scholarly journals Improved Gel Properties of Whey Protein-Stabilized Emulsions by Ultrasound and Enzymatic Cross-Linking

Gels ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 135
Author(s):  
Yanli Zhao ◽  
Shiqi Xue ◽  
Xinyue Zhang ◽  
Tiehua Zhang ◽  
Xue Shen
Keyword(s):  
Whey Protein ◽  
Disulfide Bonds ◽  
Noncovalent Interactions ◽  
Textural Properties ◽  
Industrial Applications ◽  
Cross Linking ◽  
Similar Frequency ◽  
Soluble Aggregate ◽  
Gelation Behavior ◽  
Cross Links

This study investigated the effects of high-intensity ultrasound (HUS) and transglutaminase pretreatment on the gelation behavior of whey protein soluble aggregate (WPISA) emulsions. HUS pretreatment and TGase-mediated cross-linking delayed the onset of gelation but significantly increased (p < 0.05) the gel firmness (G′) both after gel formation at 25 °C and during storage at 4 °C. The frequency sweep test indicated that all gels had a similar frequency dependence at 4 and 25 °C, and the elasticity and viscosity of the WPISA-stabilized emulsion gel were significantly enhanced by HUS pretreatment and TGase-mediated cross-linking (p < 0.05). HUS and TGase-mediated cross-linking greatly improved the textural properties of WPISA-stabilized emulsion gels, as revealed by their increases in gel hardness, cohesiveness, resilience, and chewiness. HUS pretreatment and TGase-mediated cross-linking significantly increased the water-holding capacity but decreased the swelling ratios of the gels (p < 0.05). Interactive force analysis confirmed that noncovalent interactions, disulfide bonds, and TGase-induced covalent cross-links were all involved in the formation of gel networks. In conclusion, the combination of HUS and TGase-mediated cross-linking were beneficial for improving the gelation properties of WPISA-stabilized emulsion as a controlled release vehicle for potential food industrial applications.

scholarly journals Mechanical and Barrier Properties of Potato Protein Isolate-Based Films

Coatings ◽  
2018 ◽  
Vol 8 (2) ◽  
pp. 58 ◽  
Author(s):  
David Schäfer ◽  
Matthias Reinelt ◽  
Andreas Stäbler ◽  
Markus Schmid
Keyword(s):  
Whey Protein ◽  
Functional Properties ◽  
Barrier Properties ◽  
Whey Protein Isolate ◽  
Protein Isolate ◽  
Cross Linking ◽  
Potato Protein ◽  
Water Sorption Isotherm ◽  
Barrier Performance ◽  
Cross Links

Potato protein isolate (PPI) was studied as a source for bio-based polymer films. The objective of this study was the determination of the packaging-relevant properties, including the mechanical properties and barrier performance, of casted potato protein films. Furthermore, the films were analyzed for cross-linking properties depending on the plasticizer concentration, and compared with whey protein isolate (WPI)-based films. Swelling tests and water sorption isotherm measurements were performed to determine the degree of swelling, the degree of cross-linking, and the cross-linking density using the Flory–Rehner approach. The effects of different plasticizer types and contents on compatibility with potato protein were studied. Glycerol was the most compatible plasticizer, as it was the only plasticizer providing flexible standalone films in the investigated concentration range after three weeks of storage. Results indicated that increasing glycerol content led to decreasing cross-linking, which correlated in an inversely proportional manner to the swelling behavior. A correlation between cross-linking and functional properties was also reflected in mechanical and barrier characterization. An increasing number of cross-links resulted in higher tensile strength and Young’s modulus, whereas elongation was unexpectedly not affected. Similarly, barrier performance was significantly improved with increasing cross-linking. The overall superior functional properties of whey protein-based films were mainly ascribed to their higher percentage of cross-links. This was primarily attributed to a lower total cysteine content of PPI (1.6 g/16 g·N) compared to WPI (2.8 g/16 g·N), and the significant lower solubility of potato protein isolate in water at pH 7.0 (48.1%), which was half that of whey protein isolate (96%). Comparing on an identical glycerol level (66.7% (w/w protein)), the performance of potato protein isolate was about 80% that of whey protein isolate regarding cross-linking, as well as mechanical and barrier properties.

scholarly journals Impact of Hydrolyzed Whey Protein on the Molecular Interactions and Cross-Linking Density in Whey Protein Isolate-Based Films

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Markus Schmid ◽  
Sandra Pröls ◽  
Daniel M. Kainz ◽  
Felicia Hammann ◽  
Andreas Stäbler
Keyword(s):  
Whey Protein ◽  
Molecular Interactions ◽  
Noncovalent Interactions ◽  
Barrier Properties ◽  
Protein Isolate ◽  
Cross Linking ◽  
Disulphide Bonds ◽  
Swelling Studies ◽  
Solubility Studies ◽  
The Cross

The effect of the amount of hydrolyzed WPI (h-WPI) in WPI-based films on the technofunctional properties and structure of the films has not hitherto been systematically researched. The main objective of this study was therefore to explore the quantitative and qualitative molecular interactions and structures of these films. Different buffer systems were used for the solubility studies to obtain information about the qualitative molecular interactions. Swelling studies were performed to provide qualitative statements about the WPI network. In addition, the cross-linking density (CLD) of the WPI-based films was derived from the swelling tests. The measurements showed that increasing the h-WPI content decreases the CLD significantly. The CLD values of films with 0% and 50% h-WPI content were1.61·10-4 mol·cm−3and0.25·10-4 mol·cm−3. The study indicates that noncovalent interactions have more influence on barrier properties than the cross-linking density through disulphide bonds. In general, the results of the swelling tests correlated with the solubility studies.

scholarly journals Chemistry of collagen cross-links: glucose-mediated covalent cross-linking of type-IV collagen in lens capsules

1993 ◽  
Vol 296 (2) ◽  
pp. 489-496 ◽  
Author(s):  
A J Bailey ◽  
T J Sims ◽  
N C Avery ◽  
C A Miles
Keyword(s):  
Type Iv Collagen ◽  
Cross Linking ◽  
Mechanical And Thermal Properties ◽  
Maximum Strain ◽  
Scanning Calorimetry ◽  
Melting Temperatures ◽  
Type Iv ◽  
Collagen Molecules ◽  
Cross Links

The incubation of lens capsules with glucose in vitro resulted in changes in the mechanical and thermal properties of type-IV collagen consistent with increased cross-linking. Differential scanning calorimetry (d.s.c.) of fresh lens capsules showed two major peaks at melting temperatures Tm 1 and Tm 2 at approx. 54 degrees C and 90 degrees C, which can be attributed to the denaturation of the triple helix and 7S domains respectively. Glycosylation of lens capsules in vitro for 24 weeks caused an increase in Tm 1 from 54 degrees C to 61 degrees C, while non-glycosylated, control incubated capsules increased to a Tm 1 of 57 degrees C. The higher temperature required to denature the type-IV collagen after incubation in vitro suggested increased intermolecular cross-linking. Glycosylated lens capsules were more brittle than fresh samples, breaking at a maximum strain of 36.8 +/- 1.8% compared with 75.6 +/- 6.3% for the fresh samples. The stress at maximum strain (or ‘strength’) was dramatically reduced from 12.0 to 4.7 N.mm.mg-1 after glycosylation in vitro. The increased constraints within the system leading to loss of strength and increased brittleness suggested not only the presence of more cross-links but a difference in the location of these cross-links compared with the natural lysyl-aldehyde-derived cross-links. The chemical nature of the fluorescent glucose-derived cross-link following glycosylation was determined as pentosidine, at a concentration of 1 pentosidine molecule per 600 collagen molecules after 24 weeks incubation. Pentosidine was also determined in the lens capsules obtained from uncontrolled diabetics at a level of about 1 per 100 collagen molecules. The concentration of these pentosidine cross-links is far too small to account for the observed changes in the thermal and mechanical properties following incubation in vitro, clearly indicating that another as yet undefined, but apparently more important cross-linking mechanism mediated by glucose is taking place.

scholarly journals Cross-linking of the electron-transfer flavoprotein to electron-transfer flavoprotein-ubiquinone oxidoreductase with heterobifunctional reagents

1988 ◽  
Vol 255 (3) ◽  
pp. 869-876 ◽  
Author(s):  
D J Steenkamp
Keyword(s):  
Electron Transfer ◽  
Small Subunit ◽  
Cross Linking ◽  
Minor Effect ◽  
Electron Transfer Flavoprotein ◽  
Ubiquinone Oxidoreductase ◽  
Lysine Residues ◽  
Cross Links ◽  
A Minor ◽  
Chemical Cross Linking

The mitochondrial electron-transfer flavoprotein (ETF) is a heterodimer containing only one FAD. In previous work on the structure-function relationships of ETF, its interaction with the general acyl-CoA dehydrogenase (GAD) was studied by chemical cross-linking with heterobifunctional reagents [D. J. Steenkamp (1987) Biochem. J. 243, 519-524]. GAD whose lysine residues were substituted with 3-(2-pyridyldithio)propionyl groups was preferentially cross-linked to the small subunit of ETF, the lysine residues of which had been substituted with 4-mercaptobutyramidine (MBA) groups. This work was extended to the interaction of ETF with ETF-ubiquinone oxidoreductase (ETF-Q ox). ETF-Q ox was partially inactivated by modification with N-succinimidyl 3-(2-pyridyldithio)propionate to introduce pyridyl disulphide structures. A similar modification of ETF caused a large increase in the apparent Michaelis constant of ETF-Q ox for modified ETF owing to the loss of positive charge on some critical lysines of ETF. When ETF-Q ox was modified with 2-iminothiolane to introduce 4-mercaptobutyramidine groups, only a minor effect on the activity of the enzyme was observed. To retain the positive charges on the lysine residues of ETF, pyridyl disulphide structures were introduced by treating ETF with 2-iminothiolane in the presence of 2,2′-dithiodipyridyl. The electron-transfer activity of the resultant ETF preparation containing 4-(2-pyridyldithio)butyramidine (PDBA) groups was only slightly affected. When ETF-Q ox substituted with MBA groups was mixed with ETF bearing PDBA groups, at least 70% of the cross-links formed between the two proteins were between the small subunit of ETF and ETF-Q ox. ETF-Q ox, therefore, interacts predominantly with the same subunit of ETF as GAD. Variables which affect the selectivity of ETF-Q ox cross-linking to the subunits of ETF are considered.

scholarly journals Native cross-links in collagen fibrils induce resistance to human synovial collagenase

1979 ◽  
Vol 181 (3) ◽  
pp. 639-645 ◽  
Author(s):  
C A Vater ◽  
E D Harris ◽  
R C Siegel
Keyword(s):  
Lysyl Oxidase ◽  
Collagen Fibrils ◽  
Bone Collagen ◽  
Collagen Molecule ◽  
Cross Linking ◽  
Pathological Conditions ◽  
Insoluble Material ◽  
Induce Resistance ◽  
Cross Links

A model system consisting of highly purified lysyl oxidase and reconstituted lathyritic chick bone collagen fibrils was used to study the effect of collagen cross-linking on collagen degradation by mammalian collagenase. The results indicate that synthesis of approx. 0.1 Schiff-base cross-link per collagen molecule results in a 2–3-fold resistance to human synovial collagenase when compared with un-cross-linked controls or samples incubated in the presence of beta-aminopropionitrile to inhibit cross-linking. These results confirm previous studies utilizing artificially cross-linked collagens, or collagens isolated as insoluble material after cross-linking in vivo, and suggest that increased resistance to collagenase may be one of the earliest effects of cross-linking in vivo. The extent of intermolecular cross-linking among collagen fibrils may provide a mechanism for regulating the rate of collagen catabolism relative to synthesis in normal and pathological conditions.

EXPERIMENTAL VALIDATION OF THE CHARLESBY AND HORIKX MODELS APPLIED TO DE-VULCANIZATION OF SULFUR AND PEROXIDE VULCANIZATES OF NR AND EPDM

2016 ◽  
Vol 89 (4) ◽  
pp. 671-688 ◽  
Author(s):  
M. A. L. Verbruggen ◽  
L. van der Does ◽  
W. K. Dierkes ◽  
J. W. M. Noordermeer
Keyword(s):  
Experimental Validation ◽  
Main Chain ◽  
Sol Gel ◽  
Chain Scission ◽  
Cross Linking ◽  
Cross Link ◽  
Practical Reality ◽  
Cross Links ◽  
The Cross ◽  
Theoretical Considerations

ABSTRACT The theoretical model developed by Charlesby to quantify the balance between cross-links creation of polymers and chain scission during radiation cross-linking and further modifications by Horikx to describe network breakdown from aging were merged to characterize the balance of both types of scission on the development of the sol content during de-vulcanization of rubber networks. There are, however, disturbing factors in these theoretical considerations vis-à-vis practical reality. Sulfur- and peroxide-cured NR and EPDM vulcanizates were de-vulcanized under conditions of selective cross-link and random main-chain scissions. Cross-link scission was obtained using thiol-amine reagents for selective cleavage of sulfur cross-links. Random main-chain scission was achieved by heating peroxide vulcanizates of NR with diphenyldisulfide, a method commonly employed for NR reclaiming. An important factor in the analyses of these experiments is the cross-linking index. Its value must be calculated using the sol fraction of the cross-linked network before de-vulcanization to obtain reliable results. The values for the cross-linking index calculated with sol-gel data before de-vulcanization appear to fit the experimentally determined modes of network scission during de-vulcanization very well. This study confirms that the treatment of de-vulcanization data with the merged Charlesby and Horikx models can be used satisfactorily to characterize the de-vulcanization of NR and EPDM vulcanizates.

scholarly journals Localization of the Transglutaminase Cross-Linking Sites in the Bacillus subtilis Spore Coat Protein GerQ

2006 ◽  
Vol 188 (21) ◽  
pp. 7609-7616 ◽  
Author(s):  
Alicia Monroe ◽  
Peter Setlow
Keyword(s):  
Bacillus Subtilis ◽  
Coat Protein ◽  
Cross Linking ◽  
Spore Coat ◽  
Bacillus Subtilis Spore ◽  
Binding Partners ◽  
Lysine Residues ◽  
Cross Links ◽  
Hydrolysis Of ◽  
Spore Coat Protein

ABSTRACT The Bacillus subtilis spore coat protein GerQ is necessary for the proper localization of CwlJ, an enzyme important in the hydrolysis of the peptidoglycan cortex during spore germination. GerQ is cross-linked into high-molecular-mass complexes in the spore coat late in sporulation, and this cross-linking is largely due to a transglutaminase. This enzyme forms an ε-(γ-glutamyl) lysine isopeptide bond between a lysine donor from one protein and a glutamine acceptor from another protein. In the current work, we have identified the residues in GerQ that are essential for transglutaminase-mediated cross-linking. We show that GerQ is a lysine donor and that any one of three lysine residues near the amino terminus of the protein (K2, K4, or K5) is necessary to form cross-links with binding partners in the spore coat. This leads to the conclusion that all Tgl-dependent GerQ cross-linking takes place via these three lysine residues. However, while the presence of any of these three lysine residues is essential for GerQ cross-linking, they are not essential for the function of GerQ in CwlJ localization.

scholarly journals Bound (“Glassy”) Rubber as a Free Radical Cross-linked Rubber Layer on a Carbon Black

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1992 ◽  
Author(s):  
Alexey Kondyurin ◽  
Anastasia Eliseeva ◽  
Alexander Svistkov
Keyword(s):  
Free Radical ◽  
Carbon Black ◽  
Ion Beam ◽  
Cross Linking ◽  
Carbon Filler ◽  
Free Radical Reactions ◽  
Rubber Layer ◽  
Ion Beam Implantation ◽  
Cross Links ◽  
The Cross

A model of rubber with a cross-linked rubber layer on a carbon black filler has been proposed. The cross-links are the result of free radical reactions generated by carbon atoms with unpaired electrons at the edge of graphitic sheets in a carbon black filler. The experimental study of the cross-linking reactions in polyisoprene was done on a flat carbonized surface after ion beam implantation. The cross-linking process in the polyisoprene macromolecules between two particles was simulated. The model with a cross-linked rubber layer on a carbon filler as a “glassy layer” explains the mechanical properties of the rubber materials.

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