A novel microchip electrophoresis laser induced fluorescence detection method for the assay of T4 polynucleotide kinase activity and inhibitors

Formation and Detection of Gizzerosine in Animal Feed Matrices: Progress and Perspectives

Gizzerosine is responsible for gizzard erosion and black vomit, owing to excessive gastric acid secretion in poultry. It is a biogenic amine that forms during feed processing. Gizzerosine, a derivative of histamine, is a serious threat to animal feed safety and poultry production because it is more potent after ingestion and more harmful to poultry than histamine. The difficulty of obtaining gizzerosine and the lack of simple, rapid, and sensitive in vitro detection techniques have hindered studies on the effects of gizzerosine on gizzard health and poultry production. In this review, we evaluated the natural formation and the chemical synthesis methods of gizzerosine and introduced seven detection methods and their principles for analyzing gizzerosine. This review summarizes the issues of gizzerosine research and suggests methods for the future development of gizzerosine detection methods.

Versatile fluorescence detection of T4 PNK and mRNA based on unique DNA nanomachine amplification

The development of DNA nanomachines provides a new strategy for the detection of tumor markers. In this work, an intelligent three-dimensional (3D) DNA walking machine with polynucleotide kinase (PNK) activator was designed, which was coupled with unique nanomachine formed by DNA nanowire cascade amplification reaction for versatile fluorescence detection of T4 PNK activity and messenger RNA (mRNA). When PNK exists, the free DNA walker was formed by hydrolysis cleavage of exonuclease, then the fluorophore-labeled report probe on the Au nanoparticles (NPs) was sheared during cycling cleavage reaction, thus the fluorescence signal was recovered for detection of PNK. Moreover, the DNA nanowires were produced by rolling ring amplification, then target mRNA sequentially initiated interval hybridization of hairpin probes through DNA nanowire, thus realizing DNA cascade reaction (DCR) with high "on" signal of DNA nanomachine for mRNA assay. This developed novel fluorescence nanomachine reported a new assay method with promising application for versatile targets and showed great potential for molecular-target therapies, and clinic diagnostics.

Primer-template conversion-based cascade signal amplification strategy for sensitive and accurate detection of polynucleotide kinase activity

Here, a primer-template conversion-based cascade signal amplification strategy is described for the sensitive detection of polynucleotide kinase (PNK) activity. This strategy integrated rolling circle amplification (RCA) and multiple-repeated-strand displacement amplification (MRSDA) with G-quadruplex based fluorescence lighting-up assay. A delicate dumbbell-shaped DNA probe with 5'-hydroxyl terminus was designed, in which G-quadruplex and half recognition site of nicking enzyme Nb.BbvCI were encoded in two loops respectively. Under the action of PNK, the 5' terminus on dumbbell probe was firstly phosphorylated, and then the dumbbell was cyclized with the catalyzation of T4 ligase to become the RCA template. The RCA process produced multiple copies of the prolonged primer. After that, under the assistance of nicking enzyme Nb.BbvCI, a primer-template conversion occurred, which converted the primer and template of RCA into the template and primer of the subsequent MRSDA, respectively. The MRSDA generated multiple repeated ssDNA sequences which possessed G-quadruplexes for outputting signal by lighting-up fluorescence of thioflavin T (ThT). The cascade signal amplification of RCA and MRSDA provided high detection sensitivity, and the target-dependence of template in cascade signal amplification led to a low background. The method showed excellent detection limit of 0.2 × 10^-6 U μL^-1 in buffer and 5 cells in cell lysate sample. Moreover, this method displayed favorable selectivity when interfering proteins were present. The developed strategy has good practical potential for PNK activity detection in clinical diagnosis and medical research.

Nonradioactive Assay to Measure Polynucleotide Phosphorylation of Small Nucleotide Substrates

Polynucleotide kinases (PNKs) are enzymes that catalyze the phosphorylation of the 5' hydroxyl end of DNA and RNA oligonucleotides. The activity of PNKs can be quantified using direct or indirect approaches. Presented here is a direct, in vitro approach to measure PNK activity that relies on a fluorescently-labeled oligonucleotide substrate and polyacrylamide gel electrophoresis. This approach provides resolution of the phosphorylated products while avoiding the use of radiolabeled substrates. The protocol details how to set up the phosphorylation reaction, prepare and run large polyacrylamide gels, and quantify the reaction products. The most technically challenging part of this assay is pouring and running the large polyacrylamide gels; thus, important details to overcome common difficulties are provided. This protocol was optimized for Grc3, a PNK that assembles into an obligate pre-ribosomal RNA processing complex with its binding partner, the Las1 nuclease. However, this protocol can be adapted to measure the activity of other PNK enzymes. Moreover, this assay can also be modified to determine the effects of different components of the reaction, such as the nucleoside triphosphate, metal ions, and oligonucleotides.

Supramolecular Tandem Assay for Pyridoxal-5'-phosphate by the Reporter Pair of Guanidinocalix[5]Arene and Fluorescein

Guanidinocalix[5]arene and fluorescein reporter pair has been chosen to set up a supramolecular tandem assay principle based on the differential recognition of pyridoxal-5'-phosphate (the substrate of alkaline phosphatase, ALP), pyridoxal (the product of ALP) and phosphate (the product of ALP). This supramolecular tandem assay system offers an opportunity to monitor the activity of ALP in a label-free, continuous, and real-time manner. More importantly, a calibration curve can be given for selective and quantitative detection of pyridoxal-5'-phosphate (biomarker for several diseases).