Nucleic Acids Research, Vol 27, Issue 19 e25-e25, Copyright © 1999 by Oxford University Press
SR White and TK Christopoulos
The development of hybridization assays based on an apoaequorin- encoding
DNA label is reported. The constructed label contains the T7 RNA polymerase
promoter, the apoaequorin coding sequence and a downstream (dA/dT)(30). In
the captured target configuration, biotinylated target DNA (233 bp) was
captured on streptavidin-coated microtiter wells and hybridized to a
poly(dT)-tailed detection probe. In the sandwich-type assay, the target DNA
was hybridized simultaneously with an immobilized capture probe (through
biotin/streptavidin) and a poly(dT)-tailed detection probe. In both
configurations, the hybrids were reacted with poly(dA)-tailed apoaequorin
DNA. The DNA label was subjected to in vitro transcription/translation to
produce apoaequorin, which was converted to active aequorin in the reaction
mixture. Generated aequorin was determined by its characteristic
Ca(2+)-triggered bioluminescence. Each DNA label was estimated to produce
156 aequorin molecules. As low as 0.25 and 0.5 amol of target DNA were
detected with the sandwich-type and captured target hybridization assays,
respectively, with a linear range spanning four orders of magnitude. In
comparison, captured target hybridization assays using photoprotein
aequorin or firefly luciferase- encoding DNA labels were able to detect 25
and 20.5 amol of target DNA, respectively. The dramatic improvement in
sensitivity observed with the proposed systems is attributed to
amplification introduced by in vitro expression of apoaequorin DNA into
multiple active aequorin molecules.
ARTICLES
Signal amplification system for DNA hybridization assays based on in vitro expression of a DNA label encoding apoaequorin
Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada.
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