Structure and dynamics of egg white ovalbumin adsorbed at the air/water interface

Abstract

The molecular properties of egg white ovalbumin adsorbed at the air/water interface were studied using infrared reflection absorption spectroscopy (IRRAS) and time-resolved fluorescence anisotropy (TRFA) techniques. Ovalbumin adsorbed at the air/water interface adopts a characteristic partially unfolded conformation in which the content of the beta-sheet is 10% lower compared to that of the protein in bulk solution. Adsorption to the interface leads to considerable changes in the rotational dynamics of ovalbumin. The results indicate that the end-over-end mobility of the ellipsoidal protein becomes substantially restricted. This is likely to reflect a preferential orientation of the protein at the interface. Continuous compression of surface layers of ovalbumin causes local aggregation of the protein, resulting in protein-network formation at the interface. The altered protein-protein interactions contribute to the strong increase in surface pressure observed.

Physical and biophysical effects of polysorbate 20 and 80 on darbepoetin alfa

“…Equilibrium for possible polysorbatedarbepoetin alfa interactions are shown in Eqs. (2) and (3), where PS f is the molecular polysorbate, PS m is the polysorbate micelle, NESP f is the darbepoetin alfa monomer, NESP-PS n is the darbepoetin alfa-polysorbate molecules complex, NESP-PS m is the darbepoetin alfa-polysorbate micelle complex, and n is the number of free polysorbate bound to darbepoetin alfa.…”

“…Proteins at the interface can unfold further, exposing more hydrophobic surface in order to enhance amphiphilicity. [1][2][3][4] Interface-solution partitioning and interfacial induced unfolding are not completely reversible, resulting in protein surface loss, misfolding, and aggregation. Surface-active agents, or surfactants, are often added to protein solutions to prevent physical damage or loss as mentioned.…”

The adsorption and unfolding kinetics determines the folding state of proteins at the air–water interface and thereby the equation of state

“…With this method, the spectrum of an infrared (IR) beam is analyzed after specular reflection at the interface. The sensitivity of the amide I region to changes in the secondary structure can be used to gain insight in the protein conformation at a secondary folding level [30][31][32][33][34][35]. More recently also external reflection circular dichroism has been used to assess this information [33].…”

“…More recently also external reflection circular dichroism has been used to assess this information [33]. From a combination of these techniques, several authors conclude that only limited changes in the conformation of proteins occurs upon adsorption at the air-water interface [28,32,34,[36][37][38][39][40]. Maximum changes of up to 10% are observed in the secondary structure, but the globular folding state of the protein is generally found to remain intact [34].…”

Application Potential of Food Protein Modification

“…This effect is further amplified by the finding that local protein concentrations at the air-water interface can reach up to 150 to 300 mg/ml (Meinders et al, 2001). The rate of absorption to the air-water interface has been reported to depend largely on the hydrophobic nature of the protein under investigation (Kudryashova et al, 2003;Wierenga et al, 2003). Increasing the exposed hydrophobicity of proteins by means of conjugation with lipid chains was shown to increase the adsorption rate to the air-water interface .…”