# Western Blot Test: How It Works and What It Detects

## Introduction to the Western Blot Test

The western blot test is a laboratory technique used to detect the presence of a specific protein within a complex mixture of proteins extracted from cells or tissues. Developed in 1979 by Harry Towbin and refined by W. Neal Burnette in 1981, the method combines three distinct capabilities: separating proteins by size, transferring them to a solid support, and identifying a target protein using antibodies that bind with high specificity.

The name "western blot" is a playful tribute to the Southern blot, the DNA-detection method developed by Edwin Southern in 1975. When a similar approach was adapted for RNA, it became the northern blot, and when proteins were targeted, the technique was dubbed the western blot. The term "blot" refers to the process of transferring (blotting) macromolecules onto a membrane.

At its core, the western blot answers two questions simultaneously: *Is this protein present in my sample?* and *If present, how much of it is there?* Because antibodies recognize their targets with extraordinary specificity—often distinguishing between proteins that differ by a single amino acid—the western blot can identify a single protein among thousands of unrelated proteins in a crude cellular extract.

The technique is foundational in molecular biology, clinical diagnostics, and biotechnology. It is used to confirm the expression of a cloned gene, to measure changes in protein levels under different conditions, to detect post-translational modifications such as phosphorylation, and to serve as a confirmatory test for diseases including HIV infection and Lyme disease.

## Why Use a Western Blot?

Several methods exist for detecting proteins, each with distinct strengths and limitations. Understanding why a researcher or clinician chooses a western blot requires comparing it to the alternatives.

**ELISA (Enzyme-Linked Immunosorbent Assay)** is a plate-based method that detects proteins in solution. It is rapid, quantitative, and easily automated, making it ideal for screening large numbers of samples. However, ELISA provides no information about the molecular weight of the detected protein. A positive ELISA signal could come from the full-length protein, a degradation fragment, or a cross-reacting molecule of entirely different size. The [ELISA Test](/knowledge/molecular-biology/elisa-test) is excellent for high-throughput screening, but it cannot confirm that the detected molecule is the intact protein of interest.

**Mass spectrometry** identifies proteins by their mass-to-charge ratio and peptide fragmentation patterns. It is extraordinarily powerful, capable of identifying thousands of proteins in a single experiment. However, mass spectrometry requires expensive instrumentation, specialized expertise, and extensive computational analysis. It is not practical for routine diagnostic testing or for laboratories without dedicated proteomics facilities.

**The western blot** occupies a middle ground. It is more labor-intensive than ELISA but provides molecular weight information that ELISA cannot. It is less comprehensive than mass spectrometry but far more accessible, affordable, and directly quantitative for a single protein of interest. The western blot also allows researchers to assess protein integrity—a degraded protein will appear as a lower molecular weight band or a smear, alerting the investigator to sample quality issues.

The western blot is particularly valuable when antibody specificity is uncertain. Because the protein is separated by size before antibody probing, a specific antibody should produce a single band at the predicted molecular weight. If the antibody produces multiple bands or a band at an unexpected size, the result signals a problem with antibody specificity or sample preparation. This built-in quality control is absent in ELISA, where a cross-reactive antibody would simply produce a false positive signal.

## Step-by-Step [Western Blot Procedure](/blog/guides/western-blot-procedure)

The [western blot procedure](/blog/guides/western-blot-procedure) consists of five major stages: protein extraction, separation by gel electrophoresis, transfer to a membrane, blocking and antibody probing, and detection. Each stage requires careful optimization, and errors at any step can compromise the final result.

### Protein Separation by SDS-PAGE

The first step is to extract proteins from the biological sample. Cells are lysed using a buffer containing detergents, salts, and protease inhibitors. A typical RIPA (Radio-Immunoprecipitation Assay) lysis buffer contains 50 mM Tris-HCl (pH 7.4), 150 mM NaCl, 1% NP-40, 0.5% sodium deoxycholate, and 0.1% SDS (sodium dodecyl sulfate), supplemented with protease inhibitors such as phenylmethylsulfonyl fluoride (PMSF) at 1 mM and a cocktail of broad-spectrum protease inhibitors. The detergent disrupts lipid membranes, releasing proteins into solution, while protease inhibitors prevent enzymatic degradation.

The protein concentration of the lysate is then measured, typically using a Bradford or BCA (bicinchoninic acid) assay, so that equal amounts of protein can be loaded into each well of the gel. Loading equal protein amounts is essential for comparing protein levels between samples.

The protein mixture is mixed with a sample buffer containing SDS, a reducing agent such as β-mercaptoethanol or dithiothreitol (DTT), glycerol, and a tracking dye like bromophenol blue. The sample is heated to 95–100°C for 5 minutes. SDS binds to proteins at a ratio of approximately 1.4 g SDS per gram of protein, coating them with a uniform negative charge that overwhelms the protein's intrinsic charge. The reducing agent breaks disulfide bonds, denaturing the protein into its linear polypeptide chains. The result is that all proteins in the mixture become negatively charged rods whose charge-to-mass ratio is approximately constant.

The samples are loaded into wells of a polyacrylamide gel. The gel consists of two layers: a stacking gel (typically 4% acrylamide, pH 6.8) that concentrates the samples into a sharp band, and a resolving gel (typically 8–15% acrylamide, pH 8.8) where separation occurs. An electric field is applied (typically 100–150 V for 1–2 hours), and proteins migrate toward the positive electrode. Because the polyacrylamide matrix acts as a molecular sieve, smaller proteins migrate faster than larger ones. The relationship between molecular weight and migration distance is approximately logarithmic: a plot of log(molecular weight) versus migration distance yields a straight line.

The percentage of acrylamide in the resolving gel determines the range of protein sizes that can be effectively separated. A 7.5% gel separates proteins in the range of 40–200 kDa, a 10% gel separates 20–100 kDa, and a 12–15% gel is optimal for proteins below 40 kDa. For very large proteins (>200 kDa), gradient gels (e.g., 4–20% acrylamide) provide better resolution across a wide size range.

### Transfer to a Membrane

After electrophoresis, the proteins are separated by size but are embedded within the polyacrylamide gel. To make them accessible to antibodies, they must be transferred to a membrane—a thin sheet of nitrocellulose or polyvinylidene fluoride (PVDF).

Transfer is accomplished by applying an electric field perpendicular to the gel, driving the negatively charged proteins out of the gel and onto the membrane. Two transfer methods exist: wet (tank) transfer and semi-dry transfer.

In wet transfer, the gel and membrane are sandwiched between filter paper and sponges, all submerged in transfer buffer (typically 25 mM Tris, 192 mM glycine, 20% methanol, pH 8.3). The methanol helps proteins bind to the membrane by stripping away SDS, but it also causes gels to shrink and can reduce transfer efficiency for large proteins. An electric current of 100 V is applied for 1 hour, or 30 V overnight at 4°C. The cold temperature prevents overheating, which can distort the gel and cause uneven transfer.

In semi-dry transfer, the gel and membrane are placed between buffer-saturated filter papers and electrodes, and transfer occurs at higher current (e.g., 15–25 V for 30 minutes). Semi-dry transfer is faster but can be less efficient for proteins larger than 100 kDa.

After transfer, the membrane can be stained with Ponceau S, a reversible protein stain, to confirm that transfer occurred and that equal amounts of protein were loaded. Ponceau S stains all proteins as pink bands and can be washed away with water or TBST (Tris-buffered saline with Tween-20) before antibody probing.

### Blocking and Antibody Probing

The membrane now contains a replica of the protein separation pattern from the gel. However, the membrane surface also has many hydrophobic sites where antibodies could bind non-specifically. To prevent this, the membrane is incubated in a blocking solution containing an excess of irrelevant protein, typically 5% bovine serum albumin (BSA) or 5% non-fat dry milk in TBST (20 mM Tris, 150 mM NaCl, 0.1% Tween-20, pH 7.6). The blocking protein occupies the hydrophobic sites, leaving the target protein accessible for antibody binding. Blocking is performed for 1 hour at room temperature or overnight at 4°C.

The membrane is then incubated with the primary antibody—an antibody that specifically recognizes the target protein. Primary antibodies are typically used at dilutions of 1:500 to 1:10,000, depending on the antibody's affinity and concentration. Incubation is usually performed for 1–2 hours at room temperature or overnight at 4°C with gentle agitation. The antibody binds to its specific epitope—the particular region of the protein it recognizes.

After primary antibody incubation, the membrane is washed thoroughly with TBST to remove unbound antibody. Typically, three to five washes of 5–10 minutes each are performed.

The membrane is then incubated with a secondary antibody—an antibody that recognizes the constant region of the primary antibody. For example, if the primary antibody was raised in a rabbit, the secondary antibody would be an anti-rabbit antibody raised in a goat or donkey. The secondary antibody is conjugated to an enzyme, most commonly horseradish peroxidase (HRP) or [alkaline phosphatase](/knowledge/molecular-biology/alkaline-phosphatase) (AP). Secondary antibody incubation is performed for 1 hour at room temperature, followed by additional washes.

### Detection and Visualization

The final step is to visualize the antibody-bound protein. For HRP-conjugated secondary antibodies, the membrane is incubated with a chemiluminescent substrate such as enhanced chemiluminescence (ECL) reagent. HRP catalyzes the oxidation of luminol in the presence of hydrogen peroxide, producing light at 428 nm. The light emission is captured on X-ray film or, more commonly today, by a digital imaging system equipped with a cooled charge-coupled device (CCD) camera.

The signal intensity is proportional to the amount of target protein present. Exposure times typically range from seconds to several minutes. Overexposure can saturate the signal, while underexposure may fail to detect weak bands. Modern imaging systems allow multiple exposures to be captured automatically, ensuring that at least one exposure falls within the linear range of detection.

For [alkaline phosphatase](/knowledge/molecular-biology/alkaline-phosphatase)-conjugated secondary antibodies, colorimetric substrates such as BCIP (5-bromo-4-chloro-3-indolyl phosphate) and NBT (nitroblue tetrazolium) produce a purple precipitate at the site of the antibody-antigen complex. Colorimetric detection is less sensitive than chemiluminescence but requires no specialized equipment.

## How the Western Blot Detects Specific Proteins

The specificity of the western blot rests entirely on the antibody-antigen interaction. An antibody is a Y-shaped protein produced by B cells that recognizes a specific molecular structure—the epitope—with high affinity. The primary antibody used in a western blot is selected to recognize the target protein's epitope, which may be a linear sequence of amino acids (continuous epitope) or a three-dimensional structure (conformational epitope). Because SDS-PAGE denatures proteins, only antibodies recognizing linear epitopes are suitable for western blotting. Antibodies that recognize conformational epitopes may work for immunoprecipitation or immunohistochemistry but will fail in a western blot.

The detection process is a cascade of specific interactions:

1. The primary antibody binds to the target protein immobilized on the membrane.
2. The secondary antibody binds to the primary antibody. This interaction is species-specific: an anti-mouse secondary antibody binds to mouse antibodies but not to rabbit or goat antibodies.
3. The enzyme conjugated to the secondary antibody (e.g., HRP) catalyzes a reaction that produces a detectable signal.

The signal at a given position on the membrane corresponds to the presence of the target protein at that position. Because the protein's migration distance during SDS-PAGE is determined by its molecular weight, the position of the band indicates the protein's size. A band at the expected molecular weight confirms that the detected protein is the intact target, not a degradation product or a cross-reacting species.

The intensity of the band correlates with the amount of protein present. Within the linear range of detection, doubling the amount of target protein doubles the signal intensity. This relationship allows semi-quantitative analysis: comparing band intensities between samples reveals relative changes in protein expression. For absolute quantification, a standard curve can be generated using known amounts of purified recombinant protein.

## Interpreting Western Blot Results

A properly performed western blot produces a membrane with a series of bands. Interpreting these bands requires attention to several features: position, presence or absence, and intensity.

**Molecular weight markers** are a mixture of proteins of known molecular weights, loaded into a separate well on the gel and transferred to the membrane alongside the samples. After detection, the markers are visualized either by a total protein stain or by a cocktail of antibodies that recognize the marker proteins. The markers allow the researcher to determine the molecular weight of the target protein band by comparing its migration distance to the marker proteins. Most commercial markers include proteins spanning 10–250 kDa, with some prestained markers visible during transfer, allowing immediate assessment of transfer efficiency.

**[Positive and negative controls](/blog/guides/positive-and-negative-controls-how-to-choose-and-use-them)** are essential for interpreting results. A positive control is a sample known to contain the target protein—for example, a lysate from cells that overexpress the protein of interest. A positive control confirms that the antibody and detection system are working. A negative control is a sample known to lack the target protein, such as a lysate from knockout cells or a sample where the primary antibody is omitted. The negative control confirms that the signal is specific and not due to non-specific antibody binding.

A **positive result** appears as a single band at the expected molecular weight. The band should be absent in the negative control and present in the positive control. If the band appears at an unexpected molecular weight, possible explanations include:

- **Post-translational modifications**: Phosphorylation, glycosylation, or ubiquitination can alter a protein's apparent molecular weight. For example, a heavily glycosylated protein may migrate as a diffuse band at a higher molecular weight than predicted from its amino acid sequence.
- **Splice variants**: [Alternative splicing](/blog/guides/alternative-splicing) can produce protein isoforms of different sizes.
- **Proteolytic cleavage**: Degradation produces lower molecular weight fragments.
- **Cross-reactivity**: The antibody may recognize a different protein with a similar epitope.

**Multiple bands** can indicate non-specific binding, protein degradation, or the presence of multiple isoforms. The pattern of bands—whether they are sharp or diffuse, present in all samples or only some—provides clues to the cause.

**Quantitative analysis** is performed by measuring the integrated density of each band using imaging software. The signal must fall within the linear range of the detection system; saturated bands cannot be accurately quantified. To control for loading differences, the target protein signal is often normalized to a **loading control**—a housekeeping protein such as β-actin (42 kDa), GAPDH (36 kDa), or α-tubulin (50 kDa) that is expressed at constant levels across samples. The ratio of target signal to loading control signal provides a normalized measure of protein expression.

## Applications of the Western Blot Test

The western blot test has applications across clinical diagnostics, biomedical research, and biotechnology.

**Disease diagnosis**: The most famous clinical application is the confirmatory test for HIV infection. Screening is performed with an ELISA that detects antibodies against HIV proteins. Because ELISA can produce false positives, a positive screening result is confirmed by western blot. The HIV western blot detects antibodies against specific HIV proteins, including p24 (capsid), gp41 (transmembrane envelope), and gp120/gp160 (surface envelope). A positive result requires reactivity against at least two of these proteins. The western blot's ability to detect multiple specific antibodies simultaneously makes it far more specific than ELISA alone.

Similarly, the [Lyme Western Blot](/knowledge/molecular-biology/lyme-western-blot) is used to confirm Lyme disease after a positive ELISA screening. The test detects antibodies against specific Borrelia burgdorferi proteins, with the Centers for Disease Control and Prevention (CDC) requiring specific bands for a positive interpretation. The [Test of Cure Mycoplasma](/knowledge/molecular-biology/test-of-cure-mycoplasma) also relies on antibody detection methods to confirm successful treatment.

The western blot is also used in the diagnosis of [Prion Disease Lab Test](/knowledge/molecular-biology/prion-disease-lab-test) protocols, where it detects the disease-associated isoform of the prion protein (PrPSc) based on its resistance to proteinase K digestion. Normal prion protein (PrPC) is completely digested by proteinase K, while PrPSc remains intact and is detected as a band on the western blot.

**Research applications**: In basic research, the western blot is used to:

- Confirm that a gene knockdown or knockout successfully reduced protein expression.
- Measure changes in protein expression under different experimental conditions (e.g., drug treatment, stress, differentiation).
- Detect post-translational modifications using phospho-specific or acetyl-specific antibodies. For example, a [Histone Western Blot](/knowledge/molecular-biology/histone-western-blot) can detect specific histone modifications such as H3K4me3 (trimethylation of lysine 4 on histone H3) or H3K27ac (acetylation of lysine 27 on histone H3), providing insight into chromatin state and gene regulation.
- Verify the specificity of antibodies before use in other applications.
- Assess protein-protein interactions when combined with immunoprecipitation.

**Biotechnology and quality control**: The western blot is used to verify the identity and purity of recombinant proteins produced for therapeutic or research use. It can detect product-related impurities, degradation products, and host cell proteins that may contaminate the final product. Regulatory agencies such as the FDA expect biopharmaceutical manufacturers to demonstrate product consistency, and western blotting is a standard tool for this purpose.

**Biomarker discovery**: The western blot is used to validate candidate [Biomarker Test](/knowledge/molecular-biology/biomarker-test) proteins identified by mass spectrometry or microarray analysis. Western blot validation confirms that the candidate protein is genuinely differentially expressed and that antibodies against it can reliably detect the difference.

## Common Pitfalls and How to Avoid Them

The western blot is a multi-step procedure, and each step offers opportunities for error. The most common pitfalls are described below, along with troubleshooting strategies.

**Non-specific binding**: The most frequent problem is the appearance of multiple bands or high background. This typically results from insufficient blocking, excessive primary antibody concentration, or inadequate washing. Solutions include increasing blocking time or blocking protein concentration, reducing primary antibody concentration, increasing the number or duration of washes, and adding Tween-20 to all buffers. If non-specific bands persist, the antibody may be of poor quality and should be validated against a knockout or knockdown sample.

**Poor transfer**: If the target protein is not detected despite adequate loading, the transfer may have been inefficient. Large proteins (>150 kDa) transfer poorly, especially in semi-dry systems. Solutions include using wet transfer, adding SDS (0.1%) to the transfer buffer, transferring overnight at low voltage, or using a PVDF membrane instead of nitrocellulose. PVDF has a higher protein binding capacity and is more resistant to tearing.

**Air bubbles**: Air bubbles trapped between the gel and membrane during transfer create circular regions where no protein is transferred, appearing as white spots on the membrane. Rolling a pipette over the sandwich to remove bubbles before transfer prevents this problem.

**Protein degradation**: If the target protein appears as multiple lower molecular weight bands or a smear, the sample may have degraded during preparation. Protease inhibitors must be added to the lysis buffer, and samples should be kept on ice throughout preparation. For proteins that are particularly susceptible to degradation, boiling the sample immediately after lysis can inactivate residual proteases.

**Antibody incompatibility**: A primary antibody that works for immunocytochemistry or flow cytometry may not work for western blotting. As noted earlier, the antibody must recognize a linear epitope. Additionally, some antibodies are raised against native proteins and lose affinity for denatured proteins. Testing the antibody against a positive control lysate is essential before troubleshooting other variables.

**Signal saturation**: Overexposure of chemiluminescent blots produces saturated bands that cannot be quantified. The linear range of the detection system is limited; signals that are too strong or too weak fall outside this range. Solutions include reducing the amount of protein loaded, using a less sensitive substrate, or capturing multiple exposures with increasing times.

**Loading errors**: Unequal protein loading between wells produces misleading differences in band intensity. Accurate [protein quantification](/knowledge/molecular-biology/quantify-proteins) before loading, combined with a loading control antibody, helps identify and correct for loading discrepancies.

**High background**: A uniformly dark background across the entire membrane indicates excessive antibody concentration, insufficient blocking, or inadequate washing. Reducing antibody concentrations and increasing wash times usually resolves this issue.

**Edge effects**: Bands at the edges of the gel may migrate differently due to uneven heating or electric field distortion. Loading samples in the central wells and using prestained markers in the outer wells helps mitigate this problem.

## Summary and Key Takeaways

The western blot test is a powerful and versatile technique for detecting specific proteins in complex mixtures. It combines size-based separation by SDS-PAGE with the molecular specificity of antibody-antigen recognition, providing both qualitative and semi-quantitative information about protein presence, size, and abundance.

The procedure involves five essential steps: protein extraction, separation by gel electrophoresis, transfer to a membrane, blocking and antibody probing, and detection. Each step requires careful optimization, and the quality of the final result depends on the quality of the reagents, the rigor of the protocol, and the skill of the investigator.

The western blot's unique combination of specificity, molecular weight information, and accessibility has made it an indispensable tool in molecular biology, clinical diagnostics, and biotechnology. While newer technologies such as mass spectrometry offer greater throughput and comprehensiveness, the western blot remains the gold standard for confirming the presence of a specific protein and for validating antibody-based detection methods.

## Frequently Asked Questions

### What is a western blot test?

A western blot test is a laboratory technique that detects a specific protein in a complex mixture of proteins. It separates proteins by size using gel electrophoresis, transfers them to a membrane, and uses antibodies to identify the target protein. The test provides information about both the presence and the molecular weight of the protein.

### How does a western blot test work?

The western blot works by exploiting two properties of proteins: their size and their antigenicity. Proteins are first denatured and coated with SDS, giving them a uniform negative charge, then separated by size through a polyacrylamide gel. The separated proteins are transferred to a membrane, where a primary antibody binds specifically to the target protein. A secondary antibody conjugated to an enzyme binds to the primary antibody, and a substrate produces a detectable signal—typically chemiluminescence—at the location of the target protein.

### What are the steps of a western blot test?

The main steps are: (1) protein extraction from cells or tissues, (2) separation of proteins by SDS-PAGE, (3) transfer of proteins to a membrane, (4) blocking to prevent non-specific antibody binding, (5) incubation with a primary antibody specific to the target protein, (6) incubation with an enzyme-conjugated secondary antibody, and (7) detection of the signal, usually by chemiluminescence.

### What is the purpose of the western blot test?

The western blot test is used to determine whether a specific protein is present in a sample, to estimate its molecular weight, and to compare its abundance between different samples. It is used in research to study protein expression and modification, in clinical diagnostics to confirm diseases such as HIV and Lyme disease, and in biotechnology for quality control of protein products.

### Why is the western blot called 'western'?

The name is a tribute to the Southern blot, the DNA detection technique developed by Edwin Southern in 1975. When RNA detection was developed, it was called the northern blot, and when protein detection was developed, it was called the western blot. The names are whimsical references to the compass directions and have no scientific significance.

### What is the difference between western blot and ELISA?

Both techniques use antibodies to detect proteins, but they differ in their approach and information provided. ELISA is performed in solution in microtiter plates and is rapid and quantitative, but it provides no information about protein size. The western blot separates proteins by size before detection, providing molecular weight information and confirming the integrity of the target protein. ELISA is better for high-throughput screening, while the western blot is better for confirmation and detailed analysis. For more detail, see the [ELISA Test](/knowledge/molecular-biology/elisa-test) article.

### What does a positive western blot result look like?

A positive western blot result appears as a distinct band on the membrane at the expected molecular weight of the target protein. The band should be present in the positive control sample and absent in the negative control. The position of the band, determined by comparison to molecular weight markers, confirms that the detected protein has the expected size. The intensity of the band correlates with the amount of protein present.

## Key Takeaways

- The western blot test detects specific proteins in complex mixtures by combining size-based separation with antibody-based detection.
- SDS-PAGE denatures proteins and separates them by molecular weight, with smaller proteins migrating faster through the polyacrylamide gel.
- Proteins are transferred from the gel to a membrane, where they are probed with a primary antibody specific to the target protein and a secondary antibody conjugated to a detection enzyme.
- The position of the band indicates the protein's molecular weight, while the band's intensity correlates with protein abundance.
- Positive and negative controls are essential for interpreting results and confirming antibody specificity.
- The western blot is used in clinical diagnostics (including HIV and Lyme disease confirmation), biomedical research, and biopharmaceutical quality control.
- Common pitfalls include non-specific binding, poor transfer, protein degradation, and signal saturation; each can be addressed through specific troubleshooting strategies.

## Further Reading

- Pereira SR et al. *Western blot detection of [infectious bursal disease virus](/knowledge/viruses/avian-viruses/infectious-bursal-disease-virus) infection*. Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas. 1998. [PubMed 9698773](https://doi.org/10.1590/s0100-879x1998000500011)
- Turner VF. *HIV western blot test*. The Medical journal of Australia. 1994. [PubMed 8208208](https://doi.org/10.5694/j.1326-5377.1994.tb125971.x)
- Rossano MG et al. *Improvement of western blot test specificity for detecting equine serum antibodies to Sarcocystis neurona*. Journal of veterinary diagnostic investigation : official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc. 2000. [PubMed 10690772](https://doi.org/10.1177/104063870001200105)
- Su XZ, Prestwood AK. *A dot-ELISA mimicry western blot test for the detection of swine trichinellosis*. The Journal of parasitology. 1991. [PubMed 1992098](https://pubmed.ncbi.nlm.nih.gov/1992098/)
- Alcaraz C et al. *Highly specific confirmatory western blot test for African swine fever virus antibody detection using the recombinant virus protein p54*. Journal of virological methods. 1995. [PubMed 7769024](https://doi.org/10.1016/0166-0934(94)00150-f)
- Fillipo BH, Russin SJ. *What to do when results of a western blot test are indeterminate*. Postgraduate medicine. 1991. [PubMed 1994356](https://doi.org/10.1080/00325481.1991.11700839)

## Related Clinical & Scientific Guides

* [MAPK Pathway: Mechanism, Function, and Clinical Relevance](/knowledge/molecular-biology/mapk-pathway)
* [Mammalian Cell Culture Bioreactors: A Practical Guide](/knowledge/molecular-biology/mammalian-cell-culture-bioreactor)
* [Nucleotide Formation: Biosynthesis and Assembly of DNA/RNA Building Blocks](/knowledge/molecular-biology/nucleotide-formation)