Real-time kinase & phosphatase monitoring.
Direct. Continuous. No coupled enzymes.
No antibodies, radioisotopes, or wash steps.
A new review in RSC Chemical Biology independently benchmarks SOX-labelled peptide technology against mass spectrometry, immunoassays, radioactivity-based methods, and FRET reporters — and names AssayQuant’s PhosphoSens® as the commercially available implementation of the gold standard platform. Unlike coupled enzyme assays or endpoint immunoassays, PhosphoSens® delivers a direct fluorescent readout of kinase activity in real time — in purified enzyme or unfractionated cell lysates.
Request a feasibility discussion Read the review →Papagora & Cochrane, RSC Chem. Biol., 2026. DOI: 10.1039/d6cb00048g
Independent validation
What an independent academic review concluded
Published in May 2026 by researchers at Queen’s University Belfast, this focused review evaluated SOX (sulfonamido-oxine) peptide technology across three generations of sensor design — comparing it head-to-head against every major class of kinase assay currently in use.
“SOX-peptides allow direct, continuous measurement of kinase and phosphatase activity, providing access to kinetic information that is difficult to obtain using conventional endpoint assays… these tools offer a practical alternative to antibody- and radioactivity-based methods, particularly for studies in unfractionated lysates and inhibitor screening.”
— Papagora & Cochrane, RSC Chemical Biology, 2026
The review specifically named AssayQuant’s PhosphoSens® platform as the commercially available implementation of this technology — noting its ability to deliver direct, real-time kinase activity readouts without coupling enzymes, antibodies, or wash steps, and its compatibility with purified recombinant enzymes and unfractionated cell and tissue lysates.
What the review found wrong with existing approaches
All findings above are drawn directly from Papagora & Cochrane, RSC Chemical Biology, 2026 — an independent peer-reviewed assessment with no commercial affiliation.
Platform advantages
What PhosphoSens® does differently
The review documents six distinct advantages of continuous SOX-based assays over every alternative method currently in use. Each addresses a specific failure mode of conventional approaches.
Direct measurement
PhosphoSens® reports kinase activity via a direct fluorescent readout — not a downstream surrogate. No coupling enzymes that can be inhibited by your compounds or introduce additional variables.
Truly continuous
Full progress curves, not a single timepoint snapshot. Capture KM, Vmax, and PK/PD parameters from a single run — and see everything endpoint formats miss.
Catches time-dependent inhibition
TDI is accurately resolved because the full reaction curve is observed. Critical for covalent and slow-binding inhibitor programs where endpoint formats routinely mischaracterize potency.
No antibodies or wash steps
Homogeneous, mix-and-read format. No batch-to-batch antibody validation. No discontinuous sampling. No radioactivity handling. Run it the same way every time.
Works in cell lysates
Directly measure endogenous kinase activity in unfractionated cell and tissue lysates with less than 0.1 mg total cell protein — no purification required.
Flexible plate formats & readout modes
Run in 96-, 384-, or 1536-well formats. Choose between PhosphoSens-Kinetic for continuous real-time fluorescence intensity, or PhosphoSens-Red for time-resolved fluorescence (TRF) endpoint — reducing compound autofluorescence interference in complex samples.
What is time-dependent inhibition? TDI occurs when a compound’s potency changes over the course of the reaction — common with covalent and slow-binding inhibitors. An endpoint assay takes a single snapshot and can entirely miss it, or worse, mischaracterize the inhibitor’s mechanism. A continuous assay watches the full reaction curve in real time, so TDI is caught and accurately quantified every time.
Validated assay performance
Kinase & phosphatase coverage
Targets validated in this review
The targets below are specifically cited with validated SOX-sensor sequences in the review. AssayQuant’s PhosphoSens® catalog covers 500+ kinase and 45+ phosphatase assays — see the full list below.
Targets above cited in Papagora & Cochrane, RSC Chem. Biol. 2026. See all 500+ PhosphoSens® assays →
Ready to add continuous kinase data to your program?
Whether you’re profiling inhibitors, characterizing enzyme kinetics, or building a lysate-based screening workflow, our team can scope the right assay format for your target and sample type.
