There are various methods that can be used to purify mRNA from thetotal RNAin an extract. For example, usingcolumn separation(similar to the DNA extraction method) or usingmagnetic beads, which is described below.

磁珠附带oligodT将绑定selectively to the mRNA molecules since mRNAs typically include a polyA tail. When placed in the magnetic rack the beads containing attached mRNA will be separated from the solution. We can then pipette the solution containing all the unwanted materials, and wash the beads using 80% ethanol. After several rounds of washing we can elute (separate) the mRNA molecules from the magnetic beads and transfer them to a new tube.

Magnetic beads can also be used for the purification of other molecules. Read up on thepurification of DNAto learn how the magnetic beads work.