Discover Your Next Enzyme Activity Assay
PhosphoSens-Kinetic assays leverages AssayQuant’s Proprietary Detection Technology to provide real-time, continuous measurements of kinase activity by directly detecting substrate phosphorylation throughout the kinase reaction.
Sensor Peptide Substrates are developed with our readout molecule, Sulfonamido-oxine (Sox), covalently attached via a cysteine residue (native or introduced) in close proximity to the Serine, Threonine, or Tyrosine phosphorylation site (± 2-5 residues).
The Sox fluorophore reports peptide phosphorylation by the target kinase via chelation-enhanced fluorescence (ChEF). The fluorescence-sensing mechanism is based on the chelate effect introduced by phosphorylation of the Ser/Thr/Tyr residue proximal to CSox, which enhances magnesium (Mg²⁺) binding affinity compared to the unphosphorylated species, and results in increased fluorescence emission intensity (2-10-fold).
In this way, CSox-modified peptide substrates provide a fluorescent intensity signal that is directly proportional to the phosphorylation level of the substrate, enabling continuous/real-time kinetic measurements of kinase activity in medium to high throughput (96−1536 well plate).