Protein Quantification
Protein Quantification - Related Videos
08:57
Peptide and Protein Quantification Using Automated Immuno-MALDI (iMALDI)
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Cited by 13 •
2017
A protocol for the protein quantification in complex biological fluids using automated immuno-MALDI (iMALDI) technology is presented.
09:04
Selected Reaction Monitoring Mass Spectrometry for Absolute Protein Quantification
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Cited by 15 •
2015
This protocol describes how to perform absolute quantification assays of target proteins within complex biological samples using selected reaction monitoring. It was used to accurately quantify proteins of the mouse macrophage chemotaxis signaling pathway. Target peptide selection, assay development, and qualitative and quantitative assays are described in detail.
06:25
Electrochemiluminescence Assay for Quantification of Target Protein Levels in Brain Lysate
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2025
In this video, we demonstrate the electrochemiluminescence immunoassay for the quantitation of target protein levels in different samples. This assay is based on the luminescence produced in the electrochemical reaction. The intensity of light emitted is proportional to the quantity of the target protein in the sample.
06:09
Quantification of Proteins Using Peptide Immunoaffinity Enrichment Coupled with Mass Spectrometry
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Cited by 37 •
2011
Stable Isotope Standards and Capture by Anti-Peptide Antibodies (SISCAPA) couples affinity enrichment of peptides with stable isotope dilution mass spectrometry (MRM-MS) to provide quantitative measurement of peptides as surrogates for their respective proteins. Here we describe the protocol using magnetic particles in a partially automated format.
11:09
An HS-MRM Assay for the Quantification of Host-cell Proteins in Protein Biopharmaceuticals by Liquid Chromatography Ion Mobility QTOF Mass Spectrometry
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Cited by 9 •
2018
Here, we describe a chromatographic assay coupled with the ion mobility separation of peptide precursors followed by the high-resolution (~30,000) MS-detection of peptide fragments for the quantification of spiked peptide standards in a monoclonal antibody digest.
FAQs
Colorimetric assays translate protein presence into a measurable absorbance change. In one approach, protein binding alters the color of a dye; in another, proteins promote the reduction of copper ions, producing a different color response. The measured absorbance reflects the assay signal, which researchers use to estimate concentration and compare protein amounts between biological samples.
A standard curve connects known protein amounts with their corresponding absorbance signals. Researchers measure the standards, establish this relationship, and then compare an unknown sample’s signal with the curve to estimate its concentration. This step converts an instrument reading into a protein measurement and supports consistent comparisons across samples and experiments.
The two approaches create measurable color through different chemical events. Dye-binding assays depend on an interaction between protein and a dye, whereas copper-reduction assays depend on protein-associated reduction of copper ions. Because their signal-generating mechanisms differ, selecting between them means matching the assay approach to the measurement being performed and the biological samples under study.
Accurate measurements allow researchers to normalize samples so that downstream experiments begin with comparable protein amounts. This consistency is important when comparing results from Western blotting, enzyme assays, or mass spectrometry. Better normalization reduces variation caused by unequal sample loading, making observed differences more likely to reflect biological changes rather than inconsistent preparation.
A typical workflow includes preparing biological samples, measuring the assay-generated absorbance, and comparing those readings with a standard curve. The resulting estimate can then guide sample normalization before a downstream experiment. Keeping the measurement and comparison process consistent helps researchers prepare equivalent protein amounts and evaluate results across samples.
Researchers use it when they need comparable protein input or want to assess changes in protein-related outcomes. It is especially relevant before Western blotting, enzyme assays, and mass spectrometry, where inconsistent sample amounts can complicate interpretation. The measurement can also support evaluations of protein expression and purification yield.
Beyond preparing equal inputs, the results can support comparisons of protein expression, purification yield, and cellular function. A measured concentration provides a basis for examining whether protein amounts differ among biological samples or experimental conditions. In this way, quantification links a sample measurement to broader questions about protein production, recovery, and biological activity.