Lumigen APS-5 utilizes a unique technology for the chemiluminescent detection of alkaline phosphatase conjugates and provides superior sensitivity and ease of use. Reaction of the acridan substrate with an AP label produces sustained high-intensity chemiluminescence. Lumigen APS-5 is ideally suited for solution assays of phosphatase activity and for phosphatase-linked immunoassays.

An Applications Note illustrating the sensitivity of Lumigen APS-5 in the detection of alkaline phosphatase on a microplate luminometer is available from Turner BioSystems.

• Excellent sensitivity -- less than 10^-19 moles AP can be measured.
   
• Rapid develpment of peak signal reduces assay time and increases throughput.
   
• Linear calibration curves with slopes of log-log plots equal to 1.0 -- one order of magnitude more enzyme yields one order of magnitude more light.
   
• Sustained luminescence -- timing is less critical. Light intensities can be read at any time to produce linear calibration curves.
   
• Analytical results are insensitive to temperature from 22°C to 35°C reducing the need for precise temperature control.
   

A sandwich immunoassay for thyroid stimulating hormone (TSH) performed with an Immulite TSH Third Generation TSH Assay kit yielded a linear plot from 0.003 to 75 mIU/L with good assay precision. Lumigen APS-5 was substituted for the normal dioxetane substrate, Lumigen PPD.

The image below from a western blot analysis of human transferrin was made after a 10 min incubation of the PVDF membrane with Lumigen APS-5 with a 1 min exposure to X-OMAT film. Equivalent results were obtained using nitrocellulose membranes. No other chemiluminescent reagent allows complete interchangeability of blotting membrane.