Protein Quantitation
Protein Quantitation - Related Videos
11:12
Identification of protein complexes with quantitative proteomics in S. cerevisiae
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Cited by 4 •
2009
Here we describe a new quantitative proteomics technique for identifying protein complexes in Saccharomyces cerevisiae. In this study, we have used the SILAC method together with affinity purification followed by tandem mass spectrometry to identify with high specificity the binding partners of an ER protein, Scs2p.
10:50
Qualitative and Quantitative Assays for Detection and Characterization of Protein Antimicrobials
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Cited by 11 •
2016
Here, we present protocols to rapidly screen and characterize enzymes for antimicrobial activity. The microslide diffusion assay and the dye-release assay utilize target bacterial substrates for qualitative and quantitative enzymatic activity evaluation.
06:02
Quantitative Western Blotting to Estimate Protein Expression Levels
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2025
The video demonstrates a total protein normalization-based western blotting technique for quantifying the target protein expression in a sample. By utilizing the total protein staining of the sample, a ratiometric analysis is performed to determine the relative expression level of the target protein.
07:54
Heterogeneity Mapping of Protein Expression in Tumors using Quantitative Immunofluorescence
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Cited by 27 •
2011
Here we describe a method to quantify molecular heterogeneity in histological sections of tumor material using quantitative immunofluorescence, image analysis, and a statistical measure of heterogeneity. The method is intended for use in clinical biomarker development and analysis.
04:39
Quantitative Dot Blot to Estimate Target Proteins in a Tissue Lysate
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2025
This video demonstrates a quantitative dot blot, or QDB, technique for the absolute quantification of proteins of interest in a tissue sample. The proteins in the sample are immobilized on the nitrocellulose membrane inside the wells of a QDB plate. Utilizing target protein-specific antibodies labeled with a peroxidase enzyme, a chemiluminescent substrate is oxidized to produce light, which is measured to determine the protein concentration of the sample.
FAQs
Colorimetric assays convert protein-related chemical interactions into a measurable color change. The resulting signal is compared with measurements from standards containing known protein concentrations, allowing the concentration of an unknown biological sample to be estimated. This approach provides a consistent basis for comparing samples and preparing equivalent protein amounts for later analyses.
Bradford assays rely on protein–dye binding, whereas bicinchoninic acid assays use a chemical reaction that produces color in response to protein. Both methods support concentration measurements through comparison with a standard curve, but they represent different assay chemistries. This distinction gives researchers more than one colorimetric approach for quantitating proteins in biological experiments.
A standard curve links measured color intensity to known protein concentrations. Researchers use that relationship to interpret the signal from an unknown sample rather than relying on color alone. Because the curve provides the concentration reference, it supports consistent comparisons among samples and helps standardize the amount of protein introduced into downstream biological assays.
Normalization adjusts samples so that downstream comparisons reflect biological differences rather than unequal protein loading. In practice, measured concentrations can guide preparation of comparable sample amounts for gel electrophoresis, Western blotting, or enzyme assays. This improves experimental reproducibility and makes differences in subsequent measurements easier to interpret across biological samples.
A typical workflow prepares standards with known protein concentrations, applies a colorimetric assay to the standards and biological samples, and measures the resulting color signals. The sample measurements are then compared with the standard curve to estimate concentration. Those results can guide sample normalization before gel electrophoresis, Western blotting, or enzyme assays.
Researchers use these measurements whenever experiments require comparable protein input or concentration-based interpretation. Applications include preparing samples for gel electrophoresis, Western blotting, and enzyme assays, as well as supporting work in cell biology, biochemistry, disease studies, and biotechnology. Reliable concentration estimates help connect sample preparation with reproducible experimental outcomes.
The principal output is an estimated total protein concentration for each biological sample. Researchers can use that information to compare samples, determine whether loading amounts are comparable, and organize subsequent analyses around standardized protein input. In studies involving cells, biochemical reactions, disease-related samples, or biotechnology workflows, this measurement strengthens interpretation by reducing variation from sample amount.