The Invader Assay

Smith and coworkers combined this genotyping method, which is operates directly on genomic DNA, with MALDI-MS analysis. In a reaction called the Invader Squared assay, the primary cleavage product serves as an Invader molecule for a second Invader reaction. The squared cleavage product is then purified via streptavidin-biotin, which allows separation and conditioning of the cleavage products for MALDl-TOF-MS [167]. 

Direct Analysis ofSNPs From Human Genomic DNA 

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Kwiatkowski RW, Lyamichev V, de Arruda M, Neri B. Clinical, genetic, and pharmacogenetic applications of the Invader assay. Mol Diagn 1999 4(4) 353-364. 

Cooksey RC, Holloway BP, Oldenburg MC, Listenbee S, Miller CW. Evaluation of the invader assay, a linear signal amplification method, for identification of mutations associated with resistance to rifampin and isoniazid in Mycobacterium tuberculosis. Antimicrob Agents Chemother 2000 44(5) 1296-1301. 

Hsu, T.M. Law, S.M. Duan, S. Neri, B.P. Kwok, P.-Y. Genotyping single-nucleotide polymorphisms by the invader assay with dual-color fluorescence polarization detection. Clin. Chem. 2001, 47, 1373-1377. 

Invader Assay. The Invader assay developed by Third Wave Technologies, Inc. (Madison, WI) is an attractive FRET-based technique to genotype SNPs without PCR amplification (Figure 7.5-5). Two oligonucleotides, a wild-type or variant signal probe plus an upstream Invader probe, are used in each reaction. These... 

Figures, a. Mechanism of the Invader assay, b. The Invader squared reaction.

The first attempts to enable gene expression analysis by MS were reported only recently, when Smith and coworkers appHed the Invader assay (see Section 5.4.1.5 and Figure 5.12) to the detection and relative quantification of RNA [224]. In order to allow an inter-spectrum (and thus inter-sample) correlation. Invader assays of multiple target genes were multiplexed and a reference gene was included for normalization of the data. 

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