Comparisons of the foaming and interfacial properties of whey protein isolate and egg white proteins

Whipped foams (10%, w/v protein, pH 7.0) were prepared from commercially available samples of whey protein isolate (WPI) and egg white protein (EWP), and subsequently compared based on yield stress (τ₀), overrun and drainage stability. Adsorption rates and interfacial rheological measurements at a model air/water interface were quantified via pendant drop tensiometry to better understand foaming differences among the ingredients. The highest τ₀ and resistance to drainage were observed for standard EWP, followed by EWP with added 0.1% (w/w) sodium lauryl sulfate, and then WPI. Addition of 25% (w/w) sucrose increased τ₀ and drainage resistance of the EWP-based ingredients, whereas it decreased τ₀ of WPI foams and minimally affected their drainage rates. These differing sugar effects were reflected in the interfacial rheological measurements, as sucrose addition increased the dilatational elasticity for both EWP-based ingredients, while decreasing this parameter for WPI. Previously observed relationships between τ₀ and interfacial rheology did not hold across the protein types; however, these measurements did effectively differentiate foaming behaviors within EWP-based ingredients and within WPI. Interfacial data was also collected for purified β-lactoglobulin (β-lg) and ovalbumin, the primary proteins of WPI and EWP, respectively. The addition of 25% (w/w) sucrose increased the dilatational elasticity for adsorbed layers of β-lg, while minimally affecting the interfacial rheology of adsorbed ovalbumin, in contrast to the response of WPI and EWP ingredients. These experiments underscore the importance of utilizing the same materials for interfacial measurements as used for foaming experiments, if one is to properly infer interfacial information/mechanisms and relate this information to bulk foaming measurements. The effects of protein concentration and measurement time on interfacial rheology were also considered as they relate to bulk foam properties. This data should be of practical assistance to those designing aerated food products, as it has not been previously reported that sucrose addition improves the foaming characteristics of EWP-based ingredients while negatively affecting the foaming behavior of WPI, as these types of protein isolates are common to the food industry.     

Effect of protein aggregates on foaming properties of β-lactoglobulin

Our paper aims at determining the respective part of protein aggregates and non-aggregated proteins in the foam formation and stability of β-lactoglobulin. We report results on fractal aggregates formed at neutral pH and strong ionic strength (aggregates size from 30 to 190 nm). Pure aggregates and mixtures of non-aggregated/aggregated proteins at varying ratios were used. The capacity of aggregates to form and stabilize foams has been studied in relation with their ability to absorb at air/water interfaces. Our results show that protein aggregates are not able by themselves to improve the foaming properties but participate to a better foam stabilization in the presence of non-aggregated proteins. Non-aggregated proteins appear to be necessary to produce stable foams. We have shown that the amount and the size of aggregates had an influence on the drainage rate.     

Emulsifying and foaming properties of amaranth seed protein isolates

The emulsifying and foaming properties of amaranth seed protein isolates prepared by wet extraction methods, such as isoelectric precipitation and dialysis, were investigated. The various isolates differ from each other in many ways. The isolate prepared by isoelectric precipitation mainly contains the globulin but not the albumin fraction and a considerable amount of polysaccharides, while the other isolate prepared by the dialysis method contains all the globulin and albumin fractions. The protein-polysaccharide complexes enhance emulsion stability due to steric repulsion effects. Measurements of the emulsion stability show that the studied protein isolates act as effective stabilizing agents. Foam expansion is dominated by the surface activity and availability of protein in the solution, while foam stability is determined by the properties of the interfacial layer. The results show that amaranth protein isolates act as an effective foaming agent. Both foaming properties intensified from the presence of protein-polysaccharide complexes.     

Effect of limited hydrolysis on the interfacial rheology and foaming properties of beta-lactoglobulin A

Hydrolysis of beta-lactoglobulin (beta-Lg), genetic variant A, using a serine protease specific for glutamic and aspartic acid residues from Bacillus licheniformis (BLP), resulted in improved foam overrun and foam stability. Limited hydrolysis (19-26% hydrolysed beta-Lg) led to a more rapid increase in the viscoelastic properties of air/water interfacial films and a concomitant increase in foam overrun compared with intact beta-Lg, presumably due to increased exposure of hydrophobic areas. The increased exposure did not, however, cause formation of an interfacial layer with increased viscoelastic properties. More extended hydrolysis (86% hydrolysed beta-Lg) resulted in a higher initial overrun than the unhydrolysed sample and the best foam stability. The interfacial elasticity and viscosity, though, was the lowest observed. Thus, high maximum values of these interfacial properties are not necessary prerequisites for formation of a voluminous and stable foam.     

Presence of protein polymorphism in karasurin, an abortifacient and anti-tumor protein, identified with physicochemical properties.

Karasurin is an abortifacient plant protein isolated from fresh root tubers of Trichosanthes kirilowii Maximowicz var. japonicum Kitamrra (Cucurbitaceae). This study describes the presence of protein polymorphism in karasurin (karasurin-A and karasurin-B) separated by ion-exchange chromatography. Two components showed no differences in the molecular weight (ca. 28000), the amino acid composition, the neutral sugar content and part of the amino acid sequence. A unique difference was observed in their isoelectric points (10.1 for karasurin-A and 10.2 for karasurin-B). However, modifications of glycosylation or phosphorylation were not found. Biological assays for inducing mid-term abortion in pregnant mice and inhibition of the growth of BeWo cells gave no significant differences between them. The presence of protein polymorphism in karasurin, whose biological significance is not yet understood, is a first finding among several abortifacient proteins.     

Exploring the physicochemical and morphological properties of peptide-hybridized dendrimers (DendriPeps) and their aggregates

This article presents an integrated experimental and computational study of DendriPeps, a novel class of dendrimers featuring a polyamidoamine (PAMAM) backbone hybridized with peptide segments. Hydroxyl-terminated Generation 2 (G.2) DendriPeps, comprising either four lysines (Lys) or four glutamic acids (Glu), and G.3 DendriPeps, comprising 8 Lys or 8 Glu, were first characterized in terms of hydrodynamic radius (R_h) and ζ-potential in aqueous solution. Unlike PAMAM dendrimers, DendriPeps form aggregates with R_h between 60 and 980 nm and ζ-potential between −130 and 80 mV despite their strong net charge. Upon application of shear, all aggregates disassemble into monomeric DendriPeps (R_h ~ 1–3 nm), but reform rapidly as shear is removed. Rheological characterization confirmed that DendriPep aggregates are disrupted by mild shear, but reform reversibly. Molecular dynamics simulations, informed by titrimetry, suggest that DendriPep aggregation derives from their multipolar structure and ability to rearrange the intermolecular/intramolecular pairing of titratable moieties at different pH values.     

Deriving the phylogenetic information from some physicochemical properties of protein sequences computed

The evolutionary relationships of organisms are traditionally delineated by the alignment‐based methods using some DNA or protein sequences. In the post‐genome era, the phylogenetics of life could be inferred from many sources such as genomic features, not just from comparison of one or several genes. To investigate the possibility that the physicochemical properties of protein sequences might reflect the phylogenetic ones, an alignment‐free method using a support vector machine (SVM) classifier is implemented to establish the phylogenetic relationships between some protein sequences. There are two types of datasets, namely, the “Enzymatic” (assigned by an EC accession) and “Proteins” used to train the SVM classifiers. By computing the F‐score for feature selection, we find that the classification accuracies of trained SVM classifiers could be significantly enhanced to 84% and 80%, respectively, for the enzymatic and “proteins” datasets classified if the protein sequences are represented with some top 255 features selected. These show that some physicochemical features of amino acid sequences selected are sufficient for inferring the phylogenetic properties of the protein sequences. Moreover, we find that the selected physicochemical features appear to correlate with the physiological characteristic of the taxonomic classes classified. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Synthesis and physicochemical properties of highly soluble tetra-tert-butyl-2,3-naphthalocyanine complexes of lanthanides

Tetra-tert-butyl-2,3-naphthalocyanine complexes of lanthanides were obtained by the reaction of tetra-tert-butyl-2,3-nap hthalocyanine with lanthanide salts. Oxidation and aggregation of these complexes were studied by electronic and ESR spectroscopies.Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 99-102, January, 1996.     

Thorium compounds with non-metals: Electronic structure, chemical bond, and physicochemical properties

The current state of research on the nature of the chemical bond and the physicochemical properties of binary Th-X (X = H, B, C, N, O, P, S, As, Se, Sb) and ternary (carbonitrides, thorates, and silicates) thorium compounds by modern ab initio methods of the band structure theory is reviewed. The possibilities of the ab initio band structure methods in describing the structural states, phase stability, elasticity characteristics, X-ray emission, absorption, and photoelectron spectra of thorium-containing systems are discussed.     

Characterisation and foaming properties of hydrolysates derived from rapeseed isolate

Two hydrolysis methods used to obtain rapeseed isolate derivates were compared: chemical hydrolysis performed under alkaline conditions and pepsic proteolysis performed under acidic conditions. The mean molecular weights obtained for the hydrolysates varied from 26 to 2.5 kDa, depending on the level of hydrolysis. Further characterisation showed that, at the same level of hydrolysis, the chemical hydrolysates differed by their charges and hydrophobicity from those derived from enzymatic digestion. Analysis of the foaming properties showed, for both cases, that a limited degree of hydrolysis, around 3%, was sufficient to optimise the foaming properties of the isolate despite the different physicochemical properties of the peptides generated. The study of foaming properties at basic, neutral and acidic pHs showed that the hydrolysate solutions yielded dense foams which drained slowly and which maintained a very stable volume under the three pH conditions tested.     

N-Substituted-3-aminopropylsilsesquioxanes: synthesis,physicochemical properties,and application

Russian Chemical Bulletin - Synthesis and study of the physicochemical properties of silsesquioxanes modified with 3-aminopropyl, 2-aminoethyl-3-aminopropyl, and dithiooxamide groups was carried...     

Fluorinated self-assembled monolayers: composition,structure and interfacial properties

Over the past several years, various fluorinated self-assembled monolayers (F-SAMs) on gold have been used to study the interfacial properties of fluorocarbon interfaces. This review focuses on the structures of selected F-SAMs and describes how the structures relate to various interfacial properties, such as wettability, friction, X-ray induced damage and ion-surface collisions.     

Amphiphilic micro- and nanogels: Combining properties from internal hydrogel networks,solid particles,and micellar aggregates

Polymeric micro- and nanogels are defined by their water-swollen hydrophilic networks that can often impart outstanding biocompatibility and high-colloidal stability. Unfortunately, this highly hydrophilic nature limits their potential in areas where hydrophobic or amphiphilic interactions are required, for example, the delivery of hydrophobic cargoes or tailored interactions with amphipathic (bio-)surfaces. To overcome this limitation, amphiphilic micro−/nanogels are emerging as new colloidal materials that combine properties from hydrogel networks with hydrophobic segments, known from solid hydrophobic polymer particles or micellar cores. The ability to accurately adjust the balance of hydrophobic and hydrophilic components in such amphiphilic colloidal systems enables new tailored properties. This opens up new applications ranging from the controlled and sustained delivery of hydrophobic drugs, over carriers for catalytic moieties, to their assembly at hydrophilic/hydrophobic interfaces, for example, as advanced stabilizers in Pickering emulsions. While promising, the synthetic realization of such amphiphilic materials remains challenging since hydrophobic and hydrophilic moieties need to be combined in a single colloidal system. As a result, adjusting the micro−/nanogel amphiphilicity often changes the colloidal features too. To overcome these limitations, various strategies have been reported. The aim of this review is to give a brief overview of important synthetic tools, considering both advantages and disadvantages, thus critically evaluating their potential in different research fields.     

Isolation,purification, and some physicochemical properties of glucose isomerase from Streptomyces atratus

A highly purified glucose isomerase with a specific activity 23.5 times greater than that of a homogenate of the mycelium has been obtained fromStreptomyces atratus by methods of homogenization from the freeze-dried biomass, heat treatment (70°C, 10 min), ion-exchange chromatography, and gel filtration. The yield of enzyme on the initial biomass was 51.8%. The molecular mass of the enzyme has been determined by various methods as 160 kDa but in the presence of sodium dodecyl sulfate in thin-layer PAG it amounts to 40 kDa.Institute of Microbiology, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 524–528, July–August, 1990.     

Synthesis, physicochemical and biological properties of oligonucleotides incorporated with amino-isonucleosides

Antisense oligonucleotides(ASONs) and siRNAs have been applied extensively for the regulation of cellular and viral gene expression,and RNAi is currently one of the most promising new approaches for anti-tumor and anti-viral therapy.In order to improve bioactivity properties and physicochemical properties of siRNA,we synthesized a novel class of ASONs II-VII incorporated with amino-isonucleoside(isoA1 and isoA2) for investigation on basic physicochemical properties.Then we designed amino-isonucleoside(isoA1,isoA2 and isoT1) incorporated siRNA 2-7.Some meaningful results have been obtained from the physicochemical property experiments in ASONs.In RNAi potency experiments,we investigated RNAi potency of each strand of the siRNA.These amino-isonucleosides incorporated siRNAs showed promising bioactivity properties and had position specificity.Reduced off target effect from sense strand loading in siRNA application was observed.     

Model colloidal fluid with competing interactions: bulk and interfacial properties

Using a simple mean field density functional theory (DFT), the authors investigate the structure and phase behavior of a model colloidal fluid composed of particles interacting via a pair potential which has a hard core of diameter sigma, is attractive Yukawa at intermediate separations, and is repulsive Yukawa at large separations. The authors analyze the form of the asymptotic decay of the bulk fluid correlation functions, comparing results from DFT with those from the self-consistent Ornstein-Zernike approximation (SCOZA). In both theories the authors find rich crossover behavior, whereby the ultimate decay of correlation functions changes from monotonic to long wavelength damped oscillatory decay on crossing certain lines in the phase diagram or sometimes from oscillatory to oscillatory with a longer wavelength. For some choices of potential parameters the authors find, within the DFT, a lambda line at which the fluid becomes unstable with respect to periodic density fluctuations. SCOZA fails to yield solutions for state points near such a lambda line. The propensity towards clustering of particles, which is reflected by the presence of a long wavelength (>sigma) slowly decaying oscillatory pair correlation function, and a structure factor that exhibits a very sharp maximum at small but nonzero wave numbers, is enhanced in states near the lambda line. The authors present density profiles for the planar liquid-gas interface and for fluids adsorbed at a planar hard wall. The presence of a nearby lambda transition gives rise to pronounced long wavelength oscillations in the one-body density profiles at both types of interface.     

Solution properties, electrochemical behavior and protein interactions of water soluble triosmium carbonyl clusters

The synthesis and solution chemistry of the water soluble clusters [Os₃(CO)₉(μ-η²-Bz)(μ-H)L⁺] (HBz=quinoxaline, L⁺=[P(OCH₂CH₂NMe₃)₃I₃], 1) along with its negatively charged analog [Os₃(CO)₉(μ-η²-Bz)(μ-H)L⁻] (L⁻=[P(C₆H₄SO₃)₃Na₃], 2) are reported. In addition, we have examined the reduction potentials of the complexes [Os₃(CO)₉(μ-η²-Bz)(μ-H)L] (HBz=phenanthridine, L=L⁺ (3); HBz=5,6 benzoquinoline, L=L⁺ (4); HBz=3-amino quinoline, L=L⁺ (5); HBz=3-amino quinoline, L=L⁻ (6). The neutral analog of 1 and 2 [Os₃(CO)₉(μ-η²-Bz)(μ-H) PPh₃] (Bz=quinoxaline, 7) was also examined for comparison. Both compounds 1 and 2 show pH dependent NMR spectra that are interpreted in terms of the extent of protonation of the uncoordinated quinoxaline nitrogen which impacts the degree of aggregation of the clusters in aqueous solution. Compound 1 undergoes a reversible 1e⁻ reduction in water while 2 undergoes a quasi-reversible 1e⁻ reduction at more negative potentials as expected from the difference in charge on the phosphine ligand. Compound 7 undergoes a marginally reversible CV in methylene chloride at a potential intermediate between the positively and negatively charged clusters. The overall stability of the radical anions of 1, 2 and 7 is somewhat less than the corresponding decacarbonyl [Os₃(CO)₁₀(μ-η²-Bz)(μ-H)] (HBz=quinoxaline). While complexes 1 and 2 show reversible 1e⁻ reductions, all the other complexes examined show 1e⁻ and/or two 1e⁻ irreversible reductions in aqueous and non-aqueous solvents. The potentials for these complexes follow expected trends relating to the charge on the phosphine and the pH of the aqueous solutions. The ligand dependent trends are compared with those of the previously reported corresponding decacarbonyls. The interactions of the positively and negatively charged clusters with albumin have been investigated using the transverse and longitudinal relaxation times of the hydride resonances as probes of binding to the protein. Evidence of binding is observed for both the positive and negative clusters but the positive and negative clusters exhibit distinctly different rotational correlation times. Two additional complexes [Os₃(CO)₉(μ-η²-Bz)(μ-H)L] (HBz=2-methylbenzimidazole, L=L⁺ (8); L=L⁻ (10) and HBz=quinoline-4-carboxaldehyde, L=L⁺ (9); L=L⁻ (11)) are reported in connection with these studies.     

Effect of time on the interfacial and foaming properties of beta-lactoglobulin/acacia gum electrostatic complexes and coacervates at pH 4.2

The electrostatic complexation between beta-lactoglobulin and acacia gum was investigated at pH 4.2 and 25 degrees C. The binding isotherm revealed a spontaneous exothermic reaction, leading to a DeltaHobs = -2108 kJ mol(-1) and a saturation protein to polysaccharide weight mixing ratio of 2:1. Soluble electrostatic complexes formed in these conditions were characterized by a hydrodynamic diameter of 119 +/- 0.6 nm and a polydispersity index of 0.097. The effect of time on the interfacial and foaming properties of these soluble complexes was investigated at a concentration of 0.1 wt % at two different times after mixing (4 min, referred as t approximately 0 h and t = 24 h). At t approximately 0 h, the mixture is mainly made of aggregating soluble electrostatic complexes, whereas after 24 h these complexes have already insolubilize to form liquid coacervates. The surface elasticity, viscosity and phase angle obtained at low frequency (0.01 Hz) using oscillating bubble tensiometry revealed higher fluidity and less rigidity in the film formed at t approximately 0 h. This observation was confirmed by diminishing bubble experiments coupled with microscopy of the thin film. It was thicker, more homogeneous and contained more water at t approximately 0 h as compared to t = 24 h (thinner film, less water). This led to very different gas permeability's of Kt approximately 0 h = 0.021 cm s(-1) and Kt=24 h) = 0.449 cm s(-1), respectively. Aqueous foams produced with the beta-lactoglobulin/acacia gum electrostatic complexes or coacervates exhibited very different stability. The former (t approximately 0 h) had a stable volume, combining low drainage rate and mainly air bubble disproportionation as the destabilization mechanism. By contrast, using coacervates aged for 24 h, the foam was significantly less stable, combining fast liquid drainage and air bubble destabilization though fast gas diffusion followed by film rupture and bubble coalescence. The strong effect of time on the air/water interfacial properties of the beta-lactoglobulin/acacia gum electrostatic complexes can be understood by their reorganization at the interface to form a coacervate phase that is more fluid/viscous at t approximately 0 h vs rigid/elastic at t = 24 h.     

Pickering-stabilized emulsion gels fabricated from wheat protein nanoparticles: Effect of pH,NaCl and oil content

A novel Pickering-stabilized emulsion gel with controlled rheological properties was derived from wheat gliadin nanoparticles-stabilized emulsions by altering preparation conditions (pH, ionic strength or oil content). The formed nanoparticles were relatively small uniform spheres particles (d?相似文献