The limiting thickness of protein films

Mussellwhite, P. R.; Kitchener, J. A.

doi:10.1016/0021-9797(67)90280-9

Cited by 32 publications

(11 citation statements)

References 9 publications

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“…57 In contrast, the interactions can be hydrophobically driven for proteins at such small thicknesses, and the presence of monolayers or multilayers of proteins with very little or no solvent has been observed previously. 58 The coalescence time of a bubble at the air−solution interface corresponded to the viscoelasticity and stability of that interfacial mAb film and provided additional insight into the aggregation propensity of the mAbs in that film. The coalescence times for mAbs 1 and 2 at different film ages are represented in Figure 4.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The presence of a black film in a surfactant solution is usually attributed to the effect of the electrostatic component of the disjoining pressure of the adsorbed film . In contrast, the interactions can be hydrophobically driven for proteins at such small thicknesses, and the presence of monolayers or multilayers of proteins with very little or no solvent has been observed previously …”

Section: Resultsmentioning

confidence: 99%

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Monoclonal Antibody Interfaces: Dilatation Mechanics and Bubble Coalescence

et al. 2018

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Monoclonal antibodies (mAbs) are proteins that uniquely identify targets within the body, making them well-suited for therapeutic applications. However, these amphiphilic molecules readily adsorb onto air-solution interfaces where they tend to aggregate. We investigated two mAbs with different propensities to aggregate at air-solution interfaces. The understanding of the interfacial rheological behavior of the two mAbs is crucial in determining their aggregation tendency. In this work, we performed interfacial stress relaxation studies under compressive step strain using a custom-built dilatational rheometer. The dilatational relaxation modulus was determined for these viscoelastic interfaces. The initial value and the equilibrated value of relaxation modulus were larger in magnitude for the mAb with a higher tendency to aggregate in response to interfacial stress. We also performed single-bubble coalescence experiments using a custom-built dynamic fluid-film interferometer (DFI). The bubble coalescence times also correlated to the mAbs aggregation propensity and interfacial viscoelasticity. To study the influence of surfactants in mAb formulations, polyethylene glycol (PEG) was chosen as a model surfactant. In the mixed mAb/PEG system, we observed that the higher aggregating mAb coadsorbed with PEG and formed domains at the interface. In contrast, for the other mAb, PEG entirely covered the interface at the concentrations studied. We studied the mobility of the interfaces, which was manifested by the presence or the lack of Marangoni stresses. These dynamics were strongly correlated with the interfacial viscoelasticity of the mAbs. The influence of competitive destabilization in affecting the bubble coalescence times for the mixed mAb/PEG systems was also studied.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Monoclonal Antibody Interfaces: Dilatation Mechanics and Bubble Coalescence

et al. 2018

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“…A spread film can be formed at the air/water interface of BSA solutions, even for solutions with an initial bulk concentration as low as 0.5 ppm. − The tendency of BSA to form films is driven by the hydrophobic force, which originates from the uneven distribution of the functional groups on the outer surface of BSA, with consequence that some parts of the surface are less hydrophilic than others. Studies on the adsorbed films of BSA at the air/water interface were conducted decades ago, aiming to reveal the kinetics and structural information. − It is generally accepted that the adsorption kinetics follow two steps: diffusion to the surface and conformational rearrangement within the interface. Evidence from dynamic surface properties shows that the different (E, F, N, B, etc.)…”

Section: Introductionmentioning

confidence: 99%

Salting Up and Salting Down of Bovine Serum Albumin Layers at the Air–Water Interface

2020

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The surface adsorption of bovine serum albumin in pure water and salted aqueous solutions was studied by neutron reflection. With the contrast match technique, the surface excess in null reflecting water as a function of the protein concentration was revealed. It is found that, in a concentration range from 1 ppm (parts per million, mg/L) to 1000 ppm, without salts, the surface excess shows a profound peak at around 20 ppm; with salts, the surface excess increases steadily with the protein concentration. When the surface excess at a specific protein concentration is viewed, the introduction of sodium chloride causes either a salting down effect (surface adsorption decline) or a salting up effect (surface adsorption increase), depending upon the protein concentration. The salting up effect is observed at the low (∼1 ppm) and high (∼1000 ppm) concentrations, and the salting down effect dominates the intermediate concentration range. The change in solution pH relative to the isoelectric point (PI) can act as a simple indicator for the salting up or salting down behavior. When the solution pH is shifted toward the PI by adding salts, surface adsorption enhances; when the solution pH is shifted away from the PI by adding salts, surface adsorption declines.

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“…Here we employ a thin-film balance (TFB) that is particularly suited for investigation of fluid/fluid interfaces. , With the TFB, the interaction force is described by a disjoining pressure Π, (force per film area) as a function of film thickness h . With few exceptions, , previous studies of protein-stabilized foam and emulsion films have been qualitative and have been limited to the analysis of drainage behavior, film lifetimes, or film thicknesses, without reported values of the corresponding disjoining pressure. − It is, therefore, difficult to draw conclusions on the nature of possible thin-film stabilizing forces for aqueous protein solutions. Proteins exhibit a folded conformation in solution (tertiary structure) that is marginally stable, and thus their impetus to adsorb at interfaces and to alter conformation can be large .…”

Section: Introductionmentioning

confidence: 99%

Surface Forces and Drainage Kinetics of Protein-Stabilized Aqueous Films

et al. 2003

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Surface or disjoining forces between protein layers adsorbed at the air/water interface were measured in single, isolated films. Two proteins, β-casein and bovine serum albumin (BSA), were investigated under varying conditions of pH, ionic strength, and degree of aging at the interface. Force−distance curves were determined with a modified thin-film balance and interferometer, using both equilibrium and dynamic methods. Dynamic surface tension and ellipsometry data for β-casein and BSA adsorption at the air/water interface are also reported. Charged β-casein and BSA molecules do not strongly adsorb at the air/water interface. Accordingly, stable films were observed when electrostatic interactions were screened or the proteins were near their isoelectric points. For β-casein, the force−distance curves indicated a transition from an outer to an inner branch at a distance equivalent to the diameter of β-casein. This depended on the interfacial structuring of adsorbed β-casein multilayers at the air/water interface. Upon thinning of the film, BSA retained its native dimensions, whereas β-casein did not. As a consequence, fresh β-casein films are more stable against rupturing than are BSA films. Aging imparted mechanical rigidity to the interfaces, causing nonuniform film drainage and nonequilibrium, trapped dimples. For films of intermediate degree of aging, black-film formation was observed through the formation of noncircular thin spots. Prolonged aging resulted in the development of interfacial aggregated networks and in films of variable thickness that did not respond to changes in capillary pressure.

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The limiting thickness of protein films

Cited by 32 publications

References 9 publications

Monoclonal Antibody Interfaces: Dilatation Mechanics and Bubble Coalescence

Monoclonal Antibody Interfaces: Dilatation Mechanics and Bubble Coalescence

Salting Up and Salting Down of Bovine Serum Albumin Layers at the Air–Water Interface

Surface Forces and Drainage Kinetics of Protein-Stabilized Aqueous Films

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