The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Ruben Mercadeprieto - One of the best experts on this subject based on the ideXlab platform.
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effect of n ethylmaleimide as a blocker of disulfide crosslinks formation on the alkali cold gelation of whey proteins
PLOS ONE, 2016Co-Authors: Zhao Lei, Xiao Dong Chen, Ruben MercadeprietoAbstract:N-ethylmaleimide (NEM) was used to verify that no new disulfide crosslinks were formed during the fascinating rheology of the alkali cold-gelation of whey proteins, which show Sol-Gel-Sol transitions with time at pH > 11.5. These dynamic transitions involve the formation and subsequent destruction of non-covalent interactions between soluble whey aggregates. Therefore, incubation of aggregates with NEM was expected not to affect much the rheology. Experiments show that very little additions of NEM, such as 0.5 mol per mol of protein, delayed and significantly strengthened the metastable gels formed. Interactions between whey protein aggregates were surprisingly enhanced during incubation with NEM as inferred from oscillatory rheometry at different protein concentrations, dynamic swelling, Trp fluorescence and SDS-PAGE measurements.
Stephen R. Decker - One of the best experts on this subject based on the ideXlab platform.
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Saturation molalities and standard molar enthalpies of solution of α-d-xylose(cr) in H2O(l); standard molar enthalpies of solution of 1,4-β-d-xylobiose(am), and 1,4-β-d-xylotriose(am) in H2O(l)
The Journal of Chemical Thermodynamics, 2012Co-Authors: Robert N. Goldberg, Brian E. Lang, Bruce Coxon, Stephen R. DeckerAbstract:Abstract The saturation molality of α- d -xylose(cr) in water was measured by using HPLC and is m(sat) = (8.43 ± 0.42) mol · kg−1 at T = 298.15 K. It was also established that the anhydrous form of α- d -xylose(cr) is the crystalline form that is in equilibrium with the aqueous solution at T = 298.15 K. Solution calorimetry was used to measure the following standard molar enthalpies of solution at T = 298.15 K: Δ sol H m ∘ = (12.10 ± 0.12) kJ · mol−1 for α- d -xylose(cr); Δ sol H m ∘ = −(8.1 ± 2.7) kJ · mol−1 for 1,4-β- d -xylobiose(am); and Δ sol H m ∘ = −(24.1 ± 6.4) kJ · mol−1 for 1,4-β- d -xylotriose(am). It was observed that both 1,4-β- d -xylobiose(am) and 1,4-β- d -xylotriose(am) were amorphous substances and that they form thick gels in water in which no solid phase is present. Consequently, it is not possible to measure m(sat) for these two substances. All substances were carefully characterized by using both HPLC and Karl Fischer analysis. NMR was used to measure the anomeric purity of the α- d -xylose(cr). Thermodynamic network calculations were used to calculate standard molar formation properties for the aforementioned substances.
Johan Borgström - One of the best experts on this subject based on the ideXlab platform.
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Rheology of kappa-carrageenan in mixtures of sodium and cesium iodide : two types of gels
Carbohydrate Polymers, 1996Co-Authors: Ioannis S. Chronakis, Lennart Piculell, Johan BorgströmAbstract:Abstract Recent studies on dilute solutions (Borgstrom et al. (1996), Int. J. Biol. Macromol. 18 , 223) have shown that kappa-carrageenan helices associate into superhelical rigid rods in mixed 0.1 M aqueous solutions of NaI and CsI above a critical mole fraction ( x Cs = 0.4) of Cs. This work concerns the temperature-dependent rheology of more concentrated systems in mixed and pure solutions of the same salts. Gels with low moduli were even found in NaI alone, although this salt is known to impede the gelation of kappa-carrageenan, but only above 0.9% (w/w) of carrageenan. These gels were reminiscent of iota-carrageenan gels in two respects: the (low) magnitude of the shear storage modulus ( G ′), and the absence of hysteresis in the sol-gel transition. On the other hand, both the threshold concentration for gelation and the ratio between the loss and storage moduli were substantially higher for the kappa-carrageenan gels in NaI. In mixed solutions of CsI and NaI, two types of kappa-carrageenan gels could be distinguished, depending on the cesium content. The transition occurred at x Cs = 0.4, as in the previous studies on dilute solutions. Below x Cs = 0.4, the gels were similar to those in NaI alone. Above x Cs = 0.4, the gels were similar to ‘conventional’ kappa-carrageenan gels, formed in salts such as KC1: a pronounced thermal hysteresis appeared in the sol-gel transition, the gels showed tendencies for syneresis, and G ′ increased dramatically with increasing cesium content.
Zhao Lei - One of the best experts on this subject based on the ideXlab platform.
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effect of n ethylmaleimide as a blocker of disulfide crosslinks formation on the alkali cold gelation of whey proteins
PLOS ONE, 2016Co-Authors: Zhao Lei, Xiao Dong Chen, Ruben MercadeprietoAbstract:N-ethylmaleimide (NEM) was used to verify that no new disulfide crosslinks were formed during the fascinating rheology of the alkali cold-gelation of whey proteins, which show Sol-Gel-Sol transitions with time at pH > 11.5. These dynamic transitions involve the formation and subsequent destruction of non-covalent interactions between soluble whey aggregates. Therefore, incubation of aggregates with NEM was expected not to affect much the rheology. Experiments show that very little additions of NEM, such as 0.5 mol per mol of protein, delayed and significantly strengthened the metastable gels formed. Interactions between whey protein aggregates were surprisingly enhanced during incubation with NEM as inferred from oscillatory rheometry at different protein concentrations, dynamic swelling, Trp fluorescence and SDS-PAGE measurements.
Raymond L. Legge - One of the best experts on this subject based on the ideXlab platform.
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Study of support materials for sol-gel immobilized lipase
Biocatalysis and Biotransformation, 2013Co-Authors: Sarah M. Meunier, Raymond L. LeggeAbstract:AbstractA variety of support materials for sol-gel immobilized lipase were considered based on their ability to provide superior sol-gel adhesion, load protein, and synthesize methyl oleate. A standard approach was developed to formulate the supported lipase Sol-Gels and to allow comparison of the resulting hybrid materials. These supported Sol-Gels are proposed as an alternative immobilization regime to overcome some challenges associated with enzymatic biodiesel production such as enzyme stability and cost. The support materials considered were 6–12 mesh silica gel, Celite® R633, Celite® R632, Celite® R647, anion-exchange resin AG3-X4, and Quartzel® felt. Each support material exhibited unique properties that would be beneficial for this application including: Quartzel® felt had the highest initial sol-gel capacity (62.5 mL/g) and sol-gel adhesion (1100 mg sol-gel/g material); silica gel had the most uniform coating of deposited sol-gel; the anion-exchange resin AG3-X4 supported sol-gel had the highest ...
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evaluation of diatomaceous earth as a support for sol gel immobilized lipase for transesterification
Journal of Molecular Catalysis B-enzymatic, 2010Co-Authors: Sarah M. Meunier, Raymond L. LeggeAbstract:Abstract Enzymatic production of biodiesel by triglyceride transesterification is a promising alternative to chemically catalyzed biodiesel production despite the challenges involved with using enzymes. Celite ® supported lipase sol–gels were investigated as an option for solving some of the challenges associated with the use of enzymes for biodiesel production addressing such problems as activity, stability and reusability of the enzyme. Three types of Celite ® were considered (R633, R632, and R647) and compared to unsupported lipase sol–gels. Various factors were considered with regard to comparing the support materials. They included surface morphology characterized using surface area analysis and scanning electron microscopy, physical properties including adhesion of the sol–gel to the Celite ® and the protein loading on the Celite ® , and finally enzymatic properties based on the conversion of methanol to methyl oleate and the enzymatic activity of lipase. All the sol–gels showed good conversion and initial lipase activity, and all the Celite ® supports had similar sol–gel adhesion and protein loading. Sol–gel immobilized lipase supported on Celite ® R632 had an average 6-h percent conversion of approximately 60%, and an average initial lipase activity comparable to that of the unsupported sol–gel formulation.