Influence of the porphyrin structure and linker length on the interfacial behavior of phospholipid-porphyrin conjugates

Protein–polyphenol interactions influence emulsifying properties in both directions. Puerarin (PUE) is an isoflavone that can promote the formation of heat-set gels with whey protein isolate (WPI) through hydrogen bonding. We examined whether PUE improves the emulsifying properties of WPI and the stabilities of the emulsions. We found that forming composites with PUE improves the emulsifying properties of WPI in a concentration-dependent manner. The optimal concentration is 0.5%, which is the highest PUE concentration that can be solubilized in water. The PUE not only decreased the droplet size of the emulsions, but also increased the surface charge by forming composites with the WPI. A 21 day storage test also showed that the maximum PUE concentration improved the emulsion stability the most. A PUE concentration of 0.5% improved the stability of the WPI emulsions against environmental stress, especially thermal treatment. Surface protein loads indicated more protein was adsorbed to the oil droplets, resulting in less interfacial WPI concentration due to an increase in specific surface areas. The use of PUE also decreased the interfacial tension of WPI at the oil–water interface. To conclude, PUE improves the emulsifying activity, storage, and environmental stability of WPI emulsions. This result might be related to the decreased interfacial tension of WPI–PUE composites.

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β-Lactoglobulin Adsorption Layers at the Water/Air Surface: 5. Adsorption Isotherm and Equation of State Revisited, Impact of pH

Colloids and Interfaces ◽

10.3390/colloids5010014 ◽

2021 ◽

Vol 5 (1) ◽

pp. 14

Author(s):

Georgi G. Gochev ◽

Volodymyr I. Kovalchuk ◽

Eugene V. Aksenenko ◽

Valentin B. Fainerman ◽

Reinhard Miller

Keyword(s):

Theoretical Description ◽

Fluid Interfaces ◽

Interfacial Behavior ◽

Current State ◽

Air Interface ◽

Direct Measurements ◽

Wide Range ◽

Dilational Viscoelasticity ◽

Parameter Values ◽

Β Lactoglobulin

The theoretical description of the adsorption of proteins at liquid/fluid interfaces suffers from the inapplicability of classical formalisms, which soundly calls for the development of more complicated adsorption models. A Frumkin-type thermodynamic 2-d solution model that accounts for nonidealities of interface enthalpy and entropy was proposed about two decades ago and has been continuously developed in the course of comparisons with experimental data. In a previous paper we investigated the adsorption of the globular protein β-lactoglobulin at the water/air interface and used such a model to analyze the experimental isotherms of the surface pressure, Π(c), and the frequency-, f-, dependent surface dilational viscoelasticity modulus, E(c)f, in a wide range of protein concentrations, c, and at pH 7. However, the best fit between theory and experiment proposed in that paper appeared incompatible with new data on the surface excess, Γ, obtained from direct measurements with neutron reflectometry. Therefore, in this work, the same model is simultaneously applied to a larger set of experimental dependences, e.g., Π(c), Γ(c), E(Π)f, etc., with E-values measured strictly in the linear viscoelasticity regime. Despite this ambitious complication, a best global fit was elaborated using a single set of parameter values, which well describes all experimental dependencies, thus corroborating the validity of the chosen thermodynamic model. Furthermore, we applied the model in the same manner to experimental results obtained at pH 3 and pH 5 in order to explain the well-pronounced effect of pH on the interfacial behavior of β-lactoglobulin. The results revealed that the propensity of β-lactoglobulin globules to unfold upon adsorption and stretch at the interface decreases in the order pH 3 > pH 7 > pH 5, i.e., with decreasing protein net charge. Finally, we discuss advantages and limitations in the current state of the model.

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Upper digestion fate of citrus pectin-stabilized emulsion: An interfacial behavior perspective

Carbohydrate Polymers ◽

10.1016/j.carbpol.2021.118040 ◽

2021 ◽

Vol 264 ◽

pp. 118040

Author(s):

Rujun Wei ◽

Shaojie Zhao ◽

Lin Zhang ◽

Liping Feng ◽

Chengying Zhao ◽

...

Keyword(s):

Interfacial Behavior ◽

Citrus Pectin

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Reconstructing the Free Energy Profiles Describing the Switching Mechanism of a pH-Dependent DNA Nanodevice from ABMD Simulations

Applied Sciences ◽

10.3390/app11094052 ◽

2021 ◽

Vol 11 (9) ◽

pp. 4052

Author(s):

Alice Romeo ◽

Mattia Falconi ◽

Alessandro Desideri ◽

Federico Iacovelli

Keyword(s):

Free Energy ◽

Double Helix ◽

Minimum Energy ◽

Switching Mechanism ◽

Linker Length ◽

Energy Profiles ◽

Functional Dna ◽

Triplex Forming Oligonucleotide ◽

Dynamics Simulations ◽

Free Energy Profiles

The pH-responsive behavior of six triple-helix DNA nanoswitches, differing in the number of protonation centers (two or four) and in the length of the linker (5, 15 or 25 bases), connecting the double-helical region to the single-strand triplex-forming region, was characterized at the atomistic level through Adaptively Biased Molecular Dynamics simulations. The reconstruction of the free energy profiles of triplex-forming oligonucleotide unbinding from the double helix identified a different minimum energy path for the three diprotic nanoswitches, depending on the length of the connecting linker and leading to a different per-base unbinding profile. The same analyses carried out on the tetraprotic switches indicated that, in the presence of four protonation centers, the unbinding process occurs independently of the linker length. The simulation data provide an atomistic explanation for previously published experimental results showing, only in the diprotic switch, a two unit increase in the pKa switching mechanism decreasing the linker length from 25 to 5 bases, endorsing the validity of computational methods for the design and refinement of functional DNA nanodevices.

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