Loading Controls for Western Blotting

What are Loading Controls?

Loading controls are proteins that are highly constitutively expressed in a sample and are used as a positive control in protein blotting experiments. These proteins are used as a reference to normalize variations in protein loading between different samples, allowing for accurate and reliable quantification of the protein of interest.

The choice of loading control antibody depends on the specific experimental conditions and the protein of interest. Commonly used loading controls include β-actin, histone 3, GAPDH, α-tubulin, vinculin, and other common housekeeping proteins required for basic cellular functions. These proteins are commonly found in most sample types, and their abundance is typically unaffected by biological variation. Depending on the experimental conditions, different antibodies may be more appropriate, so the choice of loading controls is worth careful consideration.

When selecting a loading control, the following key criteria need to be considered:

• A loading control is a protein used in Western blotting as a reference to ensure that the protein of interest is being detected accurately. To be a suitable loading control, the protein level should remain constant despite any changes resulting from assay treatments or developmental stages.
• The loading control should have a substantially different molecular weight compared to the protein of interest.
• It is important to choose a loading control that is expressed strongly in the sample of interest.
• The abundance of the loading control protein should be comparable to that of the protein of interest in the sample to ensure that changes in protein levels can be accurately detected without signal saturation. If the signal is not in the linear range, the results may be inaccurate or difficult to interpret. Therefore, it is essential to optimize the detection method and adjust sample dilutions to ensure that both the loading control and the protein of interest fall within this linear range.

Troubleshooting Common Issues with Loading Control Antibodies

Despite careful optimization and validation, loading control antibodies can sometimes result in unexpected or inconsistent results. Here are some common issues with loading control antibodies and some troubleshooting tips:

• High Background Signal
  The high background signal can be caused by non-specific binding of the loading control antibody to other proteins in the sample. To reduce the background signal, try reducing the concentration of the loading control antibody or increasing the washing steps.
• Weak or Non-Detectable Signal
  The weak or non-detectable signal can be caused by insufficient protein loading or transfer, or by low sensitivity of the loading control antibody. To increase the signal intensity, try increasing the protein loading amount or optimizing the transfer conditions. If the loading control is not sensitive enough, try using a more sensitive detection method or a different loading control.
• Inconsistent Signal
  Inconsistent signals can be caused by variations in protein loading or transfer efficiency. To improve consistency, try using a more accurate protein quantification method or optimizing the transfer conditions.

By following these tips for optimizing loading control antibody usage and troubleshooting common issues, researchers can ensure Western blotting experiments are accurate and reliable.

Creative Diagnostics offers a wide range of high-quality loading control antibodies validated under a variety of experimental conditions. Our loading controls are an excellent choice for your experiments because they are appropriate for multiple sample types, and cover a wide range of molecular weights. With their expertise and commitment to quality, Creative Diagnostics is a trusted partner for molecular biology researchers.