Dehydrate protein solution

Hydrates have further applications in bioengineering through the research of John and coworkers (Rao et al., 1990 Nguyen, 1991 Nguyen et al., 1991, 1993 Phillips et al., 1991). These workers have used hydrates in reversed micelles (water-in-oil emulsions) to dehydrate protein solutions for recovery and for optimization of enzyme activity, at nondestructive and low-energy conditions. 

Organic solvents also decrease protein solubility, but they are not as widely used as ammonium sulfate. They are thought to function as precipitating agents in two ways (1) by dehydrating proteins, much as ammonium sulfate does, and (2) by decreasing the dielectric constant of the solution. The organic solvents used (which, of course, must be miscible with water) include methanol, ethanol, and acetone. 

The practical solution to the protein stability dilemma is to remove the water. Lyophilization (freeze-drying) is most commonly used to prepare dehydrated proteins, which, theoretically, should have the desired long-term stability at ambient temperatures. However, as will be described in this review, recent infrared spectroscopic studies have documented that the acute freezing and dehydration stresses of lyophilization can induce protein unfolding [8-11]. Unfolding not only can lead to irreversible protein denaturation, even if the sample is rehydrated immediately, but can also reduce storage stability in the dried solid [12,13]. 

Polymers such as poly(ethyleneglycol) also serve to dehydrate proteins in solution as do salts, and they alter somewhat the dielectric properties in a manner similar to organic... 

Salting-out is not well understood. One popular explanation for this effect relies on the relative hydration of the protein versus bulk electrolyte. In this model, the electrolyte is assumed to bind bulk water as water of hydration near the ion s surface. Likewise, the protein needs to be hydrated with water. As the bulk electrolyte and the protein compete for bulk water to hydrate their respective surfaces, the protein become partially dehydrated and prefers to fill such exposed surface (dehydrated surface) with other protein molecules thus, facilitating crystal contacts. Thus, the solubility of the protein is reduced as the electrolyte is added to the protein solution. The effectiveness of ions (cations and anions) to cause phase separation (or lower solubility) has been documented by... 

Another critical consideration in protein delivery from hydrogel systems is the potential for protein denaturation in the device. For diffusion-controlled delivery systems, where water is the main transporting medium, the protein solution stability governs the type of device. Extended releasing times can be achieved with reservoir systems (Fig. 1) for highly stable proteins (Langer, 1990). Alternatively, dehydrated delivery systems... 

Plasma proteins are contraindicated in those with a history of allergic reactions to albumin, severe anemia, or cardiac failure in the presence of normal or increased intravascular volume and in patients on cardiopulmonary bypass. Plasma protein fractions are used cautiously in patients who are in shock or dehydrated and in those with congestive cardiac failure or hepatic or renal failure. These solutions are Pregnancy Category C drugp and are used cautiously during pregnancy and lactation. 

Protein recovery via disruption has also been achieved by adsorbing water from the w/o-ME solution, which causes protein to precipitate out of solution. Methods of water removal include adsorption using silica gel [73,151], molecular sieves [152], or salt crystals [58,163], or formation of clanthrate hydrates [154]. In most of the cases reported, the released protein appeared as a solid phase that, importantly, was virtually surfactant-free. In contrast to the dilution technique, it appears that dehydration more successfully released biomolecules that are hydrophilic rather than hydrophobic. 

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