pH-Xtra

The pH-Xtra assay is a TRF-based assay to assess extracellular acidification as a measure of glycolytic activity.

Dr Ann-Cathrin Volz Dr Ann-Cathrin Volz
Application Specialist, BMG LABTECH HQs
Dr Ann-Cathrin Volz

Dr Ann-Cathrin Volz

BMG LABTECH HQs

Application Scientist

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About Ann-Cathrin Volz

Dr. Ann Cathrin Volz is a trained nutritionist with deep expertise in cell biology, biomaterials and food science. She studied Molecular Nutritional Sciences at the University of Hohenheim, where she completed her PhD developing a serum-free in vitro model of adipose tissue. During her scientific training, she combined academic biochemistry with practical laboratory work in bioengineering. After completing her doctorate, she spent two years as a postdoctoral researcher at Reutlingen University, where she focused on transferring her knowledge of tissue engineering from biomedicine to the field of in vitro agriculture. In 2020 Ann-Cathrin joined BMG LABTECH as an Applications Specialist, where she authors application notes, conducts workshops, and supports scientific customers.

Areas of Expertise

  • Cell Biology and Cell Based Assays
  • Tissue Engineering, Stem Cells and Regenerative Medicine
  • Human metabolism
  • Biomaterials
  • Biochemistry

Academic Degrees

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PhD in Biological Chemistry and Nutrition University of Hohenheim
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MSc Degree in Nutritional Sciences University of Hohenheim
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BSc Degree in Nutritional Sciences University of Hohenheim

Metabolic perturbations play a critical role in a variety of disease states and toxicities. Knowledge of the interplay between the two main cellular ATP generating pathways, glycolysis and oxidative phosphorylation, is therefore particularly informative when examining such perturbations.

Extracellular acidification assessment

The Agilent pH-Xtra assay is a time-resolved fluorescence-based assay that can assess extracellular acidification which provides data on the rate of conversion of pyruvate to lactic acid and is, therefore, a convenient measure of glycolytic activity. Such an assay is particularly informative when assessing alterations in glucose metabolism, detecting glycolytic inhibition, and as a confirmatory analysis in the identification of mitochondrial dysfunction. 

Fig.1: example of extracellular acidification curve

The pH-Xtra assay

This assay can be analyzed with the Agilent fluorescent pH-sensitive probe, pH-Xtra, and ratiometric time-resolved fluorescence detection in standard 96- and 384-well microplates. This approach overcomes the calibration and biocompatibility issues associated with some existing probes thereby allowing conventional cell culturing and assay procedures whilst also facilitating accurate quantitative analysis. In addition, spectral compatibility with MitoXpress®, the Agilent oxygen-sensitive probe, facilitates a multiplexed measurement approach providing a comprehensive metabolic assessment of test cells.

Microplate-based detection

Examples on the detection of the pH-Xtra assay assay on BMG LABTECH plate readers are discussed in the application notes: Measuring changes in cellular metabolism by monitoring extracellular acidification and oxygen consumption in real-time, Measuring mitochondrial function and glycolytic flux in 3D cell cultures and Assessment of extracellular acidification using a fluorescence-based assay.

Frequently asked questions

  • What are pH-Xtra assays?

    pH-Xtra assays are specialized homogeneous tests designed to measure the pH levels in various samples. They are primarily used in research and quality control processes to monitor acidity or alkalinity, ensuring optimal conditions for biological or chemical reactions.
  • How do microplate readers facilitate pH-Xtra assays?

    Microplate readers enable analysis of multiple samples simultaneously, providing accurate and reproducible pH measurements. They automate data collection, reduce manual errors, and enhance efficiency in laboratory workflows.
  • Are pH-Xtra assays compatible with all types of microplates?

    Most pH-Xtra assays are compatible with standard microplates such as 96-well or 384-well plates. However, it is essential to verify compatibility with specific assay kits and microplate formats recommended by the manufacturer.
  • Can pH-Xtra assays be integrated into automated laboratory workflows?

    Yes, many modern microplate readers support automation integration through compatible software and robotic systems, allowing seamless incorporation of pH-Xtra assays into high-throughput screening processes.
  • Are there specific sample types suitable for pH-Xtra testing on microplate readers?

    pH-Xtra assays can be applied to a wide range of samples including biological fluids, cell cultures, environmental samples, and chemical solutions. Compatibility depends on the specific assay kit used.
  • What readout modes can I use for pH-Xtra assays?

    Fluorescence (for fluorogenic pH indicators) and absorbance (where applicable), plus kinetic/real-time measurements depending on the reader.
  • Can I use pH-Xtra assays in living cells?

    Yes, many pH-Xtra formats are compatible with live-cell assays, provided you follow the recommended incubation times and conditions.
  • Can these assays be used for high-throughput screening?

    Yes, pH-Xtra assays are well-suited for high-throughput screening workflows on microplate readers, enabling rapid kinetics and parallel analysis.
  • How long does a typical pH measurement take?

    Kinetic readings can be taken in minutes to hours depending on the reaction; single-endpoint measurements are faster (seconds to a minute).
  • How can I ensure the accuracy of pH measurements using a microplate reader?

    Ensure proper calibration of the instrument with standard buffers before measurements. Use fresh reagents, follow assay protocols meticulously, and perform routine maintenance to maintain measurement accuracy.

 

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