protein adsorption behavior for molecular simulations.

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“…On surfaces, however, the binding free energy of a peptide is more difficult to determine. On electrically conductive surfaces, SPR is a common technique to observe and measure peptide adsorption [65,80,81]. For surfaces with more than a nanometre-thick non-conductive layer such as organic polymers, Thyparambil et al have measured peptide binding by determining a correlation between desorption via atomic force microscopy and the binding free energy from SPR experiments.…”

Section: Experimental Target Data and Validation Datamentioning

confidence: 99%

Force fields for simulating the interaction of surfaces with biological molecules

et al. 2016

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The interaction of biomolecules with solid interfaces is of fundamental importance to several emerging biotechnologies such as medical implants, anti-fouling coatings and novel diagnostic devices. Many of these technologies rely on the binding of peptides to a solid surface, but a full understanding of the mechanism of binding, as well as the effect on the conformation of adsorbed peptides, is beyond the resolution of current experimental techniques. Nanoscale simulations using molecular mechanics offer potential insights into these processes. However, most models at this scale have been developed for aqueous peptide and protein simulation, and there are no proven models for describing biointerfaces. In this review, we detail the current research towards developing a non-polarizable molecular model for peptide-surface interactions, with a particular focus on fitting the model parameters as well as validation by choice of appropriate experimental data.

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Adsorption Thermodynamics of Short-Chain Peptides on Charged and Uncharged Nanothin Polymer Films

Cited by 17 publications

References 38 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

Correlation between Desorption Force Measured by Atomic Force Microscopy and Adsorption Free Energy Measured by Surface Plasmon Resonance Spectroscopy for Peptide−Surface Interactions

Force fields for simulating the interaction of surfaces with biological molecules

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