Charge-Controlled Surface Properties of Native and Fluorophore-Labeled Bovine Serum Albumin at the Air–Water Interface

Richert, Manuela; Rey, Natalia García; Braunschweig, Björn

doi:10.1021/acs.jpcb.8b06481

Cited by 18 publications

(10 citation statements)

References 55 publications

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“…This effect is in fact similar to pH induced changes in SFG spectra when the interfacial isoelectric point is crossed. 16,57 As a result, constructive interference between the contributions from O-H and C-H stretching vibrations is observed when the Nd 3+ and Y 3+ ion concentration is high (peak-like feature at 3060 cm -1 , Figure 2), but is changed to destructive interference when the ion concentration is low (dip-like feature).…”

Section: Interfacial Behavior Of Blg As a Function Of Nd 3+ And Y 3+ ...mentioning

confidence: 99%

Specific Ion Effects of Trivalent Cations on the Structure and Charging State of β-Lactoglobulin Adsorption Layers

2019

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Properties of proteins at interfaces are important to a many processes as well as in soft matter materials such as aqueous foam. Particularly, the protein interfacial behavior is strongly linked to different factors like the solution pH or the presence of electrolytes. Here the nature of the electrolyte ions can significantly modify the interfacial properties of proteins. Therefore, molecular level studies on interfacial structures and charging states are needed. In this work, we addressed the effects of Y 3+ and Nd 3+ cations on the adsorption of the whey protein β-lactoglobulin (BLG) at airwater interfaces as a function of electrolyte concentration. Both cations caused very similar but dramatic changes at the interface and in the bulk solution. Here, measurements of the electrophoretic mobility and vibrational sum-frequency generation spectroscopy (SFG) were applied and consistently showed a reversal of the BLG net charge at remarkably low ion concentrations of 30

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Section: Interfacial Behavior Of Blg As a Function Of Nd 3+ And Y 3+ ...mentioning

confidence: 99%

Specific Ion Effects of Trivalent Cations on the Structure and Charging State of β-Lactoglobulin Adsorption Layers

2019

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“…In this respect, multi-scale approaches have been used, where macroscopic foaming properties are compared with the microscopic (nanoscopic) properties of lamellae (foam films) and interfaces [18][19][20][21][22][23][24][25][26][27] as foam's building blocks. Regarding interfaces, on the focus are the traditional adsorption dynamics studies, as well as rheological [9][10][11][12][13][14], electrical [27,29,35,[47][48][49][50][51], and structural [30,50,51] interfacial characteristics-it is emphasized the crucial role of the rate of adsorption, surface viscoelasticity (surface elasticity is the resistance force to mechanical disturbances), interface charging state and interfacial molecular organization, respectively, to foamability, foam stability and foam rheology. Pronounced viscoelastic characteristics of interfaces have been recognized to enhance foaming properties [10,11,14,28,31].…”

Section: Introductionmentioning

confidence: 99%

β-Lactoglobulin Adsorption Layers at the Water/Air Surface: 4. Impact on the Stability of Foam Films and Foams

et al. 2020

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The complexity and high sensitivity of proteins to environmental factors give rise to a multitude of variables, which affect the stabilization mechanisms in protein foams. Interfacial and foaming properties of proteins have been widely studied, but the reported unique effect of pH, which can be of great interest to applications, has been investigated to a lesser extent. In this paper, we focus on the impact of pH on the stability of black foam films and corresponding foams obtained from solutions of a model globular protein—the whey β-lactoglobulin (BLG). Foam stability was analyzed utilizing three characteristic parameters (deviation time, transition time and half-lifetime) for monitoring the foam decay, while foam film stability was measured in terms of the critical disjoining pressure of film rupture. We attempt to explain correlations between the macroscopic properties of a foam system and those of its major building blocks (foam films and interfaces), and thus, to identify structure-property relationships in foam. Good correlations were found between the stabilities of black foam films and foams, while relations to the properties of adsorption layers appeared to be intricate. That is because pH-dependent interfacial properties of proteins usually exhibit an extremum around the isoelectric point (pI), but the stability of BLG foam films increases with increasing pH (3–7), which is well reflected in the foam stability. We discuss the possible reasons behind these intriguingly different behaviors on the basis of pH-induced changes in the molecular properties of BLG, which seem to be determining the mechanism of film rupture at the critical disjoining pressure.

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“…SFG experiments were performed with a setup that is described elsewhere. , Spectra were taken with the sum frequency, the visible, and the IR beams having s-, s-, and p-polarization (ssp), respectively. The SFG spectra were recorded by tuning the center wavelength of the IR beam in four steps and were normalized to the nonresonant signal of an air-plasma cleaned polycrystalline Au surface.…”

Section: Experimental Detailsmentioning

confidence: 99%

Spiropyran Sulfonates for Photo- and pH-Responsive Air–Water Interfaces and Aqueous Foam

et al. 2020

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Responsive foams and interfaces, are interesting building blocks for active materials that respond and adapt to external stimuli. We have used the photochromic reaction of a spiropyran sulfonate surfactant to render interfacial, rising bubble as well as foaming properties active to light stimuli.In order to address the air-water interface on a molecular level, we have applied sum-frequency generation (SFG) spectroscopy which has provided qualitative information on the surface excess and the interfacial charging state as a function of light irradiation and solution pH. Under blue light irradiation, the surfactant forms a closed ring spiro form (SP), whereas under dark conditions the ring opens and the merocyanine (MC) form is generated. Using SFG spectroscopy, we show that at the interface, different pH conditions of the bulk solution lead to changes in the interfacial charging state. We have exploited the fact that the MC surfactant's O-H group can be deprotonated as a function of pH, and used that to tune the molecules net charge at the interface. In fact, SFG spectroscopy shows that with increasing pH the intensity of the O-H stretching band from interfacial water molecules increases which we associate to an increase in surface net charge. At a pH of 5.3, irradiation with blue light leads to a reversible decrease of O-H intensities, whereas the C-H intensities were unchanged compared to the corresponding intensities under dark conditions. These results are indicative of changes in the surface net charge with light irradiation, which are also expected to influence the foam stability via changes in the electrostatic disjoining pressure. In fact, measurements of the foam stabilities are consistent with this hypothesis with higher foam stability under dark conditions. At pH 2.7 this behavior is reversed as far as the surface tension and surface charging as well as the foam stability are concerned. This is corroborated by rising bubble experiments, which demonstrated an unprecedented reduction of ~30 % in bubble velocity when the bubbles were irradiated with blue light compared to the velocity of bubbles with the

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Charge-Controlled Surface Properties of Native and Fluorophore-Labeled Bovine Serum Albumin at the Air–Water Interface

Cited by 18 publications

References 55 publications

Specific Ion Effects of Trivalent Cations on the Structure and Charging State of β-Lactoglobulin Adsorption Layers

Specific Ion Effects of Trivalent Cations on the Structure and Charging State of β-Lactoglobulin Adsorption Layers

β-Lactoglobulin Adsorption Layers at the Water/Air Surface: 4. Impact on the Stability of Foam Films and Foams

Spiropyran Sulfonates for Photo- and pH-Responsive Air–Water Interfaces and Aqueous Foam

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