Thermodynamic Measurements and Predictions of the Adsorption of Short-Chain Peptides on Nanothin Polymer Films

Abstract

This contribution describes experimental measurements of submolecular-level interaction energies involved in the process of peptide adsorption on polymer films. The objective of this study was to use surface plasmon resonance (SPR) spectroscopy to measure the Gibbs energy change on adsorption (DeltaG(ad)) for pairs of various homopeptides on highly uniform, nanothin polymer films and to use these data, along with the principle of additivity, to predict DeltaG(ad) for homologous homopeptides, as well as for a mixed-residue peptide. By using a graft polymerization methodology, a nanothin poly(2-vinylpyridine) film was prepared and adsorption energies were measured first for a homologous series of tyrosine (Y) homopeptides on this film to determine submolecular-level interaction energies. By using SPR, adsorption isotherms were measured for YY and YYY peptides; analysis of these isotherms provided DeltaG(ad) data for a midchain tyrosine unit and a set of chain-end tyrosine units; values were -0.75 +/- 0.07 kcal/mol and -2.12 +/- 0.04 kcal/mol, respectively. Combining the thermodynamic contributions for adsorption of individual tyrosine units allowed a predictive estimate of -5.12 +/- 0.32 kcal/mol for the adsorption energy for YYYYYY; this estimate deviated by only 2.3% from its measured value of -5.24 +/- 0.06 kcal/mol. Similarly, adsorption energies were found for phenylalanine, glycine, and tyrosine-leucine peptides. Combining the thermodynamic contributions for adsorption of individual residue units allowed a predictive estimate of -3.24 +/- 0.38 kcal/mol for a pentapeptide, leucine enkephalin; this estimate deviated by only 3.0% from its measured value of -3.34 +/-0.11 kcal/mol.

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

“…The SPR analysis methods allowed us to check whether adsorption hysteresis existed and to what extent, if any, were the model short-chain peptides bound irreversibly to the surface over the time frame of the experiments. On the basis of results here and previously, , adsorption hysteresis appears to be minimal for these systems under the low activity conditions used to extract thermodynamic adsorption data. Thus, as we show, the use of reversible thermodynamic principles seems justified for these systems.…”

“…Leucine enkephalin was chosen because of its medicinal interest, as well as its well-characterized structure. We have discussed these features in our previous communication . Of special interest to our present study, leucine enkephalin lacks a secondary structure.…”

“…Curved lines represent predictions for YYYY ( ) and YYYYY (− − −). Reproduced from Singh and Husson

4 Adsorption isotherms for phenylalanine peptides (2, 3, and 4 units) adsorbing on the PVP surface at 25 °C from pH 7 HEPES buffer solutions.

5 Adsorption isotherms for glycine peptides (4, 5, and 6 units) adsorbing on the PVP surface at 25 °C from pH 7 HEPES buffer solutions.

6 Adsorption isotherms for tyrosine peptides (2, 3, and 6 units) adsorbing on the PS surface at 25 °C from pH 7 HEPES buffer solutions.

7 Adsorption isotherms for phenylalanine peptides (2, 3, and 4 units) adsorbing on the PS surface at 25 °C from pH 7 HEPES buffer solutions.

8 Adsorption isotherms for glycine peptides (3, 4, and 5 units) adsorbing on the PS surface at 25 °C from pH 7 HEPES buffer solutions.

9 Adsorption isotherms for tyrosine peptides (2, 3, and 6 units) adsorbing on the BzPVP surface at 25 °C from pH 7 HEPES buffer solutions.

…”

“…This contribution describes an experimental procedure for measuring submolecular-level interaction energies involved in the process of peptide adsorption on polymer films; it expands on our preliminary study, which was the topic of a previous communication . The objective of this study was to use SPR to measure the Gibbs free energy change on adsorption (Δ G ad ) for homopeptides on highly uniform, nanothin polymer films and to use these data, along with the principle of additivity, to predict Δ G ad for homologous homopeptides with a larger number of residue units, as well as a mixed-residue peptide, leucine enkephalin.…”

Modelling and Characterization of the Sorption of Kynurenic Acid on Protein Surfaces

“…Chemical or physical adsorption onto the gold surface changes the refractive index of the dielectric, thereby the propagation constant of the surface plasmon is also changed [6]. Still, several research groups have published their results in the topic of characterization of different biomolecule interactions [7][8][9][10], but only a few articles offer deeper information on the temperature-dependent interactions between peptides or proteins and potential drug molecules by using SPR [11,12]. The objective of the present work was to provide complementary data on the interactions between serum albumins and KYNA by using only SPR experiments.…”