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

2012 ◽  
Vol 79 (4) ◽  
pp. 422-422
Keyword(s):  
Skim Milk ◽  
Cross Linking ◽  
Influence Of Temperature ◽  
Mineral Equilibria ◽  
The Individual

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 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.

scholarly journals Ultrasound-Assisted Transglutaminase Catalysis of the Cross-Linking and Microstructure of αs-Casein, β-Casein and κ-Casein

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1630
Author(s):  
Chun-Chi Chen ◽  
Liang-Yu Chen ◽  
Wen-Tai Li ◽  
Ken-Lin Chang ◽  
Hsien-Wei Tseng ◽  
...  
Keyword(s):  
Particle Size Analysis ◽  
Size Analysis ◽  
Cross Linking ◽  
Comprehensive Utilization ◽  
Transmission Electron ◽  
Microscopy Investigation ◽  
Electron Microscopy Investigation ◽  
Sds Page ◽  
The Cross ◽  
The Individual

The effects of ultrasonic treatment (UT)-assisted transglutaminase (TGase) catalysis on the physicochemical properties of individual αs-casein (αs-CN), β-casein (β-CN), and κ-casein (κ-CN) were investigated. After 60 min of incubation at 30 °C, αs-CN, β-CN, and κ-CN were cross-linked with TGase (6.0 units/mL), and high molecular weight polymers (>200 kDa) were formed. The use of TGase in conjunction with UT (20 kHz, power of 400 W, and amplitude 20%) led to an increase in the rate of αs-CN, β-CN, and κ-CN polymerization compared to the individual casein that contained TGase but did not undergo UT. SDS-PAGE scrutiny showed that the intensities of αs-CN, β-CN, and κ-CN incubation with regard to TGase and UT at 30 °C for 60 min noticeably decreased to 5.66 ± 0.39, 3.97 ± 0.43, and 26.07 ± 1.18%, respectively (p < 0.05). Particle size analysis results indicated that the molecule size appropriation for the cross-linking of αs-CN, β-CN, and κ-CN ranged from 6000 to 10,000 nm after 60 min incubation with TGase and UT. Transmission electron microscopy investigation showed network structures of cross-linking αs-CN, β-CN, and κ-CN were formed from αs-CN, β-CN, and κ-CN, respectively. As our results show, the comprehensive utilization of TGase and UT will be a superior method for the polymerization of αs-CN, β-CN, and κ-CN.

scholarly journals Optimized fragmentation improves the identification of peptides cross-linked using MS-cleavable reagents

2018 ◽  
Author(s):  
Christian E. Stieger ◽  
Philipp Doppler ◽  
Karl Mechtler
Keyword(s):  
Mass Spectrometry ◽  
Quality Data ◽  
Cross Linking ◽  
High Complexity ◽  
Mass Spectrometers ◽  
Acquisition Strategies ◽  
Cross Links ◽  
The Cross ◽  
The Individual

ABSTRACTCross-linking mass spectrometry (XLMS) is becoming increasingly popular, and current advances are widening the applicability of the technique so that it can be utilized by non-specialist laboratories. Specifically, the use of novel mass spectrometry-cleavable (MS-cleavable) reagents dramatically reduces complexity of the data by providing i) characteristic reporter ions and ii) the mass of the individual peptides, rather than that of the cross-linked moiety. However, optimum acquisition strategies to obtain the best quality data for such cross-linkers with higher energy C-trap dissociation (HCD) alone is yet to be achieved. Therefore, we have carefully investigated and optimized MS parameters to facilitate the identification of disuccinimidyl sulfoxide (DSSO)- based cross-links on HCD-equipped mass spectrometers. From the comparison of 9 different fragmentation energies we chose several stepped-HCD fragmentation methods that were evaluated on a variety of cross-linked proteins. The optimal stepped-HCD-method was then directly compared with previously described methods using an Orbitrap Fusion™ Lumos™ TribridTM instrument using a high-complexity sample. The final results indicate that our stepped-HCD method is able to identify more cross-links than other methods, mitigating the need for multistage MS (MSn) enabled instrumentation and alternative dissociation techniques.

scholarly journals P-loop Flexibility in Na+ Channel Pores Revealed by Single- and Double-cysteine Replacements

1997 ◽  
Vol 110 (1) ◽  
pp. 59-72 ◽  
Author(s):  
Robert G. Tsushima ◽  
Ronald A. Li ◽  
Peter H. Backx
Keyword(s):  
Double Mutant ◽  
Cross Linking ◽  
Na Channel ◽  
Na Channels ◽  
Rat Skeletal Muscle ◽  
Enhanced Sensitivity ◽  
Increased Sensitivity ◽  
The Individual ◽  
High Degree ◽  
Loop Flexibility

Replacement of individual P-loop residues with cysteines in rat skeletal muscle Na+ channels (SkM1) caused an increased sensitivity to current blockade by Cd2+ thus allowing detection of residues lining the pore. Simultaneous replacement of two residues in distinct P-loops created channels with enhanced and reduced sensitivity to Cd2+ block relative to the individual single mutants, suggesting coordinated Cd2+ binding and cross-linking by the inserted sulfhydryl pairs. Double-mutant channels with reduced sensitivity to Cd2+ block showed enhanced sensitivity after the application of sulfhydryl reducing agents. These results allow identification of residue pairs capable of approaching one another to within less than 3.5 Å. We often observed that multiple consecutive adjacent residues in one P-loop could coordinately bind Cd2+ with a single residue in another P-loop. These results suggest that, on the time-scale of Cd2+ binding to mutant Na+ channels, P-loops show a high degree of flexibility.

A multicomponent complex is required for the AAUAAA-dependent cross-linking of a 64-kilodalton protein to polyadenylation substrates

1990 ◽  
Vol 10 (3) ◽  
pp. 1244-1248 ◽  
Author(s):  
J Wilusz ◽  
T Shenk ◽  
Y Takagaki ◽  
J L Manley
Keyword(s):  
Uv Light ◽  
Cross Linking ◽  
Cross Link ◽  
Multicomponent Complex ◽  
Specificity Factor ◽  
The Individual ◽  
64 Kda Protein ◽  
Rna Interaction ◽  
Cleavage Stimulation Factor

A 64-kilodalton (kDa) polypeptide that is cross-linked by UV light specifically to polyadenylation substrate RNAs containing a functional AAUAAA element has been identified previously. Fractionated HeLa nuclear components that can be combined to regenerate efficient and accurate polyadenylation in vitro have now been screened for the presence of the 64-kDa protein. None of the individual components contained an activity which could generate the 64-kDa species upon UV cross-linking in the presence of substrate RNA. It was necessary to mix two components, cleavage stimulation factor and specificity factor, to reconstitute 64-kDa protein-RNA cross-linking. The addition of cleavage factors to this mixture very efficiently reconstituted the AAUAAA-specific 64-kDa protein-RNA interaction. The 64-kDa protein, therefore, is present in highly purified, reconstituted polyadenylation reactions. However, it is necessary to form a multicomponent complex to efficiently cross-link the protein to a substrate RNA.

Heat stability of recombined milk: influence of lecithins on the heat coagulation time-pH profile

1992 ◽  
Vol 59 (2) ◽  
pp. 177-185 ◽  
Author(s):  
Catharina H. McCrae ◽  
D. Donald Muir
Keyword(s):  
Milk Powder ◽  
Skim Milk ◽  
Heat Stability ◽  
Skim Milk Powder ◽  
Coagulation Time ◽  
Ph Profile ◽  
Mineral Equilibria ◽  
Soya Lecithin ◽  
Before And After ◽  
Wide Ph Range

SummaryTwo types of lecithin, namely egg and soya lecithin, were investigated as potential stabilizers of recombined milk. They were incorporated into recombined milk both before and after homogenization (20·7 MPa; 60 °C). Their presence at homogenization changed neither mineral equilibria nor homogenization efficiency. However, heat stability varied significantly irrespective of batch of low-heat skim milk powder used in recombined milk. The variation in heat stability depended on type of lecithin. Soya lecithin proved to be a very effective stabilizer. It improved heat stability over a wide pH range (6·3–7·1) and the effect occurred even when the lecithin was added after homogenization. In contrast, egg lecithin destabilized the system to heat at pH < 6·7 by converting a Type A into a Type B heat coagulation time-pH profile if it was incorporated before homogenization; after homogenization it had no effect. The effects of both egg and soya lecithin on the heat stability of recombined milk strongly suggest that interactions occur between phospholipids and milk protein.

Some aspects of the ethanol stability of caprine milk

1982 ◽  
Vol 49 (3) ◽  
pp. 459-468 ◽  
Author(s):  
David S. Horne ◽  
Thomas G. Parker
Keyword(s):  
Calcium Phosphate ◽  
Chemical Modification ◽  
Milk Protein ◽  
Bovine Milk ◽  
Skim Milk ◽  
Ph Profile ◽  
Caprine Milk ◽  
Colloidal Calcium Phosphate ◽  
The Individual ◽  
Ethanol Stability

SUMMARYCaprine skim-milk exhibits markedly lower ethanol (EtOH) stability than bovine skim-milk but can still be characterized by a sigmoidal pH profile. As with bovine milk, the position of this profile along the pH-axis was found to be sensitive to available Ca levels. Manipulation of salt levels, either by serum interchange, addition or diminution did not result in any significant increase in the EtOH stability high pH asymptote, Smax, and reduction of the colloidal calcium phosphate of caprine milk also had no significant effect. EtOH stability/pH profiles similar to those of bovine milk were achieved only by chemical modification of the caprine milk protein by reaction with aldehydes and anhydrides. It is concluded that the low EtOH stability of caprine milk as compared with bovine milk is due to the different proportions of the individual caseins present, in particular the lack of an αsl-casein homologue in caprine milk.

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