How do I assess the purity and quality of purified mRNA?

The purity and quality of purified mRNA can be assessed in several ways. One way is to evaluate the 28S:18S rRNA ratio using an Agilent 2100 bioanalyzer. A ratio around 2.0 indicates high RNA quality, but lower ratios can still be acceptable, particularly if other quality indicators are good. Another way is using denaturing agarose gel electrophoresis to check rRNA band integrity; crisp 28S and 18S bands suggest good RNA quality. Another way is to carry out stability tests by incubating a small RNA sample at 37°C for several hours and comparing it with a sample stored at -20°C. A minimal decrease in the 28S:18S ratio indicates good purity and stability. Another way is through absorbance measurements at specific wavelengths. The A260/A280 ratio is particularly important, with an ideal ratio typically being 1.8>2.2. This ratio reflects the level of protein contamination in the RNA sample; a value below 1.8 suggests significant protein contamination. The A260/A230 ratio is also crucial, with an ideal ratio generally >1.7. Lower ratios than this suggest that contaminants such as guanidine thiocyanate or phenol are present.  mRNA quality through applications like Northern blotting, real-time PCR, or cDNA synthesis can also be assessed.