The Threshold Total DNA Assay Kit

assay components

		Figure 1. Assay components for the Threshold Total DNA assay.

reaction stage

		Figure 2. Formation of a reaction complex.

A reaction complex is formed in the Total DNA Assay when biotinylated single-stranded binding protein and anti-ssDNA antibody, conjugated to urease, bind without sequence specificity to single-stranded DNA. Since binding occurs in solution, all molecules are maintained in their native conformation to assure accurate measurement of DNA and 100% activity of the binding proteins. All assay components are included in the complete Total DNA Assay Kit.

separation stage

		Figure 3. The separation stage of the Threshold Total DNA assay.

During the separation stage, the strong affinity of streptavidin for biotin is used to capture and concentrate the reaction complexes onto a biotinylated membrane by a filtration step. The Threshold® workstation contains four 8-channel filtration units, with the possibility of adding two auxiliary manifolds, for a total simultaneous filtration of 96 samples.

detection stage

		Figure 4. The detection stage of the Threshold Total DNA assay.

In the detection stage, the captured reaction complex on the membrane is placed into the Threshold reader, which contains the substrate urea and the light-addressable potentiometric sensor (LAPS). Inside the reader, urea is hydrolyzed by urease, producing a pH change in a microvolume of less than 1 µl. Urease activity from eight different samples is simultaneously detected by the sensor during a 90-second kinetic measurement. The extreme sensitivity, precision, and reproducibility of the Threshold system is due to the combination of the small sample volume with the low-noise sensor.

data analysis

Threshold software for Windows® not only controls the workstation, but also collects and analyzes data. It includes five standard curve fits to provide the highest accuracy when quantitating unknowns. A complete summary report detailing the results can be printed or exported for further analysis.

Ordering Information

Product Number	R9009	R9004
Product Name	Total DNA Assay Kit	Bulk Total DNA Assay Kit
Unit Size	1 Kit provides reagents for 64 determinations	1 Bulk Kit provides reagents for 800 determinations

To place an order, call your local Molecular Devices Office or Molecular Devices Distributor.