Protein denaturation minimization

An efficient cooling system minimizes protein denaturation (denaturation would otherwise occur due to the considerable amount of heat generated during the homogenization process). Ho-mogenizers capable of handling large quantities of cellular suspensions are now available, many of which can efficiently process several thousand litres per hour. 

All samples must be stored appropriately to minimize the loss of activity due to protein denaturation, lack of stabilizers or presence of inhibitors. Optimal storage conditions will vary for different enzymes and the nature of the sample, blood, tissue, etc. Such information would be sought from specialist textbooks. 

The simplest approach to minimizing protein-wall interaction is to use a buffer pH at which interactions do not occur. At acidic pH the silanols on the surface of the capillary are protonated, and the net charge of the proteins is positive. At high pH, the wall is negatively charged, and so are the sample components. Both conditions result in electrostatic repulsion. Problems associated with operation at pH extremes include the potential instability of proteins (denaturation, degradation, and precipitation) and the limited pH range in which to achieve resolution. Additionally, operation at extreme pH does not eliminate all nonspecific interactions. 

NFDM, which retains casein micelles similar to those in fresh milk, is produced by pasteurization of sklmmllk, vacuum concentration and spray drying under processing conditions that result in either "low heat" or "high heat" product. Low heat NFDM is required for most applications that depend upon a highly soluble protein, as the case for most emulsification applications, since it is manufactured under mild temperature conditions to minimize whey protein denaturation and complexation with casein micelles. 

Whey protein concentrates (WPC) are produced by a variety of processing treatments to remove both lactose and minerals (20) as indicated in Figure 5. Even though it would be highly desireable to remove most of the lactose and minerals in these processes, it is not practical from an economic standpoint and thus most of these products only range in protein content from 35 to 50 %.The major objective of most of these processes is to produce a WPC with minimal protein denaturation in order to obtain a product with maximum protein solubility and functionality. However, from a practical consideration this objective is not readily obtainable, and thus most WPC products commercially available exhibit variable whey protein denaturation and functionality (20). 

Whey protein concentrates (WPC), which are relatively new forms of milk protein products available for emulsification uses, have also been studied (4,28,29). WPC products prepared by gel filtration, ultrafiltration, metaphosphate precipitation and carboxymethyl cellulose precipitation all exhibited inferior emulsification properties compared to caseinate, both in model systems and in a simulated whipped topping formulation (2. However, additional work is proceeding on this topic and it is expected that WPC will be found to be capable of providing reasonable functionality in the emulsification area, especially if proper processing conditions are followed to minimize protein denaturation during their production. Such adverse effects on the functionality of WPC are undoubtedly due to their Irreversible interaction during heating processes which impair their ability to dissociate and unfold at the emulsion interface in order to function as an emulsifier (22). 

The extraction of an intracellular protein usually involves a compromise between recovery and purity. Optimization of the extraction conditions should maximize the release of the target protein, while minimizing the contaminants, which may be difficult to remove. For this, it is important to determine the conditions under which denaturation or degradation occurs. 

The definition of a more efficient enzymatic system could be based on the separation of the catalytic cycle of the enzyme and the degradation step by the Mn3+ reactive species in MnP systems. The Mn3+-chelates present several advantages in their use as oxidants. They are more tolerant to protein denaturing conditions such as extremes of temperature, pH, oxidants, organic solvents, detergents, and proteases, and they are smaller than proteins therefore, they can penetrate microporous barriers inaccessible to proteins. The optimization of the production of the Mn3+-chelate will have to be compatible with the minimal consumption and deactivation of the enzyme. 

Surfactants are added to formulations to minimize denaturation of the protein at interfaces, typically liquid/air, solid/air, and liquid/container interfaces. Surfactants bind to hydrophobic areas of proteins. By minimizing the accessibility of the hydro-phobic contacts in a protein solution, the surfactant reduces the protein-protein interactions that lead to... 

In order to minimize protein-protein interactions the concentration of protein is kept as low as possible, but high enough to permit practical large-scale processing. Concentration of the organic solvent (mostly ethanol) and the temperature are maintained as low as possible in order to minimize protein denaturation. The mole fractions of ethanol in the mixture do not generally exceed 0.163, and the temperature is maintained between 0°C and the freezing point. Concen-... 

Ammonium sulfate, (NH4)2S04, is the most commonly used compound for salting out of proteins because it is very soluble (706 g/L) and has four ionic charges per molecule. Precipitations are generally performed slowly with cold solutions to minimize protein denaturation due to the heat... 

They must have high oxygen and carbon dioxide permeability. They should be chemically stable without leachable moieties and be blood compatible, minimizing thrombosis, platelet activation and injury, and protein denaturation. 

The solubility of the protein is minimal at the isoelectric point. Also, because protein shape is determined very much by intramolecular electrical attraction (see Section 3.8), the shapes of proteins can be dramatically altered by pH. Such abnormally shaped proteins are called denatured and no longer function for their intended purposes. 

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