Technical Note Methods of RNA Purification. All Ways (Should) Lead to Rome

Ribonucleic acid (RNA) represents an im- portant target of a wide array of laboratory anal yses. Thus, RNA purification is a critical first preceding step of a number of preparative and analytical meth- ods, important particularly in diagnostics of dozens of viral, bacterial, and parasitic diseases, dia gnosis of inherited disorders, and tumours, as well as in basic research. To provide relevant and reliable results, techniques of molecular biology used for such pur- poses require pure and intact molecules of purified RNA. Moreover, RNA has to be purified effectively and reproducibly from various heterogeneous mate- rials such as fresh or frozen tissues, cell lines, PCR products or long-term chemically preserved samples. Principally, methods of RNA purification can be di- vided into three groups. The first group of methods is based on organic phenol:chloroform extraction. The second group encompasses methods of RNA purifi- cation by means of its ability to bind specific surfaces in the presence of chaotropic salt, and the third group includes methods exploiting RNA isolation on iso- pycnic gradients. Although RNA can be isolated from either prokaryotic or eukaryotic organisms, this re- view is to give out a basic outline of methods availa- ble for eukaryotic, with emphasis on mammalian, tissues.