How Long Does It Take To Do a Western Blot
The western blot method is used to detect specific proteins in complex biological samples. It works through three main steps:
- Separation of proteins by size using gel electrophoresis
- Transfer of proteins onto a membrane
- Detection using antibodies
This method has remained a key tool in protein research since it was introduced in 1979 by Harry Towbin and later named by Neal Burnette in 1981. It’s still widely used today.
A traditional workflow may take about a day or two, while the newly developed workflows may reduce this time by about 3–4 hours, depending on the situation.
Sample Preparation
- Cells: Washed with cold phosphate-buffered saline, then lysed using buffers such as RIPA or NP-40 for about 30 minutes at 4°C
- Tissues: Require mechanical breakdown (about 3 minutes), followed by 2 to 5 hours of mixing to help release proteins more completely
After extraction, the samples are then centrifuged at high speed (12,000 to 16,000 × g for around 20 minutes) to remove debris and other unwanted material.
Protein Quantification
Protein concentration needs to be measured before moving forward.
- Bradford assay: Fast (about 5 minutes), good for quick checks
- BCA assay: More accurate in the presence of detergents, but takes about 30 minutes at 37°C or sometimes up to 2 hours at room temperature
This step usually adds somewhere around 1 to 1.5 hours to the workflow.
Denaturation
Proteins are prepared for separation by unfolding them.
- Mixed with Laemmli buffer containing SDS
- Heated at 95 to 100°C for about 5 minutes
- Membrane proteins are handled more gently at around 70°C for 10 minutes to avoid aggregation
Altogether, sample preparation typically takes about 2 to 4 hours in most cases.
Gel Electrophoresis
At this stage, proteins are separated based on size using an electric field.
- Under normal circumstances, this takes about 100-150 volts over 60-90 minutes.
- If faster techniques are employed, the whole procedure could be over in about 20 minutes.
Precast gels are usually the preferred choice as they reduce the time needed as well as the chance of exposure to harmful substances.
Protein Transfer
Separated proteins are moved from the gel onto a membrane (usually nitrocellulose or PVDF).
- Wet transfer: 1 to 2 hours, generally more reliable for larger proteins
- Semi-dry transfer: about 30 to 60 minutes
- Rapid systems: as fast as 3 to 10 minutes
- Dry systems: roughly 7 minutes, and no external buffer is needed
The choice here mostly depends on available equipment and how quickly results are needed.
Immunodetection
Blocking
The membrane is treated to prevent unwanted antibody binding.
- Standard time: about 1 hour
- Faster systems: closer to 30 minutes
Antibody Incubation
- Primary antibody:
- About 1 hour at room temperature for high-affinity antibodies
- Often left overnight at 4°C for low-abundance targets
- Secondary antibody:
- Around 1 hour at room temperature
Washing steps follow each stage, usually about 3 to 5 washes at roughly 10 minutes each. Altogether, this can add around 1 to 1.5 hours, sometimes a bit more.
Detection and Imaging
Two methods of detection are chemiluminescence and fluorescence.
Chemiluminescence:
- Incubate the substrate for 1-5 minutes.
- The signal decays after a couple of hours.
- The imaging may take anywhere from a few seconds to a few minutes.
Fluorescence:
- Allows to detect more than one protein at once.
- The signal remains stable for a long time, even for months if stored properly.
- No need to strip and reprobe, which saves time
Final Takeaway
The western blot method is a multi-step workflow, which can take anywhere from a few hours to two days, depending on the protein of interest and the way the workflow is set up.
While doing it manually offers flexibility and reduces the overall cost, automated systems offer speed and reliability. It is observed that the final results are largely affected by the decisions made at each step in the Western blotting process.
