Peptide interfacial adsorption is kinetically limited by the thermodynamic stability of self association.

We present a study of the adsorption of two peptides at the octane-water interface. The first peptide, Lac21, exists in mixed monomer-tetramer equilibrium in bulk solution with an appreciable monomer concentration. The second peptide, Lac28, exists as a tetramer in solution, with minimal exposed hydrophobic surface. A kinetic limitation to interfacial adsorption exists for Lac28 at moderate to high surface coverage that is not observed for Lac21. We estimate the potential energy barrier for Lac28 adsorption to be 42 kJ/mol and show that this is comparable to the expected free energy barrier for tetramer dissociation. This finding suggests that, at moderate to high surface coverage, adsorption is kinetically limited by the availability of interfacially active monomeric "domains" in the subinterfacial region. We also show how the commonly used empirical equation for protein adsorption dynamics can be used to estimate the potential energy barrier for adsorption. Such an approach is shown to be consistent with a formal description of diffusion-adsorption, provided a large potential energy barrier exists. This work demonstrates that the dynamics of interfacial adsorption depend on protein thermodynamic stability, and hence structure, in a quantifiable way.

[1]  E. Blomberg,et al.  Protein interactions at solid surfaces , 1995 .

[2]  A. Fersht.  Structure and mechanism in protein science , 1998 .

[3]  E. Dickinson,et al.  Theoretical and experimental investigations of adsorbed protein structure at a fluid interface. , 1996 .

[4]  W. Norde,et al.  The adsorption-induced secondary structure of beta-casein and of distinct parts of its sequence in relation to foam and emulsion properties. , 1999, Biochimica et biophysica acta.

[5]  L. Mueller,et al.  Characterization of a new four‐chain coiled‐coil: Influence of chain length on stability , 1995, Protein science : a publication of the Protein Society.

[6]  E. Dickinson,et al.  Neutron reflectivity of adsorbed β-casein and β-lactoglobulin at the air/water interface , 1995 .

[7]  L. Tordai,et al.  Time‐Dependence of Boundary Tensions of Solutions I. The Role of Diffusion in Time‐Effects , 1946 .

[8]  H. Vogel,et al.  Formation of stable polypeptide monolayers at interfaces: controlling molecular conformation and orientation. , 1997, Biophysical journal.

[9]  Reinhard Miller,et al.  Determination of equilibrium surface tension values by extrapolation via long time approximations , 1997 .

[10]  M. Phillips,et al.  Proteins at liquid interfaces: II. Adsorption isotherms , 1979 .

[11]  A. Zamyatnin,et al.  Protein volume in solution. , 1972, Progress in biophysics and molecular biology.

[12]  M. T. Tyn,et al.  Prediction of diffusion coefficients of proteins , 1990, Biotechnology and bioengineering.

[13]  E. Dickinson,et al.  Time—dependent surface viscosity of adsorbed films of casein + gelatin at the oil—water interface , 1985 .

[14]  A. Adamson.  Physical chemistry of surfaces , 1960 .

[15]  M. Phillips,et al.  Proteins at liquid interfaces: I. Kinetics of adsorption and surface denaturation , 1979 .

[16]  L. Liggieri,et al.  Sorption kinetics considered as a renormalized diffusion process , 1993 .