Measuring the purity of mRNA can be done by measuring its absorbance at 260 nm. An absorbance of 1.0at 260 nm is equivalent is equivalent to 40 mg mRNA. An additional reading at 280 nm allows the A260:A280 ratio to be calculated. A ratio of 2.0 should be expected.
The integrity of the mRNA can be assessed by gel electrophoresis. The mRNA should appear on ethidium bromide-stained gel as a smear ranging from 200 bp to greater than 10 kb with no detectable ribosomal RNA. If small amounts of mRNA are added to the gel, visualization by ethidium bromide may be impossible. In order to cicumvent the problem, set up a Northern blot and hybridize using a labeled oligo(dT) primer. Autoradiography should reveal mRNA fragments ranging in size