Electrophoresis Is Used for Resolving Mixtures

I Gel electrophoresis is the best way to analyze mix-Vr-j tures and assess purity. Gel electrophoresis separates proteins according to their size and their charge. It is almost always performed in aqueous solution supported by a gel system. The gel is a loosely cross-linked network that functions to stabilize the protein boundaries between the protein and the solvent, both during and after electrophoresis, so that they may be stained or otherwise manipulated. 

The most popular method of electrophoretic separation by gels employs sodium dodecyl sulfate (SDS). This method not only gives an index of protein purity but yields an estimate of the protein subunit molecular weights. The mixture of proteins to be characterized is first completely denatured by adding SDS (a detergent) and mercaptoethanol and by briefly heating the mixture. Denaturation is caused by the association of the apolar tails of the SDS molecules with protein hydrophobic groups. Any cystine disulfide 

Although electrophoresis is the method of choice for assessing protein purity, it is not frequently used as a purification step, at least not yet. This is because of the small amounts that can usually be analyzed and because of the denaturing conditions that are often used in electrophoretic analysis. 

Sedimentation and Diffusion Are Used for Size and Shape Determination 

WWe have seen that sedimentation by centrifugation is used for protein purification. The methods of centrifugation can be used quantitatively for the assessment of protein size and shape. 

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Column Procedures Are the Most Versatile and Productive Purification Methods Electrophoresis Is Used for Resolving Mixtures Sedimentation and Diffusion Are Used for Size and Shape Determination Protein Purification Procedures... 

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