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Choose total protein normalization approaches based on quantitative accuracy, reproducibility, and western blot analysis requirements. Compare total protein normalization and housekeeping protein controls to improve data normalization, reduce variability, and support reliable quantitative western blot results. This page is for laboratories seeking improved normalization accuracy and reproducible protein analysis without relying on housekeeping protein controls.
Explore the western blot workflow
What is total protein normalization?
Total protein normalization (TPN) is a widely used western blot normalization method that uses the total amount of protein in each lane as the loading control. TPN helps improve quantitative accuracy by accounting for sample loading and transfer variability without relying on housekeeping proteins. Unlike housekeeping protein controls, TPN measures the total protein signal in each lane rather than a signal protein target, helping provide a more consistent basis for quantitative western blot analysis.
Total protein normalization is typically performed after protein transfer and before or alongside western blot detection and quantitative analysis, helping ensure accurate and reproducible protein quantitation.
Solution for total protein normalization
No-Stain Protein Labeling Reagent is a versatile protein labeling reagent that enables rapid protein visualization in gels or transferred membranes in as little as 10 minutes. It supports multiple protein analysis workflows, including direct protein visualization as an alternative to traditional gel stains, assessment of protein transfer efficiency following transfer, and total protein normalization for quantitative western blot analysis. Compatible with chemiluminescent and fluorescent workflows, No-Stain Protein Labeling Reagent offers sensitive, linear protein detection across a broad range of sample loads.
Use No-stain Protein Labeling Reagent when you need to:
- Perform accurate total protein normalization for quantitative western blot analysis
- Directly visualize proteins in a gel as an alternative to traditional gel stains
- Assess protein transfer efficiency from the gel to the membrane after transfer
- Housekeeping protein expression may vary under experimental conditions
- Rapid protein labeling and analysis are preferred
- Quantitatively compare protein expression across samples
Use the table below to evaluate key workflow characteristics and determine whether No-Stain Protein Labeling Reagent is appropriate for your western blot workflow.
Why use total protein normalization instead of housekeeping proteins?
Total protein normalization |
Housekeeping proteins |
Uses total protein signal |
Uses a single protein control |
Less affected by biological variation |
Expression may vary |
Broader linear range |
May require optimization to maintain linearity |
No additional antibody required |
Requires housekeeping protein antibody |
How does the No-Stain Protein Labeling Reagent work?
No-Stain Protein Labeling Reagent enables rapid protein labeling in gels or transferred membranes in as little as 10 minutes. The reagent forms stable covalent bonds with proteins, helping provide sensitive, linear protein detection for protein visualization, assessment of transfer efficiency, and total protein normalization workflows (Figure 1). Following labeling, proteins can be imaged directly and used in downstream chemiluminescent or fluorescent western blot applications. Labeling conditions can also be adjusted to increase signal intensity when greater sensitivity is required.
Figure 1. No-Stain Protein Labeling Reagent workflow. Proteins can be labeled on either gels or transferred membranes in approximately 10 minutes, enabling rapid protein visualization, assessment of transfer efficiency, and total protein normalization before downstream western blot detection and analysis.
The No-Stain Protein Labeling Reagent is compatible with chemiluminescent western blot workflows and can also be used in multiplex fluorescent western blot workflows with near-infrared (nIR) and infrared (IR) secondary antibodies. The No-Stain label exhibits two excitation peaks (~380 nm and ~488 nm), enabling imaging with either UV or blue/green excitation sources and providing broad compatibility with commonly used western blot imagers and gel documentation systems. When designing multiplex experiments, select fluorophores with excitation and emission spectra that do not overlap with the No-Stain label to help achieve clear signal separation and accurate quantitation (Figure 2).
Figure 2. Excitation and emission spectra of the covalently linked No-Stain label. The No-Stain label has an excitation maximum of approximately 488 nm and an emission maximum of 590 nm. The spectra show that the signal from the No-Stain label can be imaged using a UV or fluorescent light source and the signal can be captured with a wide range of emission filters. Understanding these spectra helps when selecting compatible near-infrared (nIR) and infrared (IR) fluorescent secondary antibodies for multiplex western blot workflows.
Use the resources below to identify compatible fluorophores and design multiplex western blot experiments.
How-to video
How do I perform total protein normalization for quantitative western blotting?
Total protein normalization helps improve the accuracy and reproducibility of quantitative western blot analysis. In this video, you'll learn how to label proteins using No-Stain Protein Labeling Reagent and perform total protein normalization using the iBright Imaging System.
You'll learn how to:
- Label proteins using No-Stain Protein Labeling Reagent
- Analyze total protein signals using the iBright Imaging System
- Normalize western blot data using total protein signals
- Perform accurate quantitative western blot analysis
No-stain protein labeling reagent performance
No-stain labels proteins within minutes
No-Stain Protein Labeling Reagent labels proteins in as little as 10 minutes, enabling rapid protein visualization and total protein normalization. The resulting protein signal remains linear across a broad range to protein loads, supporting accurate quantitative western blot analysis (Figure 3).
Figure 3. No-Stain Protein Labeling Reagent shows a linear response on membranes. A Bolt 4–12% Bis-Tris Plus mini gel was loaded with HeLa lysate ranging from 1 to 50 µg, and PageRuler Unstained Protein Ladder in lane 1. After electrophoresis, proteins were transferred onto a PVDF membrane using the Invitrogen PowerBlotter and PowerBlotter Select Stacks (10 mins). The No-Stain labeling reaction was initiated by the addition of the No-Stain Labeling Solution and allowed to proceed for 10 minutes. The image was captured using an iBright Imager with the No-Stain Membrane epi setting (455—485 nm excitation and 565—615 emission).
Quantitative protein visualization and gel staining
No-Stain Protein Labeling Reagent enables a linear relationship between protein load and signal intensity, supporting accurate quantitative protein visualization directly in gels (Figure 4).
Figure 4. Quantitative protein visualization using the No-Stain Protein Labeling Reagent. A Bolt 4–12% Bis-Tris Plus mini gel was loaded with HeLa lysate concentrations ranging from 2.5 to 80 µg and electrophoresed with MES running buffer. After electrophoresis, the proteins in the gel were labeled following the No-Stain Protein Labeling Reagent protocol for labeling proteins in a gel, and the gel was imaged using an iBright imager with the transilluminator for excitation (490–520 nm) and the 565–615 nm emission filter.
No-Stain reagent linearity versus housekeeping proteins
Protein normalization is critical for accurate quantitative western blot analysis and can be performed using housekeeping proteins, exogenous controls, or total protein normalization. Total protein normalization using No-Stain Protein Labeling Reagent measures the total protein signal in each lane, reducing the need for housekeeping protein antibodies while supporting quantitative western blot workflows.
An ideal loading control should maintain a linear relationship between signal intensity and protein load. No-Stain Protein Labeling Reagent allows highly linear total protein signals across a broad range of protein loads on both PVDF and nitrocellulose membranes. In contrast, commonly used housekeeping protein signals may require optimization and can lose linearity at higher protein loads, reducing quantitative accuracy (Figures 5 and 6).
Figure 5. No-Stain Protein Labeling Reagent helps provide a more linear relationship between protein load and signal intensity than commonly used housekeeping proteins. Bolt 4–12% Bis-Tris Plus gels were loaded with HeLa lysate ranging from 10 to 50 µg. Proteins from the gels were transferred onto PVDF membranes using the Invitrogen iBlot 2 Gel Transfer Device with iBlot 2 Transfer Stacks, PVDF, mini. The PVDF membranes were labeled with No-Stain labeling solution, followed by immunoblotting for β-actin, GAPDH, and α-tubulin followed by goat anti-mouse Alexa Fluor Plus 680. Labeling was performed following the manufacturers' recommended western blot dilution. (A) The blot was imaged using the iBright imager. (B) The iBright software was used to quantitate the total protein signal in the lanes. The linear regression value of the plotted data for the entire load range using the No-Stain Protein Labeling Reagent was determined (R2 = 0.9990), whereas the R2 values for β-actin, GAPDH, and α-tubulin were 0.8851, 0.9438, and 0.8332, respectively.
Figure 6. No-Stain Protein Labeling Reagent supports accurate quantitative western blot analysis. A Novex 4–12% Tris-Glycine gel, WedgeWell format, was loaded and electrophoresed with lysates from HeLa cells expressing RB1, at total protein loads ranging from 0.6 to 10 µg. Proteins from the gel were transferred to a nitrocellulose membrane using the iBlot 2 Dry Blotting System. The nitrocellulose membrane was labeled using the No-Stain Protein Labeling Reagent for 10 minutes. (A) The labeled membrane was imaged using the iBright imager. The same No-Stain labeled membrane was used to probe RB1 with a specific antibody labeled with Alexa Fluor 645 dye. (B) The iBright normalization software was used to quantify the total protein signal in lanes loaded with HeLa lysate loads ranging from 0.6 to 10 µg and signal intensities from RB1 immunodetection bands. The signal intensity from the total protein load and RB1 were plotted.
Increase detection sensitivity with labeling time and reagent concentration
Detection sensitivity can be optimized by increasing either the incubation time or the concentration of No-Stain Protein Labeling Reagent to improve the detection of low-abundance proteins. Increasing the incubation time of gels or blots labeled with the No-Stain Labeling Reagent increases signal intensity while maintaining a linear response (Figure 7). Alternatively, when time is limited, increasing the reagent concentration can support similar improvements in signal intensity with a shorter labeling time (Figure 8). Combined with adjustable exposure settings on iBright imaging systems, these options help provide flexibility for optimizing protein detection across a wide range of protein expression levels.
Figure 7: Increasing the incubation time of No-Stain Protein Labeling Reagent improves detection sensitivity. Transferred PVDF (polyvinylidene fluoride) membranes, incubated with No-Stain Labeling Reagent for 10, 20, 30 and 40 minutes respectively, show increased signal intensity over time. Invitrogen NuPAGE 4–12% Bis-Tris gels were loaded with E.Coli lysate ranging from 40 to 1.25 μg and separated by electrophoresis using MES SDS running buffer. Proteins from the gels were transferred onto mini PVDF membranes using the Invitrogen iBlot 2 Gel Transfer Device with iBlot 2 Transfer Stacks (P0 protocol for 7 minutes). The PVDF membranes were quickly rinsed with 20 mL of ultrapure water and incubated with 10 mL of a working solution of No-Stain Protein Labeling Reagent on a rotating platform. Analysis images, without brightness and contrast adjustment, of the blots were collected using the Invitrogen iBright FL1500 Imaging System after 10, 20, 30, and 40 minutes after addition of the No-Stain Protein Labelling Reagent (exposure time 1.000 seconds). Longer exposure times will result in stronger signals allowing for improved detection of low-expressed proteins (A). A linear correlation between the normalized signal intensity plotted against the incubation time can be observed (B).
Figure 8. Doubling the concentration of No-Stain Protein Labeling Reagent increases the sensitivity of the detection. Invitrogen Bolt 4–12% Bis-Tris Plus gels were loaded with A431 lysate (20 μg to 20 ng serial dilutions) in Bolt LDS sample buffer and separated by electrophoresis using MES SDS running buffer. Proteins were labeled with 1x or 2x No-Stain Labeling Reagent directly in the gel. 1X No-Stain Labeling Reagent was prepared according to the No-Stain Protein Labeling Reagent standard protocol. 2X No-Stain Protein Labeling Reagent was prepared by doubling the concentration of No-Stain Activator (40 μL) and No-Stain Derivatizer (40 μL). Analysis images, without brightness and contrast adjustment, of gels (A) and membranes (B) were collected using the Invitrogen iBright FL1500 Imaging System (exposure time 1.000 seconds).
No-Stain reagent compatibility with downstream western blotting
No-Stain Protein Labeling Reagent is compatible with downstream western blot workflows such as protein transfer and immunoblotting. Proteins labeled before transfer can be transferred to PVDF membranes and detected using standard immunoblotting protocols without affecting protein transfer or antibody-based detection (Figure 9).
Figure 9. No-Stain Protein Labeling Reagent is compatible with protein transfer and immunoblotting. Invitrogen Bolt 4–12% Bis-Tris Plus gels were loaded with A431 lysate (20 μg to 20 ng serial dilutions) in Bolt LDS sample buffer and separated by electrophoresis using MES SDS running buffer. The gels were incubated with No-Stain Protein Labeling Reagent for 10 minutes on a rotating platform. No-Stain Labeled gels were transferred to PVDF membranes using the Invitrogen iBlot 2 Gel Transfer Device with iBlot 2 Transfer Stacks (P0 protocol for 7 minutes). PVDF membranes were then probed with specific primary antibodies and proteins were detected using secondary antibodies labeled with the Alexa Fluor 800 dye. Analysis images, without brightness and contrast adjustment, were collected using the Invitrogen iBright FL1500 Imaging System (exposure time 1.000 seconds).
As sensitive as Coomassie staining in a fraction of the time
No-Stain Protein Labeling Reagent offers protein detection sensitivity comparable to Coomassie staining while enabling rapid protein visualization (Figure 10), making it a convenient alternative for many protein visualization workflows.
Figure 10. The sensitivity of No-Stain Protein Labeling Reagent is comparable to Coomassie staining. Invitrogen Bolt 4–12% Bis-Tris Plus gels were loaded with A431 lysate (20 μg to 20 ng serial dilutions). Protein bands were either labeled with No-Stain Protein Labeling Reagent or stained with Coomassie. Analysis images, without brightness and contrast adjustment, were collected using the Invitrogen iBright FL1500 Imaging System (exposure time 1.000 seconds). Additionally, the exposure time of the No-Stain image could be increased to allow for improved detection of even lower lysate loads compared to Coomassie.
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Frequently asked questions
Total protein normalization (TPN) is a western blot normalization method that uses the total protein signal in each lane as a loading control. By accounting for differences in sample loading and transfer efficiency, TPN helps improve the accuracy and reproducibility of quantitative western blot analysis.
Total protein normalization is increasingly preferred for quantitative western blotting because it uses the total protein signal in each lane rather than relying on a single housekeeping protein. This approach can improve normalization accuracy, reduce variability caused by changing housekeeping protein expression, and minimize the need for additional normalization antibodies.
The optimal loading control depends on the application and experimental design. For quantitative western blotting, total protein normalization is often recommended because it measures the total protein content in each lane and is less susceptible to biological variation than individual housekeeping proteins.
Yes. Total protein normalization can be used alongside chemiluminescent western blot detection workflows. No-Stain Protein Labeling Reagent is compatible with downstream chemiluminescent detection and can be used before target protein detection and analysis.
Yes. Total protein normalization can be used with fluorescent and chemiluminescent western blot workflows. No-Stain Protein Labeling Reagent is compatible with selected fluorescent secondary antibodies and can be used for quantitative analysis and total protein normalization on the same blot.
No. Total protein normalization measures the total protein signal in each lane and does not require housekeeping protein antibodies for normalization. This can simplify workflows, reduce reagent costs, and minimize the need for stripping and re-probing membranes.
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