A ''turn-off'' SERS assay for kinase detection based on arginine N-phosphorylation process.

A sequential "turn-off" surface enhance Raman scattering (SERS) assay platform for the detection of protein arginine kinase McsB is constructed based on arginine N-phosphorylation process. The positive charged peptide initiates the aggregation of labelled Au nanoparticles (AuNPs) to form ''Hot Spots'', resulting to a higher SERS intensity. However, the aggregation of AuNPs could also be disbanded by the addition of McsB in which the peptides are phosphorylated on arginine residues, leading to the sharp decline of SERS signal, on account of two negative charges on the phosphate group. By this strategy, a novel ''turn-off'' SERS biosensor for McsB detection based on arginine N-phosphorylation was established with high sensitivity, selectivity and simplicity. Compared with other non-enzymatic amplification methods, the sensitivity of this newly demonstrated method was improved effectively. The detection limit for McsB is 46 pM. Besides, some controlled experiments show that the assay possesses good selectivity, which is mainly decided by the specificity of kinase. Since some kinases are important biomarkers, this assay could make great contribution in biomarkers detection in complex matrices which is based on signal amplification.