Understanding How to extract biologically active proteins from the cells

Extraction of proteins from cells and tissue of organisms is the first step towards isolation of proteins. The extracellular matrix needs to be removed or digested in case of tissue, the cell wall needs to be digested for organisms like bacteria, yeast and plants, and the cell membrane needs to be disrupted to release the proteins in solution. Traditionally, physical methods for disruption of cells and tissues are employed to release cellular proteins including sonication, french press, homogenization, manual grinding or using blenders.  Although one is able to get the active proteins, these physical methods have several limitations:

• Expensive
• Cumbersome due to use of heavy equipment
• Reduced yield as the sample is processed through several steps
• Batch to batch variation in protein yield due variability and handling

Mechanical methods can sometimes denature proteins as these methods are harsh and some of them generate heat and can denature protein if appropriate cooling of sample is not done.

Chemical methods for cell disruption using lysis buffers with ionic detergents can be used to release proteins; however they can denature the protein.  Non-ionic detergents offer advantage over lysis buffer and ionic detergents as they are mild and the proteins are not denatured. Therefore, nowadays popular methods for extraction of biologically active proteins from cells or tissues use non-ionic detergents along with other additives, such as enzymes for cell wall disruption and addition of protease inhibitors to inhibit proteases. This method may involve mild mechanical methods, including brief homogenizing or vortexing depending upon the cell or tissue type.