Close the electrophoresis unit and connect it to a power supply.

The ladder will allow you to monitor protein separation during electrophoresis and subsequently verify protein weight in your sample during later analysis.

Load your samples into the wells and load a pre-stained molecular weight ladder into one well.

Rinse the wells of the gel with a running buffer and add a buffer to the chambers.

Prepare your gel by inserting it into the electrophoresis apparatus and filling it with a running buffer that is appropriate for your gel chemistry.

Therefore higher percentage of gels are better for low molecular weight proteins, a low percentage of gel are useful for large proteins and gradient gels can be used for proteins of all sizes due to their varying range in pore size. The higher the acrylamide percentage the smaller the pore size of the gel matrix. Gels are available in fixed percentages or gradients of acrylamide. To do this, we load our previously prepared protein samples into a commercially available polyacrylamide gel. In this step, we will separate the individual proteins in our sample lysate based on their molecular weight using a positive electrode to attract a negatively charged protein. Now the sample is ready to load into an SDS page gel. Vortex each sample and incubate at 95 degrees Celsius for five minutes to completely denature the proteins.

bromophenol blue to visualize the lysate and an ionic buffer.

glycerol to allow the samples to sink into each well,.

SDS to assist in denaturing and to provide a net negative charge to the protein,.beta-mercaptoethanol, or DTT, to reduce disulfide bridges between cysteines,.To reduce and denature samples dilute each in a loading buffer such as Laemmli sample buffer.

These conditions will allow proteins to be separated by their molecular weight rather than their native conformational shape or charge. Western blots are typically performed under reduced and denatured conditions. The supernatant is the lysate which we will use for further processing. The cell mixture is centrifuged and the pellet is discarded. Cells are lysed by incubating on ice and later applying shear pressure using a pipette. Lysis buffer should contain protease inhibitors to prevent the degradation of the protein of interest. (The choice of lysis buffer largely depends on the localization of the protein of interest, solubilization of membrane-bound proteins requires stronger extraction detergents compared with isolated cytoplasmic proteins).Īlways use freshly prepared protease inhibitors, keep samples on ice and work quickly. Take the sample, add ice-cold PBS and lysis buffer such as RIPA buffer which is a commonly used buffer for maximum protein yield. Western blotting procedures include the following steps: Tissue Preparation (preparation of sample lysate):

Western blot technique