RNA blot (Northern)

The RNA blot or Northern blot (named after the DNA blot (Southern) for genomic DNA fragments) is a molecular biology technique used to separate and identify pieces of RNA. RNA molecules are separated by mass on a gel, transferred (blotted) onto a cellulose or nylon membrane, and then labelled with complementary DNA or RNA molecules. These probes are either radioactive, typically 32P, or contain labelled nucleotides, e.g. DIG-dNTPs, recognisable by antibodies. RNA molecules can be detected and roughly quantified via probe hybridisation.

The principle of the method is nicely illustrated in this diagram and this video.

Designing RNA probes

 * DNA probes, esp. using DIG-antibody detection, often give no/weak signal; RNA probes often better here
 * minimum probe length around 25 nt (anybody has a reference for this?)
 * DNA probes may be usable for both qRT-PCR and RNA blots

Lab-specific protocols

 * Endy:Northern Blot, 32P End-Labeled Probes
 * Endy:Northern blot, AlkPhos end-labeled probes