New England Biolabs offers several products for detection of RNA.
The p19 miRNA Detection Kit (NEB #E3312) uses the high affinity binding properties of the p19 protein to detect miRNAs that form hybrids with a specific probe. The p19 is expressed as an amino terminal fusion of the maltose binding protein (MBP) and a carboxy terminal fusion of the chitin binding domain (CBD). The MBP aids in p19 purification and the CBD allows p19 to bind very tightly to Chitin Magnetic Beads (NEB #E8036). The p19 fusion protein bound to chitin magnetic beads (p19 beads) has the same binding properties as the native p19; it selectively binds siRNAs that are 21–23 bases long but does not bind ssRNA or dsDNA of the same length (2,3). After siRNA or hybrids of miRNA:RNA-probe are bound to the p19 beads, they can easily be isolated in a small volume using a Magnetic Separation Rack (NEB #S1506) or (NEB #S1509) and eluted with SDS. The p19 beads can also enrich siRNAs greater than 3,000 fold from a mixture of total cytoplasmic RNA.
NEB’s Streptavidin Magnetic Beads (NEB #S1420) are 1 µm superparamagnetic particles covalently coupled to a highly pure form of streptavidin. Captured substrates can be useful as ligands in subsequent experiments, including mRNA isolation and the capture of primary or secondary antibodies.
(1) Silhavy, D. et al. (2002) EMBO J., 21, 3070-3080. PMID: 12065420
(2) Vargason, J.M., et al. (2003) Cell, 115, 799-811. PMID: 14697199
(3) Jin, J. et al (2010) BioTechniques, 48, XVII-XVIII. PMID: 20569217