A protein stability

Dickinson, E., Pawlowsky, K. (1997) Effect of i-carrageenan on flocculation, creaming, and rheology of a protein-stabilized emulsion. Journal of Agricultural and Food Chemistry, 45, 3799-3806. 

For a colloidal system containing a mixture of different biopolymers, in particular a protein-stabilized emulsion containing a hydrocolloid thickening agent, it is evident that the presence of thermodynamically unfavourable interactions (A u > 0) between the biopolymers, which increases their chemical potentials (thermodynamic activity) in the bulk aqueous phase, has important consequences also for colloidal structure and stability (Antipova and Semenova, 1997 Antipova et al., 1997 Dickinson and Semenova, 1992 Dickinson et al., 1998 Pavlovskaya et al., 1993 Tsap-kina et al., 1992 Semenova et al., 1999a Makri et al., 2005 Vega et al., 2005 Semenova, 2007). 

There seems to be a sort of analogy here with the arrested phase separation of a protein-stabilized depletion-flocculated emulsion containing a thermodynamically incompatible hydrocolloid like xanthan gum (Moschakis et al., 2005 Dickinson, 2006b). 

Figure 7.16 Dependence on tlie polysaccharide concentration CDS of (a) tlie second virial coefficient A2 and (b) tlie stmcture-sensitive parameter p of complexes of sodium caseinate + dextran sulfate , complexes prepared in bulk solution a, complexes prepared at tlie interface in a protein-stabilized foam , sodium caseinate alone. Reproduced from Semenova et al. (2009) with permission.

Dickinson, E., Owusu, R.K., Williams, A. (1993b). Orthokinetic destabilization of a protein-stabilized emulsion by a water soluble surfactant. Journal of the Chemical Society, Faraday Transactions, 89, 865-866. 

The potential for a protein-stabilizing solute like glycerol to influence metabolic rates stems... 

C) mixtures. Whereas in the first mixture lysozyme is in its native state, in the second (at pH 2.0), it undergoes a transition to a denaturated state between 2.5 and 5.0 M urea. The water + lysozyme + glucose mixture was also considered because, in contrast to urea, glucose is a protein stabilizer. ... 

Emulsion stability is required in many dairy applications, but not all. In products like whipped cream and ice cream, the emulsion must be stable in the liquid form but must partially coalesce readily upon foaming and the application of shear. The structure and physical properties of whipped cream and ice cream depend on the establishment of a fat-globule network. In cream whipped to maximum stability, partially coalesced fat covers the air interface. In ice cream, partially coalesced fat exists both in the serum phase and at the air interface also, there is more globular fat at the air interface with increasing fat destabilization. Partial coalescence occurs due to the collisions in a shear field of partially crystalline fat-emulsion droplets with sufficiently-weak steric stabilization (low level of surface adsoiption of amphiphilic material to the interface per unit area). To achieve optimal fat crystallinity, the process is very dependent on the composition of the triglycerides and the temperature. It is also possible to manipulate the adsorbed layer to reduce steric stabilization to an optimal level for emulsion stability and rapid partial coalescence upon the application of shear. This can be done either by addition of a small-molecule surfactant to a protein-stabilized emulsion or by a reduction of protein adsorption to a minimal level through selective homogenization. 

Protein purification, introduced in the 1990s, produced high-purity concentrates with increased amounts of factor VIII or factor IX relative to the product s total protein content. Recombinant factor VIII and then factor IX also became available. The first-generation recombinant factor VIII products utilize human and animal proteins in culture and add human albumin as a protein stablilizer. Second-generation recombinant factor VIII concentrates removed albumin as a protein stabilizer, and the third-generation products lack human and animal proteins in the culture media. Finally, gene therapy for the treatment of hemophilia is now in the early stages of clinical trials. 

Augusto, O., K.L. Kunze, and P.R. Ortiz de Monteiiano (1982). N-Phenylprotoporphyrin IX formation in the hemoglobin-phenylhydrazine reaction Evidence for a protein-stabilized iron-phenyl intermediate. J. Biol. Chem. 257, 6231-6241. 

In the contrast to the S. shibatae enzyme, the P. furiosus DNA topoisomerase VI needs the presence of a protein stabilizer in the reaction medium. In the absence of 0.5 M potassium glutamate, no activity was detectable. This strong stabilization effect of potassium glutamate has already been observed for other extreme... 

Figure 5.15 Schematic representation of production of oil-in-water emulsions containing droplets stabilized by two layers (protein-polysaccharide). A protein-stabilized emulsion is formed first, and then an oppositely charged polysaccharide is mixed with this emulsion.

Figure 13.15 Hydrophilic groups on the surlace of a large molecule such as a protein stabilize the molecule in water. Note that all the hydrophilic groups can form hydrogen bonds with water.

Unlike some dispersions of small colloidal particles, the bridging polymers in most emulsion systems are usually smaller in size than the emulsion droplets. Hence, the flocculation mechanisms of polymer bridging and polymer cross-linking are not so distinctive. In the case of a protein-stabilized emulsion, the droplets may... 

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