RESUMEN
Alkaline phosphatase(ALP)is widely expressed in human tissues.ALP plays an important role in the dephosphorylation of proteins and nucleic acids.Therefore,quantitative analysis of ALP plays a vital role in disease diagnosis and the development of biological detection methods.Terminal deoxynucleotidyl transferase(TdT)catalyzes continuous polymerization of deoxynucleotide triphosphates at the 3'-OH end of single-stranded DNA in the absence of a template.In this study,we developed a highly sensitive and selective method based on TdT and endonuclease Ⅳ(Endo Ⅳ)to quantify ALP activity.After ALP hydrolyzes the 3'-PO4 end of the substrate and generates 3'-OH,TdT can effectively elongate the 3'-OH end with deoxynucleotide adenine triphosphate(dATP)and produce a poly A tail,which can be detected by the poly T probes.Endo Ⅳ digests the AP site in poly T probes to generate a fluorescent signal and a new 3'-OH end,leading to the generation of exponential fluorescence signal amplification.The substrate for TdT elongation was optimized,and a limit of detection of 4.3×10-3 U/L was achieved for ALP by the optimized substrate structure.This method can also detect ALP in the cell lysate of a single cell.This work has potential applications in disease diagnosis and biomedical detection.
RESUMEN
Genetic mutations are important molecular biomarkers for cancer diagnosis and surveillance.Therefore,the development of methods for mutation detection characterized with straightforward,highly specific and sensitive to low-level mutations within various sequence contexts is extremely needed.Although some of the currently available methods have shown very encouraging results,their discrimination efficiency is still very low.Herein,we demonstrate a fluorescent probe coupled with blocker and property of melting temperature discrimination,which is able to identify the presence of known or unknown single-base variations at abundances down to 0.1％ within 20 min.The discrimination factors between the perfect-match target and single-base mismatched target are determined to be 10.15-38.48.The method is sequence independent,which assures a wide range of application.The new method would be an ideal choice for high-throughput in vitro diagnosis and precise clinical treatment.