Protein colloidal nature

This newly fermented wine is cloudy from suspended materials such as yeast, protein, colloids, and fine grape cellular solids. In storage, a natural clarification, or gravity settling out, of these materials takes place. 

Stradner, A., H. Sedgwick, F. Cardinaux, W. C. K. Poon, S. U. Egelhaaf, and P. Schnrtenberger. 2004. Equilibrium cluster formation in concentrated protein solutions and colloids. Nature. 432,492. 

To prevent aggregation of therapeutic proteins, the nature of the solutions used for reconstitution and for diluting them must be carefully chosen 5 % glucose solutions are not indicated. Sodium chloride solution has a limited use due to incompatibility with several active substances. For example, amphotericin B injection fluids cannot be diluted with sodium chloride and other electrolyte solutions because of the destabilisation of the colloidal systems. 

Proteins are natural polymeric surfactants. The importance of proteins in relation to food colloids and emulsions is so critical that thousands of studies have been... 

As it is now possible by choice of suitable conditions to prepare most compounds in this form, the colloid state should be considered as a physical state in which all substances can be made to exist. Many ma terials such as proteins, vegetable fibres, rubber, etc. are most stable or occur naturally in the colloidal slate. In the colloidal stale the properties of surface are all-important. 

Electroultrafiltration (EUF) combines forced-flow electrophoresis (see Electroseparations,electrophoresis) with ultrafiltration to control or eliminate the gel-polarization layer (45—47). Suspended colloidal particles have electrophoretic mobilities measured by a zeta potential (see Colloids Elotation). Most naturally occurring suspensoids (eg, clay, PVC latex, and biological systems), emulsions, and protein solutes are negatively charged. Placing an electric field across an ultrafiltration membrane faciUtates transport of retained species away from the membrane surface. Thus, the retention of partially rejected solutes can be dramatically improved (see Electrodialysis). 

The numerous separations reported in the literature include surfactants, inorganic ions, enzymes, other proteins, other organics, biological cells, and various other particles and substances. The scale of the systems ranges from the simple Grits test for the presence of surfactants in water, which has been shown to operate by virtue of transient foam fractionation [Lemlich, J. Colloid Interface Sci., 37, 497 (1971)], to the natural adsubble processes that occur on a grand scale in the ocean [Wallace and Duce, Deep Sea Res., 25, 827 (1978)]. For further information see the reviews cited earlier. 

An important technique for the qualitative and quantitative analysis of different macromolecular materiafs is based on the efectrophoretic separation of particfes having different transport vefocities (e.g., because they have different zeta potentiafs). This technique is used for the anafysis of proteins, pofysaccharides, and other naturally occurring substances whose molecular size approaches that of colloidal particles (for more details, see Section 30.3.4). It is an advantage of the electrophoretic method that mild experimental conditions can be used—dilute solutions with pH values around 7, room temperature, and so on—which are not destructive to the biological macromolecules. 

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