The Protein Man's Blog | A Discussion of Protein Research

What is the Role of the Isoelectric Point of a Protein in its Purification?

Posted by Protein Man on Jul 24, 2012 6:29:00 AM


What is the role of the isoelectric point of a protein in its purification and how does it come into play with your protein purification and extraction buffer products?  

The Protein Man Says:

Protein purification includes a series of processes to isolate a particular protein from a complex mixture. This technique is critical for characterizing the function, structure, and interaction of the protein of interest. An analytical purification generally uses three distinct properties to separate proteins, including the isoelectric technique.  

protein purification, protein isoelectric pointA protein can be purified according to its protein isoelectric point by running the said protein through an ion exchange column or a pH-graded gel. At the isoelectric point, a protein has no net charge. Above the isoelectric point, a protein carries a net negative charge—below it, a net positive charge.  

Because a majority of weakly acid remains in nearly every protein, they are generally negatively charged at neutral pH. The isoelectric point is significant in protein purification because it represents the pH where solubility is typically minimal. Here, the protein isoelectric point signifies where mobility in an electro-focusing system is zero—and, in turn, the point where the protein will collect.  

To purify proteins using the isoelectric focusing method, mix a uniform protein solution with a specific polymer. This polymer has unique properties to ensure that proteins form a pH gradient when you apply an electric field across the solution. When this pH gradient is in development, protein molecules simultaneously migrate in the solution until these molecules reach their protein isoelectric point. This convenient method thus purifies complex protein mixtures by helping proteins reach their respective isoelectric points.

G-Biosciences specializes in various Protein Purification Kits, Extraction Buffers, and IEF reagents that help in the above process. Our FOCUS Chaotropic Extraction Buffers preserve the native charge of proteins during solubilization, while our Protein Purification kits use isoelectric point and other protein properties to purify proteins from bacterial and yeast cultures, among others. For more information, review our Sample Preparation, Protein Purification and Protein Electrophoresis Handbooks.

Topics: Protein Purification