Extracellular Protein Assays
Extracellular Protein Assays - Related Videos
03:14
An Assay for Bacterial Extracellular Protein-Mediated Cytotoxicity on PMNs
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2025
This video demonstrates an assay to investigate the cytotoxicity of proteins produced by Staphylococcus aureus, a pathogenic bacterium, on isolated human polymorphonuclear leukocytes (PMNs). The secreted cytotoxic proteins form pores on the PMN cell membrane, initiating cell death. Upon staining the dead cells using propidium iodide, flow cytometry is performed to quantify the dead cells and assess the cytotoxicity of the bacteria.
04:39
Extracellular Flux Assay: A Method for Measuring Metabolic Profile of Cells
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2023
This protocol provides a biochemical approach for measuring extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) of primary leukemic cells with extracellular flux assay. The assessment of the metabolic profile of these cells helps to characterize their demands, leading to personalized therapy.
08:46
Strategic Endothelial Cell Tube Formation Assay: Comparing Extracellular Matrix and Growth Factor Reduced Extracellular Matrix
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Cited by 19 •
2016
This manuscript describes a tube formation assay to quantify the effects of a given compound or condition on angiogenesis by using endothelial cell tube formation in a controlled environment.
02:29
Microdialysis of Interstitial Fluid from a Mouse Brain to Isolate Extracellular Proteins
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2025
The video demonstrates the process of using a microdialysis probe to collect extracellular proteins from the interstitial fluid (ISF) of a mouse brain. A microdialysis probe, equipped with a high-molecular-weight cut-off semi-permeable membrane, is inserted into the brain of an anesthetized mouse via an implanted guide cannula. The probe, connected to pumps, allows a physiological buffer to perfuse the brain tissue and mix with the ISF. Proteins in the ISF diffuse across the semi-permeable...
06:15
Assessing the Metabolic Activity of Whole Regenerating Zebrafish Ventricles Ex Vivo Using an Extracellular Flux Assay
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2026
In this article, we describe a detailed protocol for quantifying the oxygen consumption rate and extracellular acidification rate of ex vivo adult zebrafish ventricles to characterize their oxidative and glycolytic metabolic capacity.
FAQs
Selectivity arises when a capture or detection antibody recognizes the intended protein rather than unrelated molecules in the sample. This antibody-antigen interaction allows the assay to distinguish a target cytokine, chemokine, antibody, microbial protein, or other biomarker within serum, plasma, or culture medium. Greater target specificity makes the measured signal more directly interpretable as evidence of that protein’s presence.
In these assays, the colorimetric, fluorescent, or luminescent signal is designed to vary with the amount of target protein present. A stronger signal therefore indicates a higher measured concentration under the assay conditions, while a weaker signal indicates less target. This relationship enables comparisons among biological samples and supports quantitative assessment of immune or infection-associated changes.
Colorimetric, fluorescent, and luminescent readouts provide alternative ways to convert antibody-antigen recognition into measurable data. The essential principle remains the same: target recognition produces a signal whose magnitude relates to protein concentration. Selecting among these formats allows investigators to match the detection approach to the assay design and the type of quantitative comparison required across samples.
The identity of the measured protein determines which biological process the result may illuminate. Cytokines and chemokines can report immune communication, antibodies can reflect immune responses, and microbial proteins can provide information about pathogen-related activity. Measuring these distinct target classes helps connect extracellular protein changes with cell signaling, pathogen-host interactions, treatment responses, or disease progression.
Common sample types include serum, plasma, and cell culture supernatants. Serum and plasma provide information from biological fluids, whereas culture supernatants allow analysis of proteins released by cells under experimental conditions. Choosing between them depends on whether the study aims to examine systemic disease-related changes or protein release from cells in a controlled research model.
A typical workflow identifies the target protein, applies a capture or detection antibody that recognizes it, and measures the resulting colorimetric, fluorescent, or luminescent signal. The signal is then related to the target’s concentration in the tested sample. This workflow can be applied to serum, plasma, or culture supernatants to compare extracellular protein levels across experimental conditions.
They are useful when investigators need to characterize immune activation, pathogen-host interactions, treatment responses, or disease progression through released proteins. For example, measuring cytokines, chemokines, antibodies, or microbial proteins can reveal changes in immune signaling or infection-associated biology. Results from these assays provide molecular measurements that complement broader observations of cellular or disease responses.