How many times have we seen bands from IgG heavy or light chains interfering with our bands of interest? Typically the source of this problem is the secondary antibody we use. Secondary antibodies are directed against the IgG class or subclass of the species in which the primary antibody was raised. In general, they react with both the IgG heavy and light chain.
Besides the desired binding to the primary antibody, heavy and light chain–specific secondary antibodies tend to bind to heavy and light chains of endogenous immunoglobulin molecules present in reduced or denatured western blot samples. In addition to the endogenous IgGs, primary antibodies of the IgG isotypes are also released from beads during immunoprecipitation (IP) procedures. Bands from IgG heavy (~50 kD) and light (~25 kD) chains often mask or obstruct the bands of interest in a western blot of immunoprecipitated proteins.
How do you avoid visualization of IgG heavy or light chains when your immunoprecipitated protein of interest has a molecular weight close to 25 or 50 kD?
The best way to avoid this problem is to use a secondary antibody or a detection reagent that binds only to the native nondenatured antibodies rather than to any IgG present in the sample. This is a sure way to reduce or eliminate the problem of background band detection in western blots. The new detection reagent from Bio-Rad, TidyBlot™ Western Blot Detection Reagent, does exactly that. It is HRP conjugated and binds exclusively to the native nondenatured IgG antibody used for western blot detection and thereby binds only to the IgG of interest. The result is a cleaner western blot, as the IgG heavy and light chain bands do not show up (see Figures 1, 2, and 3 below).
Here are some fun band detection exercises to challenge your western blot–trained eyes:
1. Do you or do you not see the band at 25 kD representing the GSTP1 protein in lane 5?
The following western blot was generated to detect the 25 kD GSTP1 protein. The experimental procedure described in the figure caption was followed except that the TidyBlot Secondary Detection Reagent was used in lane 2 and an HRP-conjugated anti-mouse IgG (heavy and light chain) secondary antibody was used in lane 5. Can you see the 25 kD GSTP1 band hidden behind the IgG band in lane 5?
2. Find the band at 50 kD representing the SSB protein in lane 4.
The following western blot was generated to detect the 50 kD SSB (also known as Lupus La) protein. The experimental procedure described in the figure caption was followed except that the TidyBlot Western Blot Detection Reagent was used for the detection of SSB in lane 2 and an HRP-conjugated anti-mouse IgG (heavy and light chain) secondary antibody was used for lane 4. Can you find the 50 kD SSB protein band hidden behind the IgG band in lane 4?
How do you tackle the problem of visualizing endogenous IgGs when using tissue lysate samples?
The TidyBlot Reagent works across a broad range of species and detects both monoclonal and polyclonal antibodies and makes background-free western blotting a reality.
For more information and to view the FAQs, visit https://www.abdserotec.com/tidyblot.
The primary antibody used in western blotting can cause considerable detection of background signals, requiring several optimization steps to reduce the background. For extensively validated western blotting antibodies that eliminate the need for time-consuming optimization to reduce background, explore the PrecisionAb Antibodies at https://www.abdserotec.com/validated-western-blotting-antibodies-precisionab.html.