Comparison of Classical P81 and SVI-P Cation-Exchange Papers in Radiometric Protein Kinase Assays

Radiometric kinase assays have been widely used due to their high sensitivity and dynamic range. The assay measures the transfer of 32Pi from [γ-32P]-ATP to specific substrates, typically synthetic peptides. The 32P-phosphorylated peptide product is captured by binding it to phosphocellulose paper, specifically P81. Unfortunately, GE Healthcare, the sole supplier of P81, has discontinued its manufacture. Recently, a replacement for P81, SVI-P cation-exchange filter paper, has become available. We have tested SVI-P in various kinase assays, including those for AMPK, Abl, CDK2, and ERK, and found that it performs comparably to P81 in capturing substrates. Additionally, a commercial kinase profiling assay using SVI-P successfully captured a range of peptide and protein substrates from 48 different protein kinases. One minor limitation of SVI-P was the higher background radioactivity; however, this can be addressed through optimisation and extended wash steps. Overall, SVI-P represents a viable alternative for radiometric kinase assays, ensuring continued reliability in both academic and industrial research settings.