Susceptibility of the individual caseins in reconstituted skim milk to cross-linking by transglutaminase: influence of temperature, pH and mineral equilibria

2012 ◽  
Vol 79 (4) ◽  
pp. 414-421 ◽  
Author(s):  
Katharina Hinz ◽  
Thom Huppertz ◽  
Alan L. Kelly
Keyword(s):  
Calcium Chloride ◽  
Colloidal Stability ◽  
Incubation Temperature ◽  
Skim Milk ◽  
Trisodium Citrate ◽  
Cross Linking ◽  
Mineral Equilibria ◽  
Tgase Activity ◽  
The Individual ◽  
Increasing Temperature

The susceptibility of total casein and the individual caseins in reconstituted skim milk to transglutaminase (TGase)-induced cross-linking was studied as a function of incubation temperature (5–40 °C), pH (5·0–7·0) and mineral addition. Within the ranges studied, the level of total casein cross-linked increased with increasing temperature, pH and concentration of added trisodium citrate, whereas adding calcium chloride had the opposite effect. These effects can be largely related to the effects of these parameters on TGase activity. In addition, the parameters were also found to influence the susceptibility of κ-casein, and to a lesser extent β-casein, to cross-linking, whereas the susceptibility of αs1-casein was not affected. The susceptibility of κ-casein to cross-linking increased with increasing temperature and calcium chloride addition, but decreased with increasing pH and citrate content, whereas the susceptibility of β-casein to TGase-induced cross-linking decreased with increasing temperature, but was not affected by other parameters. These findings highlight the fact that selection of environmental conditions during cross-linking can be applied to tailor the surface, and hence possibly colloidal stability, of casein micelles in TGase-treated milk.

scholarly journals Combined Use of Trisodium Citrate and Transglutaminase to Enhance the Stiffness and Water-Holding Capacity of Acidified Yak Milk Gels

2018 ◽  
Vol 2018 ◽  
pp. 1-6
Author(s):  
Lin Yang
Keyword(s):  
Electron Microscopy ◽  
Synergistic Effect ◽  
Skim Milk ◽  
Textural Properties ◽  
Trisodium Citrate ◽  
Water Holding Capacity ◽  
Cross Linking ◽  
Yak Milk ◽  
Combined Use ◽  
Water Holding

In this research, the synergistic effect of trisodium citrate (TSC) and microbial transglutaminase (TGase) treatment on the textural properties of acidified yak skim milk gels was investigated. TSC was added to yak skim milk to concentrations of 0, 20, and 40 mmol/L, followed by adjusting the pH to 6.7. The samples were incubated with TGase for the cross-linking reaction, after which the samples were acidified with 1.4% (w/v) gluconodelta-lactone (GDL) at 42°C for 4 h to form gels. The stiffness and water holding capacity (WHC) of gels exhibited higher values at 20 or 40 mmol/L than without TSC. The final storage modulus (G′) of yak milk gels was positively related to the concentration of TSC prior to TGase treatment. Cryoscanning electron microscopy observations showed that the gel networks were more rigid with higher TSC concentrations. Overall, TSC dissociated particles in yak milk into smaller ones. The newly formed particles in yak skim milk could form acid-induced gels with greater stiffness and higher WHC in the presence of TGase.

scholarly journals Photosensitization to ultraviolet irradiation and selective killing of cells following uptake of pyrene-containing fatty acid

1986 ◽  
Vol 85 (1) ◽  
pp. 149-159
Author(s):  
E. Fibach ◽  
O. Morand ◽  
S. Gatt
Keyword(s):  
Fatty Acid ◽  
Ultraviolet Irradiation ◽  
Plasma Membranes ◽  
Incubation Temperature ◽  
Serum Proteins ◽  
Neutral Lipids ◽  
Cell Types ◽  
Dodecanoic Acid ◽  
A Cell ◽  
The Individual

Cells were incubated with 12-(1-pyrene)-dodecanoic acid (P12), a long-chain fatty acid to which a pyrene ring has been attached covalently. This acid was transported across the plasma membranes of cells and subsequently incorporated into their neutral lipids and phospholipids. Irradiation of these pyrene-containing cells for short periods (0.5-4 min) with ultraviolet light at 366 nm resulted in eventual cell death. Similar irradiation had no effect on cells that had not been exposed to P12. The time of the period of irradiation necessary for inducing the toxic process was related to the quantity of P12 incorporated, the latter being a function of the respective metabolic activity of the individual cell type. The degree of incorporation of P12 into a cell, and consequently its acquired sensitivity to killing by ultraviolet irradiation at 366 nm, was affected by the incubation temperature and addition of non-fluorescent fatty acid, albumin or other serum proteins. Different degrees of incorporation of P12 into various cell types were used for selective killing and elimination of cell populations by irradiation at 366 nm. The combined procedure of preincubation with P12 followed by ultraviolet irradiation thus permitted selection of cell types with a greater resistance to this procedure.

Hydrogels based on waterborne poly(urethane-urea)s by physically cross-linking with sodium alginate and calcium chloride

2020 ◽  
Vol 250 ◽  
pp. 116940
Author(s):  
Iñigo Díez-García ◽  
Monica Rosas de Costa Lemma ◽  
Hernane S. Barud ◽  
Arantxa Eceiza ◽  
Agnieszka Tercjak
Keyword(s):  
Sodium Alginate ◽  
Calcium Chloride ◽  
Cross Linking

Role of Trisodium Citrate in the Unclottability by Thrombin of Fibrinogen Metz

1975 ◽  
Author(s):  
C. Soria ◽  
J. Soria ◽  
M. Samama ◽  
E. Poirot ◽  
G. Kling
Keyword(s):  
Calcium Chloride ◽  
Whole Blood ◽  
Blood Clotting ◽  
Negative Charge ◽  
Trisodium Citrate ◽  
Thrombin Time ◽  
Clotting Time ◽  
Fibrin Formation ◽  
Blood Clotting Time

In a case of homozygous dysfibrinogenemia, the whole blood clotting time was moderately prolonged, while the thrombin clotting time was infinite, whatever dose or nature of thrombin used. Besides, the bleeding syndrome in this case was very weak.We observed also that only after trisodium citrate addition to purified fibrinogen, the abnormal fibrinogen became unclottable by thrombin even after addition of calcium chloride, since without trisodium citrate thrombin time was only prolonged.By immunoelectrophoresis and by isofocusing in the presence or in the absence of trisodium citrate, we therefore undertook to show that trisodium citrate reacts more strongly with the abnormal fibrinogen than with normal one. Thus, trisodium citrate conferring a negative charge to the pathological molecule, the abnormal fibrinogen became resistant to clotting with thrombin. Protamine sulfate, by positiving the charges of fibrinogen, partially corrects the defect in fibrin formation.

Experimental characterization and computational modeling of hydrogel cross-linking for bioprinting applications

2019 ◽  
Vol 42 (10) ◽  
pp. 548-557 ◽  
Author(s):  
Aidin Hajikhani ◽  
Franca Scocozza ◽  
Michele Conti ◽  
Michele Marino ◽  
Ferdinando Auricchio ◽  
...  
Keyword(s):  
Calcium Chloride ◽  
Reaction Diffusion ◽  
Chloride Diffusion ◽  
Chemical System ◽  
Cross Linking ◽  
Modeling Framework ◽  
Reaction Diffusion Model ◽  
Constant Diffusivity ◽  
Low Toxicity ◽  
Element Discretizations

Alginate-based hydrogels are extensively used to create bioinks for bioprinting, due to their biocompatibility, low toxicity, low costs, and slight gelling. Modeling of bioprinting process can boost experimental design reducing trial-and-error tests. To this aim, the cross-linking kinetics for the chemical gelation of sodium alginate hydrogels via calcium chloride diffusion is analyzed. Experimental measurements on the absorbed volume of calcium chloride in the hydrogel are obtained at different times. Moreover, a reaction-diffusion model is developed, accounting for the dependence of diffusive properties on the gelation degree. The coupled chemical system is solved using finite element discretizations which include the inhomogeneous evolution of hydrogel state in time and space. Experimental results are fitted within the proposed modeling framework, which is thereby calibrated and validated. Moreover, the importance of accounting for cross-linking-dependent diffusive properties is highlighted, showing that, if a constant diffusivity property is employed, the model does not properly capture the experimental evidence. Since the analyzed mechanisms highly affect the evolution of the front of the solidified gel in the final bioprinted structure, the present study is a step towards the development of reliable computational tools for the in silico optimization of protocols and post-printing treatments for bioprinting applications.

scholarly journals Impact of expected global warming on C mineralization in maritime Antarctic soils: results of laboratory experiments

2010 ◽  
Vol 22 (5) ◽  
pp. 485-493 ◽  
Author(s):  
Juliana Vanir de Souza Carvalho ◽  
Eduardo de Sá Mendonça ◽  
Rui Tarcísio Barbosa ◽  
Efrain Lázaro Reis ◽  
Paulo Negrais Seabra ◽  
...  
Keyword(s):  
Organic Matter ◽  
Humic Substances ◽  
Humic Acids ◽  
Incubation Temperature ◽  
Structural Characteristics ◽  
Maritime Antarctic ◽  
Organic C ◽  
Antarctic Soils ◽  
Mineral Soils ◽  
Increasing Temperature

AbstractThis study concerned the fragility of maritime Antarctic soils under increasing temperature, using the C dynamics and structural characteristics of humic substances as indicators. Working with four representative soils from King George Island (Lithic Thiomorphic Cryosol (LTC1 and LTC2), Ornithogenic Cryosol (OG) and Gelic Organosol (ORG)) we evaluated the total organic C and nitrogen contents, the oxidizable C and humic substances. Soil samples were incubated to assess the amount of C potentially mineralizable at temperatures typical of an Antarctic summer (5–14°C). Humic acids showed a higher aliphatic character and a smaller number of condensed aromatic groups, which suggests that these molecules from Antarctic soils are generally less resistant to microbial degradation than humic acids molecules from other regions. Based on 13C NMR spectra of MAS and CP/MAS, samples of soil humic acids of mineral soils (LTC1 and LTC2) have a higher content of aliphatic C, and heteroatom C, with lower levels of carbonyl and aromatic C, when compared with organic matter-rich soils (OG and ORG). Increasing incubation temperature led to a higher rate of mineralizable C in all soils. A sequence of soil fragility was suggested - LTC1 and LTC2 > OG > ORG - which showed a correlation with the Q10 coefficient and the ratio of labile and recalcitrant C fractions of soil organic matter (R2 = 0.83).

Growth of Staphylococcus aureus in Milks and Creams with Various Amounts of Milk Fat

1989 ◽  
Vol 52 (8) ◽  
pp. 540-543 ◽  
Author(s):  
MARGARET I. HALPIN-DOHNALEK ◽  
ELMER H. MARTH
Keyword(s):  
Staphylococcus Aureus ◽  
Milk Fat ◽  
Incubation Temperature ◽  
Skim Milk ◽  
Fold Increase ◽  
Fat Content ◽  
Strain Variation ◽  
High Fat ◽  
Whole Milk

Staphylococcus aureus strains 100-A, 196-E, 254, 473, 505, and 521 generally grew better in skim milk and whole milk (3.5% milk fat) than in light cream (18% milk fat) and heavy whipping cream (36% milk fat) at 25 and 37°C. S. aureus strains grew to greater than 106/ml from an inoculum of ca. 103/ml in skim and whole milk held at 37°C. From the same level of inoculum, strains grew to 106–107/ml in light cream held at 37°C. A 10 to 100-fold increase in population was observed for most strains in heavy whipping cream inoculated with ca. 104 S. aureus/ml and held at 37°C. Less than a 10-fold increase in population was noted for strain 254 in heavy whipping cream held at 37°C. When strains of S. aureus were inoculated into milks and creams and held at 25°C, populations of the pathogen increased approximately 100-fold in skim and whole milk and 10-fold or less in light cream and heavy whipping cream. S. aureus was enumerated using Chapman Stone, Mannitol Salt, Baird-Parker, and Vogel-Johnson agars; best results were obtained with Baird-Parker and Vogel-Johnson agars, particularly when high-fat fluid products were tested. Milk fat content, incubation temperature, and strain variation influenced the ability of S. aureus to grow in various dairy fluids.

scholarly journals Structures of the Gβ-CCT and PhLP1–Gβ-CCT complexes reveal a mechanism for G-protein β-subunit folding and Gβγ dimer assembly

2015 ◽  
Vol 112 (8) ◽  
pp. 2413-2418 ◽  
Author(s):  
Rebecca L. Plimpton ◽  
Jorge Cuéllar ◽  
Chun Wan J. Lai ◽  
Takuma Aoba ◽  
Aman Makaju ◽  
...  
Keyword(s):  
G Protein ◽  
Unnatural Amino Acid ◽  
Cross Linking ◽  
G Protein Signaling ◽  
Protein Signaling ◽  
Cryo Electron Microscopy ◽  
Functional Complex ◽  
The Individual ◽  
Insight Into ◽  
Chemical Cross Linking

G-protein signaling depends on the ability of the individual subunits of the G-protein heterotrimer to assemble into a functional complex. Formation of the G-protein βγ (Gβγ) dimer is particularly challenging because it is an obligate dimer in which the individual subunits are unstable on their own. Recent studies have revealed an intricate chaperone system that brings Gβ and Gγ together. This system includes cytosolic chaperonin containing TCP-1 (CCT; also called TRiC) and its cochaperone phosducin-like protein 1 (PhLP1). Two key intermediates in the Gβγ assembly process, the Gβ-CCT and the PhLP1–Gβ-CCT complexes, were isolated and analyzed by a hybrid structural approach using cryo-electron microscopy, chemical cross-linking coupled with mass spectrometry, and unnatural amino acid cross-linking. The structures show that Gβ interacts with CCT in a near-native state through interactions of the Gγ-binding region of Gβ with the CCTγ subunit. PhLP1 binding stabilizes the Gβ fold, disrupting interactions with CCT and releasing a PhLP1–Gβ dimer for assembly with Gγ. This view provides unique insight into the interplay between CCT and a cochaperone to orchestrate the folding of a protein substrate.

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